use bool in assert (#12170)

examples/flutter_gallery/lib/gallery/home.dart

@@ -186,7 +186,7 @@ class GalleryHomeState extends State<GalleryHome> with SingleTickerProviderState
     assert(() {
       showPreviewBanner = false;
       return true;
-    });
+    }());
 
     if (showPreviewBanner) {
       home = new Stack(

examples/flutter_gallery/lib/gallery/item.dart

@@ -331,7 +331,7 @@ List<GalleryItem> _buildGalleryItems() {
       ),
     );
     return true;
-  });
+  }());
 
   return galleryItems;
 }

examples/stocks/lib/main.dart

@@ -114,7 +114,7 @@ class StocksAppState extends State<StocksApp> {
       debugPaintPointersEnabled = _configuration.debugShowPointers;
       debugRepaintRainbowEnabled = _configuration.debugShowRainbow;
       return true;
-    });
+    }());
     return new MaterialApp(
       title: 'Stocks',
       theme: theme,

examples/stocks/lib/stock_settings.dart

@@ -199,7 +199,7 @@ class StockSettingsState extends State<StockSettings> {
         ),
       ]);
       return true;
-    });
+    }());
     return new ListView(
       padding: const EdgeInsets.symmetric(vertical: 20.0),
       children: rows,

packages/flutter/lib/src/animation/animation_controller.dart

@@ -284,7 +284,7 @@ class AnimationController extends Animation<double>
         );
       }
       return true;
-    });
+    }());
     _direction = _AnimationDirection.forward;
     if (from != null)
       value = from;
@@ -312,7 +312,7 @@ class AnimationController extends Animation<double>
         );
       }
       return true;
-    });
+    }());
     _direction = _AnimationDirection.reverse;
     if (from != null)
       value = from;
@@ -349,7 +349,7 @@ class AnimationController extends Animation<double>
           );
         }
         return true;
-      });
+      }());
       final double range = upperBound - lowerBound;
       final double remainingFraction = range.isFinite ? (target - _value).abs() / range : 1.0;
       simulationDuration = this.duration * remainingFraction;
@@ -399,7 +399,7 @@ class AnimationController extends Animation<double>
         );
       }
       return true;
-    });
+    }());
     return animateWith(new _RepeatingSimulation(min, max, period));
   }
 
@@ -483,7 +483,7 @@ class AnimationController extends Animation<double>
         );
       }
       return true;
-    });
+    }());
     _ticker.dispose();
     _ticker = null;
     super.dispose();

packages/flutter/lib/src/animation/animations.dart

@@ -405,7 +405,7 @@ class CurvedAnimation extends Animation<double> with AnimationWithParentMixin<do
           );
         }
         return true;
-      });
+      }());
       return t;
     }
     return activeCurve.transform(t);

packages/flutter/lib/src/cupertino/route.dart

@@ -131,7 +131,7 @@ class CupertinoPageRoute<T> extends PageRoute<T> {
         'Cannot install a subsidiary route (one with a hostRoute).\n'
         'This route ($this) cannot be installed, because it has a host route ($hostRoute).'
       );
-    });
+    }());
     super.install(insertionPoint);
   }
 
@@ -238,7 +238,7 @@ class CupertinoPageRoute<T> extends PageRoute<T> {
         );
       }
       return true;
-    });
+    }());
     return result;
   }
 

packages/flutter/lib/src/cupertino/tab_view.dart

@@ -136,7 +136,7 @@ class CupertinoTabView extends StatelessWidget {
         );
       }
       return true;
-    });
+    }());
     final Route<dynamic> result = onUnknownRoute(settings);
     assert(() {
       if (result == null) {
@@ -148,7 +148,7 @@ class CupertinoTabView extends StatelessWidget {
         );
       }
       return true;
-    });
+    }());
     return result;
   }
 }

packages/flutter/lib/src/foundation/assertions.dart

@@ -222,7 +222,7 @@ class FlutterError extends AssertionError {
       // In checked mode, we ignore the "silent" flag.
       reportError = true;
       return true;
-    });
+    }());
     if (!reportError && !forceReport)
       return;
     if (_errorCount == 0 || forceReport) {

packages/flutter/lib/src/foundation/binding.dart

@@ -77,7 +77,7 @@ abstract class BindingBase {
   @mustCallSuper
   void initInstances() {
     assert(!_debugInitialized);
-    assert(() { _debugInitialized = true; return true; });
+    assert(() { _debugInitialized = true; return true; }());
   }
 
   /// Called when the binding is initialized, to register service
@@ -145,8 +145,8 @@ abstract class BindingBase {
         }
       );
       return true;
-    });
-    assert(() { _debugServiceExtensionsRegistered = true; return true; });
+    }());
+    assert(() { _debugServiceExtensionsRegistered = true; return true; }());
   }
 
   /// Whether [lockEvents] is currently locking events.

packages/flutter/lib/src/foundation/change_notifier.dart

@@ -54,7 +54,7 @@ class ChangeNotifier extends Listenable {
         );
       }
       return true;
-    });
+    }());
     return true;
   }
 
@@ -63,7 +63,7 @@ class ChangeNotifier extends Listenable {
   /// This method must not be called after [dispose] has been called.
   @override
   void addListener(VoidCallback listener) {
-    assert(_debugAssertNotDisposed);
+    assert(_debugAssertNotDisposed());
     _listeners.add(listener);
   }
 
@@ -88,7 +88,7 @@ class ChangeNotifier extends Listenable {
   /// registrations to a common upstream object.
   @override
   void removeListener(VoidCallback listener) {
-    assert(_debugAssertNotDisposed);
+    assert(_debugAssertNotDisposed());
     _listeners.remove(listener);
   }
 
@@ -100,7 +100,7 @@ class ChangeNotifier extends Listenable {
   /// This method should only be called by the object's owner.
   @mustCallSuper
   void dispose() {
-    assert(_debugAssertNotDisposed);
+    assert(_debugAssertNotDisposed());
     _listeners = null;
   }
 
@@ -121,7 +121,7 @@ class ChangeNotifier extends Listenable {
   /// See the discussion at [removeListener].
   @protected
   void notifyListeners() {
-    assert(_debugAssertNotDisposed);
+    assert(_debugAssertNotDisposed());
     if (_listeners != null) {
       final List<VoidCallback> localListeners = new List<VoidCallback>.from(_listeners);
       for (VoidCallback listener in localListeners) {

packages/flutter/lib/src/foundation/debug.dart

@@ -25,7 +25,7 @@ bool debugAssertAllFoundationVarsUnset(String reason, { DebugPrintCallback debug
         debugDefaultTargetPlatformOverride != null)
       throw new FlutterError(reason);
     return true;
-  });
+  }());
   return true;
 }
 

packages/flutter/lib/src/foundation/platform.dart

@@ -45,7 +45,7 @@ TargetPlatform get defaultTargetPlatform {
     if (debugDefaultTargetPlatformOverride != null)
       result = debugDefaultTargetPlatformOverride;
     return true;
-  });
+  }());
   if (result == null) {
     throw new FlutterError(
       'Unknown platform.\n'

packages/flutter/lib/src/gestures/arena.dart

@@ -271,7 +271,7 @@ class GestureArenaManager {
         debugPrint('Gesture arena ${pointer.toString().padRight(4)} ❙ $message${ count != null ? " with $count member$s." : ""}');
       }
       return true;
-    });
+    }());
     return true;
   }
 }

packages/flutter/lib/src/gestures/binding.dart

@@ -89,7 +89,7 @@ abstract class GestureBinding extends BindingBase with HitTestable, HitTestDispa
         if (debugPrintHitTestResults)
           debugPrint('$event: $result');
         return true;
-      });
+      }());
     } else if (event is PointerUpEvent || event is PointerCancelEvent) {
       result = _hitTests.remove(event.pointer);
     } else if (event.down) {

packages/flutter/lib/src/gestures/debug.dart

@@ -54,6 +54,6 @@ bool debugAssertAllGesturesVarsUnset(String reason) {
         debugPrintRecognizerCallbacksTrace)
       throw new FlutterError(reason);
     return true;
-  });
+  }());
   return true;
 }

packages/flutter/lib/src/gestures/multidrag.dart

@@ -163,7 +163,7 @@ abstract class MultiDragPointerState {
   void dispose() {
     _arenaEntry?.resolve(GestureDisposition.rejected);
     _arenaEntry = null;
-    assert(() { _pendingDelta = null; return true; });
+    assert(() { _pendingDelta = null; return true; }());
   }
 }
 

packages/flutter/lib/src/gestures/recognizer.dart

@@ -98,7 +98,7 @@ abstract class GestureRecognizer extends GestureArenaMember with DiagnosticableT
           debugPrint('$prefix$this calling $name callback.${ report?.isNotEmpty == true ? " $report" : "" }');
         }
         return true;
-      });
+      }());
       result = callback();
     } catch (exception, stack) {
       FlutterError.reportError(new FlutterErrorDetails(

packages/flutter/lib/src/material/app.dart

@@ -504,7 +504,7 @@ class _MaterialAppState extends State<MaterialApp> {
         );
       }
       return true;
-    });
+    }());
     final Route<dynamic> result = widget.onUnknownRoute(settings);
     assert(() {
       if (result == null) {
@@ -516,7 +516,7 @@ class _MaterialAppState extends State<MaterialApp> {
         );
       }
       return true;
-    });
+    }());
     return result;
   }
 
@@ -569,7 +569,7 @@ class _MaterialAppState extends State<MaterialApp> {
         );
       }
       return true;
-    });
+    }());
 
     return new ScrollConfiguration(
       behavior: new _MaterialScrollBehavior(),

packages/flutter/lib/src/material/debug.dart

@@ -38,6 +38,6 @@ bool debugCheckHasMaterial(BuildContext context) {
       );
     }
     return true;
-  });
+  }());
   return true;
 }

packages/flutter/lib/src/material/dropdown.dart

@@ -226,7 +226,7 @@ class _DropdownMenuRouteLayout<T> extends SingleChildLayoutDelegate {
         assert(menuTop + menuHeight <= size.height);
       }
       return true;
-    });
+    }());
     return new Offset(buttonRect.left.clamp(0.0, size.width - childSize.width), menuTop);
   }
 

packages/flutter/lib/src/material/material.dart

@@ -394,7 +394,7 @@ abstract class InkFeature {
   @mustCallSuper
   void dispose() {
     assert(!_debugDisposed);
-    assert(() { _debugDisposed = true; return true; });
+    assert(() { _debugDisposed = true; return true; }());
     _controller._removeFeature(this);
     if (onRemoved != null)
       onRemoved();

packages/flutter/lib/src/material/material_localizations.dart

@@ -282,7 +282,7 @@ class DefaultMaterialLocalizations implements MaterialLocalizations {
         );
       }
       return true;
-    });
+    }());
 
     return _icuTimeOfDayToEnum[icuShortTimePattern];
   }

packages/flutter/lib/src/material/page.dart

@@ -134,7 +134,7 @@ class MaterialPageRoute<T> extends PageRoute<T> {
         );
       }
       return true;
-    });
+    }());
     return result;
   }
 

packages/flutter/lib/src/material/paginated_data_table.dart

@@ -85,7 +85,7 @@ class PaginatedDataTable extends StatefulWidget {
          if (onRowsPerPageChanged != null)
            assert(availableRowsPerPage != null && availableRowsPerPage.contains(rowsPerPage));
          return true;
-       }),
+       }()),
        assert(source != null),
        super(key: key);
 

packages/flutter/lib/src/material/stepper.dart

@@ -626,7 +626,7 @@ class _StepperState extends State<Stepper> with TickerProviderStateMixin {
           'https://material.google.com/components/steppers.html#steppers-usage\n'
         );
       return true;
-    });
+    }());
     assert(widget.type != null);
     switch (widget.type) {
       case StepperType.vertical:

packages/flutter/lib/src/material/tabs.dart

@@ -546,7 +546,7 @@ class _TabBarState extends State<TabBar> {
         );
       }
       return true;
-    });
+    }());
     if (newController == _controller)
       return;
 
@@ -855,7 +855,7 @@ class _TabBarViewState extends State<TabBarView> {
         );
       }
       return true;
-    });
+    }());
     if (newController == _controller)
       return;
 
@@ -1113,7 +1113,7 @@ class TabPageSelector extends StatelessWidget {
         );
       }
       return true;
-    });
+    }());
     final Animation<double> animation = new CurvedAnimation(
       parent: tabController.animation,
       curve: Curves.fastOutSlowIn,

packages/flutter/lib/src/painting/flutter_logo.dart

@@ -162,7 +162,7 @@ class FlutterLogoDecoration extends Decoration {
     assert(debugAssertIsValid());
     if (a is! FlutterLogoDecoration)
       return lerp(null, this, t);
-    assert(a.debugAssertIsValid);
+    assert(a.debugAssertIsValid());
     return lerp(a, this, t);
   }
 

packages/flutter/lib/src/painting/text_painter.dart

@@ -367,7 +367,7 @@ class TextPainter {
         );
       }
       return true;
-    });
+    }());
     canvas.drawParagraph(_paragraph, offset);
   }
 

packages/flutter/lib/src/painting/text_span.dart

@@ -275,7 +275,7 @@ class TextSpan extends DiagnosticableTree {
         );
       }
       return true;
-    });
+    }());
     return true;
   }
 

packages/flutter/lib/src/rendering/binding.dart

@@ -86,7 +86,7 @@ abstract class RendererBinding extends BindingBase with SchedulerBinding, Servic
           }
       );
       return true;
-    });
+    }());
 
     registerSignalServiceExtension(
       name: 'debugDumpRenderTree',

packages/flutter/lib/src/rendering/block.dart

@@ -98,7 +98,7 @@ class RenderListBody extends RenderBox
         'axis. You probably want to put the RenderListBody inside a '
         'RenderViewport with a matching main axis.'
       );
-    });
+    }());
     assert(() {
       switch (mainAxis) {
         case Axis.horizontal:
@@ -123,7 +123,7 @@ class RenderListBody extends RenderBox
         'for example, a RenderIntrinsicWidth or RenderIntrinsicHeight object. '
         'This is relatively expensive, however.' // (that's why we don't do it automatically)
       );
-    });
+    }());
     final BoxConstraints innerConstraints = _getInnerConstraints(constraints);
     double position = 0.0;
     RenderBox child = firstChild;

packages/flutter/lib/src/rendering/box.dart

@@ -260,7 +260,7 @@ class BoxConstraints extends Constraints {
       if (size is _DebugSize)
         result = new _DebugSize(result, size._owner, size._canBeUsedByParent);
       return true;
-    });
+    }());
     return result;
   }
 
@@ -271,7 +271,7 @@ class BoxConstraints extends Constraints {
   /// separately provided widths and heights.
   Size constrain(Size size) {
     Size result = new Size(constrainWidth(size.width), constrainHeight(size.height));
-    assert(() { result = _debugPropagateDebugSize(size, result); return true; });
+    assert(() { result = _debugPropagateDebugSize(size, result); return true; }());
     return result;
   }
 
@@ -294,7 +294,7 @@ class BoxConstraints extends Constraints {
   Size constrainSizeAndAttemptToPreserveAspectRatio(Size size) {
     if (isTight) {
       Size result = smallest;
-      assert(() { result = _debugPropagateDebugSize(size, result); return true; });
+      assert(() { result = _debugPropagateDebugSize(size, result); return true; }());
       return result;
     }
 
@@ -325,7 +325,7 @@ class BoxConstraints extends Constraints {
     }
 
     Size result = new Size(constrainWidth(width), constrainHeight(height));
-    assert(() { result = _debugPropagateDebugSize(size, result); return true; });
+    assert(() { result = _debugPropagateDebugSize(size, result); return true; }());
     return result;
   }
 
@@ -495,7 +495,7 @@ class BoxConstraints extends Constraints {
       }
       assert(isNormalized);
       return true;
-    });
+    }());
     return isNormalized;
   }
 
@@ -1038,7 +1038,7 @@ abstract class RenderBox extends RenderObject {
       if (RenderObject.debugCheckingIntrinsics)
         shouldCache = false;
       return true;
-    });
+    }());
     if (shouldCache) {
       _cachedIntrinsicDimensions ??= <_IntrinsicDimensionsCacheEntry, double>{};
       return _cachedIntrinsicDimensions.putIfAbsent(
@@ -1085,7 +1085,7 @@ abstract class RenderBox extends RenderObject {
         );
       }
       return true;
-    });
+    }());
     return _computeIntrinsicDimension(_IntrinsicDimension.minWidth, height, computeMinIntrinsicWidth);
   }
 
@@ -1224,7 +1224,7 @@ abstract class RenderBox extends RenderObject {
         );
       }
       return true;
-    });
+    }());
     return _computeIntrinsicDimension(_IntrinsicDimension.maxWidth, height, computeMaxIntrinsicWidth);
   }
 
@@ -1300,7 +1300,7 @@ abstract class RenderBox extends RenderObject {
         );
       }
       return true;
-    });
+    }());
     return _computeIntrinsicDimension(_IntrinsicDimension.minHeight, width, computeMinIntrinsicHeight);
   }
 
@@ -1373,7 +1373,7 @@ abstract class RenderBox extends RenderObject {
         );
       }
       return true;
-    });
+    }());
     return _computeIntrinsicDimension(_IntrinsicDimension.maxHeight, width, computeMaxIntrinsicHeight);
   }
 
@@ -1443,7 +1443,7 @@ abstract class RenderBox extends RenderObject {
         assert(_size == this._size);
       }
       return true;
-    });
+    }());
     return _size;
   }
   Size _size;
@@ -1481,13 +1481,13 @@ abstract class RenderBox extends RenderObject {
         'The RenderBox in question is:\n'
         '  $this'
       );
-    });
+    }());
     assert(() {
       value = debugAdoptSize(value);
       return true;
-    });
+    }());
     _size = value;
-    assert(() { debugAssertDoesMeetConstraints(); return true; });
+    assert(() { debugAssertDoesMeetConstraints(); return true; }());
   }
 
   /// Claims ownership of the given [Size].
@@ -1549,7 +1549,7 @@ abstract class RenderBox extends RenderObject {
       }
       result = new _DebugSize(value, this, debugCanParentUseSize);
       return true;
-    });
+    }());
     return result;
   }
 
@@ -1594,7 +1594,7 @@ abstract class RenderBox extends RenderObject {
                ((RenderObject.debugActivePaint == this) && debugDoingThisPaint);
       assert(parent == this.parent);
       return false;
-    });
+    }());
     assert(_debugSetDoingBaseline(true));
     final double result = getDistanceToActualBaseline(baseline);
     assert(_debugSetDoingBaseline(false));
@@ -1752,7 +1752,7 @@ abstract class RenderBox extends RenderObject {
         }
       }
       return true;
-    });
+    }());
   }
 
   @override
@@ -1793,7 +1793,7 @@ abstract class RenderBox extends RenderObject {
         );
       }
       return true;
-    });
+    }());
   }
 
   /// Determines the set of render objects located at the given position.
@@ -1840,7 +1840,7 @@ abstract class RenderBox extends RenderObject {
         );
       }
       return true;
-    });
+    }());
     if (_size.contains(position)) {
       if (hitTestChildren(result, position: position) || hitTestSelf(position)) {
         result.add(new BoxHitTestEntry(this, position));
@@ -1901,7 +1901,7 @@ abstract class RenderBox extends RenderObject {
         );
       }
       return true;
-    });
+    }());
     final BoxParentData childParentData = child.parentData;
     final Offset offset = childParentData.offset;
     transform.translate(offset.dx, offset.dy);
@@ -2004,7 +2004,7 @@ abstract class RenderBox extends RenderObject {
         markNeedsPaint();
       }
       return true;
-    });
+    }());
     return true;
   }
 
@@ -2018,7 +2018,7 @@ abstract class RenderBox extends RenderObject {
       if (debugPaintPointersEnabled)
         debugPaintPointers(context, offset);
       return true;
-    });
+    }());
   }
 
   /// In debug mode, paints a border around this render box.
@@ -2033,7 +2033,7 @@ abstract class RenderBox extends RenderObject {
        ..color = const Color(0xFF00FFFF);
       context.canvas.drawRect((offset & size).deflate(0.5), paint);
       return true;
-    });
+    }());
   }
 
   /// In debug mode, paints a line for each baseline.
@@ -2065,7 +2065,7 @@ abstract class RenderBox extends RenderObject {
         context.canvas.drawPath(path, paint);
       }
       return true;
-    });
+    }());
   }
 
   /// In debug mode, paints a rectangle if this render box has counted more
@@ -2084,7 +2084,7 @@ abstract class RenderBox extends RenderObject {
         context.canvas.drawRect(offset & size, paint);
       }
       return true;
-    });
+    }());
   }
 
   @override

packages/flutter/lib/src/rendering/custom_layout.dart

@@ -120,7 +120,7 @@ abstract class MultiChildLayoutDelegate {
         );
       }
       return true;
-    });
+    }());
     child.layout(constraints, parentUsesSize: true);
     return child.size;
   }
@@ -146,7 +146,7 @@ abstract class MultiChildLayoutDelegate {
         );
       }
       return true;
-    });
+    }());
     final MultiChildLayoutParentData childParentData = child.parentData;
     childParentData.offset = offset;
   }
@@ -167,7 +167,7 @@ abstract class MultiChildLayoutDelegate {
       debugPreviousChildrenNeedingLayout = _debugChildrenNeedingLayout;
       _debugChildrenNeedingLayout = new Set<RenderBox>();
       return true;
-    });
+    }());
 
     try {
       _idToChild = <Object, RenderBox>{};
@@ -183,12 +183,12 @@ abstract class MultiChildLayoutDelegate {
             );
           }
           return true;
-        });
+        }());
         _idToChild[childParentData.id] = child;
         assert(() {
           _debugChildrenNeedingLayout.add(child);
           return true;
-        });
+        }());
         child = childParentData.nextSibling;
       }
       performLayout(size);
@@ -209,13 +209,13 @@ abstract class MultiChildLayoutDelegate {
           }
         }
         return true;
-      });
+      }());
     } finally {
       _idToChild = previousIdToChild;
       assert(() {
         _debugChildrenNeedingLayout = debugPreviousChildrenNeedingLayout;
         return true;
-      });
+      }());
     }
   }
 

packages/flutter/lib/src/rendering/debug.dart

@@ -203,7 +203,7 @@ void debugPaintPadding(Canvas canvas, Rect outerRect, Rect innerRect, { double o
       canvas.drawRect(outerRect, paint);
     }
     return true;
-  });
+  }());
 }
 
 /// Returns true if none of the rendering library debug variables have been changed.
@@ -234,6 +234,6 @@ bool debugAssertAllRenderVarsUnset(String reason, { bool debugCheckIntrinsicSize
       throw new FlutterError(reason);
     }
     return true;
-  });
+  }());
   return true;
 }

packages/flutter/lib/src/rendering/flex.dart

@@ -705,7 +705,7 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
             'If none of the above helps enough to fix this problem, please don\'t hesitate to file a bug:\n'
             '  https://github.com/flutter/flutter/issues/new'
           );
-        });
+        }());
         totalFlex += childParentData.flex;
       } else {
         BoxConstraints innerConstraints;
@@ -798,7 +798,7 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
             if (textBaseline == null)
               throw new FlutterError('To use FlexAlignItems.baseline, you must also specify which baseline to use using the "baseline" argument.');
             return true;
-          });
+          }());
           final double distance = child.getDistanceToBaseline(textBaseline, onlyReal: true);
           if (distance != null)
             maxBaselineDistance = math.max(maxBaselineDistance, distance);
@@ -1017,7 +1017,7 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
       }
 
       return true;
-    });
+    }());
   }
 
   @override

packages/flutter/lib/src/rendering/flow.dart

@@ -326,7 +326,7 @@ class RenderFlow extends RenderBox
         );
       }
       return true;
-    });
+    }());
     _lastPaintOrder.add(i);
     childParentData._transform = transform;
 

packages/flutter/lib/src/rendering/layer.dart

@@ -76,7 +76,7 @@ abstract class Layer extends AbstractNode with DiagnosticableTreeMixin {
         node = node.parent;
       assert(node != newLayer); // indicates we are about to create a cycle
       return true;
-    });
+    }());
     parent.adoptChild(newLayer);
     assert(newLayer.attached == parent.attached);
     if (parent.firstChild == this)
@@ -299,7 +299,7 @@ class ContainerLayer extends Layer {
         node = node.parent;
       assert(node != child); // indicates we are about to create a cycle
       return true;
-    });
+    }());
     adoptChild(child);
     child._previousSibling = lastChild;
     if (lastChild != null)

packages/flutter/lib/src/rendering/node.dart

@@ -122,7 +122,7 @@ class AbstractNode {
         node = node.parent;
       assert(node != child); // indicates we are about to create a cycle
       return true;
-    });
+    }());
     child._parent = this;
     if (attached)
       child.attach(_owner);

packages/flutter/lib/src/rendering/object.dart

@@ -101,7 +101,7 @@ class PaintingContext {
         includedChild: true,
       );
       return true;
-    });
+    }());
     if (child._layer == null) {
       assert(debugAlsoPaintedParent);
       child._layer = new OffsetLayer();
@@ -112,7 +112,7 @@ class PaintingContext {
     assert(() {
       child._layer.debugCreator = child.debugCreator ?? child.runtimeType;
       return true;
-    });
+    }());
     final PaintingContext childContext = new PaintingContext._(child._layer, child.paintBounds);
     child._paintWithContext(childContext, Offset.zero);
     childContext._stopRecordingIfNeeded();
@@ -128,7 +128,7 @@ class PaintingContext {
       if (debugProfilePaintsEnabled)
         Timeline.startSync('${child.runtimeType}', arguments: timelineWhitelistArguments);
       return true;
-    });
+    }());
 
     if (child.isRepaintBoundary) {
       _stopRecordingIfNeeded();
@@ -141,7 +141,7 @@ class PaintingContext {
       if (debugProfilePaintsEnabled)
         Timeline.finishSync();
       return true;
-    });
+    }());
   }
 
   void _compositeChild(RenderObject child, Offset offset) {
@@ -162,7 +162,7 @@ class PaintingContext {
         );
         child._layer.debugCreator = child.debugCreator ?? child;
         return true;
-      });
+      }());
     }
     child._layer.offset = offset;
     _appendLayer(child._layer);
@@ -187,7 +187,7 @@ class PaintingContext {
         assert(_canvas == null);
       }
       return true;
-    });
+    }());
     return hasCanvas;
   }
 
@@ -236,7 +236,7 @@ class PaintingContext {
         canvas.drawRect(canvasBounds, paint);
       }
       return true;
-    });
+    }());
     _currentLayer.picture = _recorder.endRecording();
     _currentLayer = null;
     _recorder = null;
@@ -633,7 +633,7 @@ abstract class _SemanticsFragment {
          for (_SemanticsFragment child in children)
            assert(seenChildren.add(child)); // check for duplicate adds
          return true;
-       }),
+       }()),
        _ancestorChain = <RenderObject>[renderObjectOwner],
        _children = children ?? const <_SemanticsFragment>[];
 
@@ -691,7 +691,7 @@ class _CleanSemanticsFragment extends _SemanticsFragment {
   @override
   Iterable<SemanticsNode> compile({ _SemanticsGeometry geometry, SemanticsNode currentSemantics, SemanticsNode parentSemantics }) sync* {
     assert(!_debugCompiled);
-    assert(() { _debugCompiled = true; return true; });
+    assert(() { _debugCompiled = true; return true; }());
     final SemanticsNode node = renderObjectOwner._semantics;
     assert(node != null);
     if (geometry != null) {
@@ -715,7 +715,7 @@ abstract class _InterestingSemanticsFragment extends _SemanticsFragment {
   @override
   Iterable<SemanticsNode> compile({ _SemanticsGeometry geometry, SemanticsNode currentSemantics, SemanticsNode parentSemantics }) sync* {
     assert(!_debugCompiled);
-    assert(() { _debugCompiled = true; return true; });
+    assert(() { _debugCompiled = true; return true; }());
     final SemanticsNode node = establishSemanticsNode(geometry, currentSemantics, parentSemantics);
     final List<SemanticsNode> children = <SemanticsNode>[];
     for (_SemanticsFragment child in _children) {
@@ -906,7 +906,7 @@ class _ForkingSemanticsFragment extends _SemanticsFragment {
     SemanticsNode parentSemantics
   }) sync* {
     assert(!_debugCompiled);
-    assert(() { _debugCompiled = true; return true; });
+    assert(() { _debugCompiled = true; return true; }());
     assert(geometry != null);
     geometry.applyAncestorChain(_ancestorChain);
     for (_SemanticsFragment child in _children) {
@@ -964,7 +964,7 @@ class SemanticsHandle {
         );
       }
       return true;
-    });
+    }());
     if (_owner != null) {
       if (listener != null)
         _owner.semanticsOwner.removeListener(listener);
@@ -1235,7 +1235,7 @@ class PipelineOwner {
       return;
     Timeline.startSync('Semantics');
     assert(_semanticsOwner != null);
-    assert(() { _debugDoingSemantics = true; return true; });
+    assert(() { _debugDoingSemantics = true; return true; }());
     try {
       final List<RenderObject> nodesToProcess = _nodesNeedingSemantics.toList()
         ..sort((RenderObject a, RenderObject b) => a.depth - b.depth);
@@ -1247,7 +1247,7 @@ class PipelineOwner {
       _semanticsOwner.sendSemanticsUpdate();
     } finally {
       assert(_nodesNeedingSemantics.isEmpty);
-      assert(() { _debugDoingSemantics = false; return true; });
+      assert(() { _debugDoingSemantics = false; return true; }());
       Timeline.finishSync();
     }
   }
@@ -1562,7 +1562,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         node = node.parent;
       }
       return true;
-    });
+    }());
     return result;
   }
 
@@ -1611,7 +1611,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     assert(() {
       result = _needsLayout;
       return true;
-    });
+    }());
     return result;
   }
   bool _needsLayout = true;
@@ -1710,7 +1710,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
           if (debugPrintMarkNeedsLayoutStacks)
             debugPrintStack(label: 'markNeedsLayout() called for $this');
           return true;
-        });
+        }());
         owner._nodesNeedingLayout.add(this);
         owner.requestVisualUpdate();
       }
@@ -1775,7 +1775,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     assert(() {
       _debugCanParentUseSize = false;
       return true;
-    });
+    }());
     owner._nodesNeedingLayout.add(this);
   }
 
@@ -1793,7 +1793,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       if (debugPrintLayouts)
         debugPrint('Laying out (without resize) $this');
       return true;
-    });
+    }());
     try {
       performLayout();
       markNeedsSemanticsUpdate();
@@ -1805,7 +1805,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       _debugDoingThisLayout = false;
       _debugMutationsLocked = false;
       return true;
-    });
+    }());
     _needsLayout = false;
     markNeedsPaint();
   }
@@ -1875,7 +1875,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     assert(() {
       _debugCanParentUseSize = parentUsesSize;
       return true;
-    });
+    }());
     if (!_needsLayout && constraints == _constraints && relayoutBoundary == _relayoutBoundary) {
       assert(() {
         // in case parentUsesSize changed since the last invocation, set size
@@ -1889,7 +1889,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         _debugDoingThisLayout = false;
         _debugDoingThisResize = false;
         return true;
-      });
+      }());
       return;
     }
     _constraints = constraints;
@@ -1901,16 +1901,16 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       if (debugPrintLayouts)
         debugPrint('Laying out (${sizedByParent ? "with separate resize" : "with resize allowed"}) $this');
       return true;
-    });
+    }());
     if (sizedByParent) {
-      assert(() { _debugDoingThisResize = true; return true; });
+      assert(() { _debugDoingThisResize = true; return true; }());
       try {
         performResize();
-        assert(() { debugAssertDoesMeetConstraints(); return true; });
+        assert(() { debugAssertDoesMeetConstraints(); return true; }());
       } catch (e, stack) {
         _debugReportException('performResize', e, stack);
       }
-      assert(() { _debugDoingThisResize = false; return true; });
+      assert(() { _debugDoingThisResize = false; return true; }());
     }
     RenderObject debugPreviousActiveLayout;
     assert(() {
@@ -1918,11 +1918,11 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       debugPreviousActiveLayout = _debugActiveLayout;
       _debugActiveLayout = this;
       return true;
-    });
+    }());
     try {
       performLayout();
       markNeedsSemanticsUpdate();
-      assert(() { debugAssertDoesMeetConstraints(); return true; });
+      assert(() { debugAssertDoesMeetConstraints(); return true; }());
     } catch (e, stack) {
       _debugReportException('performLayout', e, stack);
     }
@@ -1931,7 +1931,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       _debugDoingThisLayout = false;
       _debugMutationsLocked = false;
       return true;
-    });
+    }());
     _needsLayout = false;
     markNeedsPaint();
   }
@@ -2112,7 +2112,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     assert(() {
       result = _layer;
       return true;
-    });
+    }());
     return result;
   }
 
@@ -2147,7 +2147,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       if (parent is RenderObject)
         return parent._needsCompositing;
       return true;
-    });
+    }());
     // parent is fine (or there isn't one), but we are dirty
     if (owner != null)
       owner._nodesNeedingCompositingBitsUpdate.add(this);
@@ -2199,7 +2199,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     assert(() {
       result = _needsPaint;
       return true;
-    });
+    }());
     return result;
   }
   bool _needsPaint = true;
@@ -2228,7 +2228,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         if (debugPrintMarkNeedsPaintStacks)
           debugPrintStack(label: 'markNeedsPaint() called for $this');
         return true;
-      });
+      }());
       // If we always have our own layer, then we can just repaint
       // ourselves without involving any other nodes.
       assert(_layer != null);
@@ -2249,7 +2249,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         if (debugPrintMarkNeedsPaintStacks)
           debugPrintStack(label: 'markNeedsPaint() called for $this (root of render tree)');
         return true;
-      });
+      }());
       // If we're the root of the render tree (probably a RenderView),
       // then we have to paint ourselves, since nobody else can paint
       // us. We don't add ourselves to _nodesNeedingPaint in this
@@ -2332,7 +2332,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         );
       }
       return true;
-    });
+    }());
     // If we still need layout, then that means that we were skipped in the
     // layout phase and therefore don't need painting. We might not know that
     // yet (that is, our layer might not have been detached yet), because the
@@ -2357,7 +2357,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         );
       }
       return true;
-    });
+    }());
     RenderObject debugLastActivePaint;
     assert(() {
       _debugDoingThisPaint = true;
@@ -2365,7 +2365,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       _debugActivePaint = this;
       assert(!isRepaintBoundary || _layer != null);
       return true;
-    });
+    }());
     _needsPaint = false;
     try {
       paint(context, offset);
@@ -2379,7 +2379,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       _debugActivePaint = debugLastActivePaint;
       _debugDoingThisPaint = false;
       return true;
-    });
+    }());
   }
 
   /// The bounds within which this render object will paint.
@@ -2534,7 +2534,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     assert(() {
       result = _semantics;
       return true;
-    });
+    }());
     return result;
   }
 
@@ -2947,7 +2947,7 @@ abstract class RenderObjectWithChildMixin<ChildType extends RenderObject> extend
         );
       }
       return true;
-    });
+    }());
     return true;
   }
 
@@ -3084,7 +3084,7 @@ abstract class ContainerRenderObjectMixin<ChildType extends RenderObject, Parent
         );
       }
       return true;
-    });
+    }());
     return true;
   }
 

packages/flutter/lib/src/rendering/paragraph.dart

@@ -331,7 +331,7 @@ class RenderParagraph extends RenderBox {
         canvas.drawRect(offset & size, paint);
       }
       return true;
-    });
+    }());
 
     if (_hasVisualOverflow) {
       final Rect bounds = offset & size;

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -272,7 +272,7 @@ class RenderConstrainedBox extends RenderProxyBox {
         context.canvas.drawRect(offset & size, paint);
       }
       return true;
-    });
+    }());
   }
 
   @override
@@ -463,7 +463,7 @@ class RenderAspectRatio extends RenderProxyBox {
         );
       }
       return true;
-    });
+    }());
 
     if (constraints.isTight)
       return constraints.smallest;
@@ -1043,7 +1043,7 @@ abstract class _RenderCustomClip<T> extends RenderProxyBox {
         )
         ..layout();
       return true;
-    });
+    }());
   }
 }
 
@@ -1093,7 +1093,7 @@ class RenderClipRect extends _RenderCustomClip<Rect> {
         _debugText.paint(context.canvas, offset + new Offset(_clip.width / 8.0, -_debugText.text.style.fontSize * 1.1));
       }
       return true;
-    });
+    }());
   }
 }
 
@@ -1164,7 +1164,7 @@ class RenderClipRRect extends _RenderCustomClip<RRect> {
         _debugText.paint(context.canvas, offset + new Offset(_clip.tlRadiusX, -_debugText.text.style.fontSize * 1.1));
       }
       return true;
-    });
+    }());
   }
 }
 
@@ -1228,7 +1228,7 @@ class RenderClipOval extends _RenderCustomClip<Rect> {
         _debugText.paint(context.canvas, offset + new Offset((_clip.width - _debugText.width) / 2.0, -_debugText.text.style.fontSize * 1.1));
       }
       return true;
-    });
+    }());
   }
 }
 
@@ -1286,7 +1286,7 @@ class RenderClipPath extends _RenderCustomClip<Path> {
         _debugText.paint(context.canvas, offset);
       }
       return true;
-    });
+    }());
   }
 }
 
@@ -1555,7 +1555,7 @@ class RenderDecoratedBox extends RenderProxyBox {
       assert(() {
         debugSaveCount = context.canvas.getSaveCount();
         return true;
-      });
+      }());
       _painter.paint(context.canvas, offset, filledConfiguration);
       assert(() {
         if (debugSaveCount != context.canvas.getSaveCount()) {
@@ -1571,7 +1571,7 @@ class RenderDecoratedBox extends RenderProxyBox {
           );
         }
         return true;
-      });
+      }());
       if (decoration.isComplex)
         context.setIsComplexHint();
     }
@@ -2294,7 +2294,7 @@ class RenderCustomPaint extends RenderProxyBox {
   void _paintWithPainter(Canvas canvas, Offset offset, CustomPainter painter) {
     int debugPreviousCanvasSaveCount;
     canvas.save();
-    assert(() { debugPreviousCanvasSaveCount = canvas.getSaveCount(); return true; });
+    assert(() { debugPreviousCanvasSaveCount = canvas.getSaveCount(); return true; }());
     if (offset != Offset.zero)
       canvas.translate(offset.dx, offset.dy);
     painter.paint(canvas, size);
@@ -2328,7 +2328,7 @@ class RenderCustomPaint extends RenderProxyBox {
         );
       }
       return debugNewCanvasSaveCount == debugPreviousCanvasSaveCount;
-    });
+    }());
     canvas.restore();
   }
 
@@ -2513,7 +2513,7 @@ class RenderRepaintBoundary extends RenderProxyBox {
       _debugSymmetricPaintCount = 0;
       _debugAsymmetricPaintCount = 0;
       return true;
-    });
+    }());
   }
 
   @override
@@ -2524,7 +2524,7 @@ class RenderRepaintBoundary extends RenderProxyBox {
       else
         _debugAsymmetricPaintCount += 1;
       return true;
-    });
+    }());
   }
 
   @override
@@ -2557,7 +2557,7 @@ class RenderRepaintBoundary extends RenderProxyBox {
         description.add(new MessageProperty('diagnosis', diagnosis));
       }
       return true;
-    });
+    }());
     if (inReleaseMode)
       description.add(new DiagnosticsNode.message('(run in checked mode to collect repaint boundary statistics)'));
   }

packages/flutter/lib/src/rendering/semantics.dart

@@ -467,13 +467,13 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
         ancestor = ancestor.parent;
       assert(!_newChildren.any((SemanticsNode child) => child == ancestor));
       return true;
-    });
+    }());
     assert(() {
       final Set<SemanticsNode> seenChildren = new Set<SemanticsNode>();
       for (SemanticsNode child in _newChildren)
         assert(seenChildren.add(child)); // check for duplicate adds
       return true;
-    });
+    }());
   }
 
   /// Contains the children in inverse hit test order (i.e. paint order).

packages/flutter/lib/src/rendering/shifted_box.dart

@@ -202,7 +202,7 @@ class RenderPadding extends RenderShiftedBox {
       final Rect outerRect = offset & size;
       debugPaintPadding(context.canvas, outerRect, child != null ? _resolvedPadding.deflateRect(outerRect) : null);
       return true;
-    });
+    }());
   }
 
   @override
@@ -422,7 +422,7 @@ class RenderPositionedBox extends RenderAligningShiftedBox {
         context.canvas.drawRect(offset & size, paint);
       }
       return true;
-    });
+    }());
   }
 
   @override

packages/flutter/lib/src/rendering/sliver.dart

@@ -453,7 +453,7 @@ class SliverConstraints extends Constraints {
       verify(remainingPaintExtent >= 0.0, 'The "remainingPaintExtent" is negative.');
       verify(isNormalized, 'The constraints are not normalized.'); // should be redundant with earlier checks
       return true;
-    });
+    }());
     return true;
   }
 
@@ -669,7 +669,7 @@ class SliverGeometry extends Diagnosticable {
       verify(hasVisualOverflow != null, 'The "hasVisualOverflow" is null.');
       verify(scrollOffsetCorrection != 0.0, 'The "scrollOffsetCorrection" is zero.');
       return true;
-    });
+    }());
     return true;
   }
 
@@ -991,7 +991,7 @@ abstract class RenderSliver extends RenderObject {
         'The RenderSliver in question is:\n'
         '  $this'
       );
-    });
+    }());
     _geometry = value;
   }
 
@@ -1042,7 +1042,7 @@ abstract class RenderSliver extends RenderObject {
         );
       }
       return true;
-    });
+    }());
   }
 
   @override
@@ -1195,7 +1195,7 @@ abstract class RenderSliver extends RenderObject {
   double childMainAxisPosition(covariant RenderObject child) {
     assert(() {
       throw new FlutterError('$runtimeType does not implement childPosition.');
-    });
+    }());
     return 0.0;
   }
 
@@ -1232,7 +1232,7 @@ abstract class RenderSliver extends RenderObject {
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(() {
       throw new FlutterError('$runtimeType does not implement applyPaintTransform.');
-    });
+    }());
   }
 
   /// This returns a [Size] with dimensions relative to the leading edge of the
@@ -1291,7 +1291,7 @@ abstract class RenderSliver extends RenderObject {
         paint
       );
       return true;
-    });
+    }());
   }
 
   @override
@@ -1358,7 +1358,7 @@ abstract class RenderSliver extends RenderObject {
         }
       }
       return true;
-    });
+    }());
   }
 
   // This override exists only to change the type of the second argument.

packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart

@@ -201,7 +201,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
         child = childAfter(child);
       }
       return true;
-    });
+    }());
   }
 
   @override
@@ -567,7 +567,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
         child = childAfter(child);
       }
       return true;
-    });
+    }());
     return true;
   }
 

packages/flutter/lib/src/rendering/sliver_padding.dart

@@ -302,7 +302,7 @@ class RenderSliverPadding extends RenderSliver with RenderObjectWithChildMixin<R
         debugPaintPadding(context.canvas, outerRect, innerRect);
       }
       return true;
-    });
+    }());
   }
 
   @override

packages/flutter/lib/src/rendering/sliver_persistent_header.dart

@@ -138,7 +138,7 @@ abstract class RenderSliverPersistentHeader extends RenderSliver with RenderObje
         'The specified maxExtent was: ${maxExtent.toStringAsFixed(1)}\n'
         'The specified minExtent was: ${minExtent.toStringAsFixed(1)}\n'
       );
-    });
+    }());
     child?.layout(
       constraints.asBoxConstraints(maxExtent: math.max(minExtent, maxExtent - shrinkOffset)),
       parentUsesSize: true,

packages/flutter/lib/src/rendering/table.dart

@@ -882,7 +882,7 @@ class RenderTable extends RenderBox {
     }
 
     // beyond this point, unflexedTableWidth is no longer valid
-    assert(() { unflexedTableWidth = null; return true; });
+    assert(() { unflexedTableWidth = null; return true; }());
 
     // 4. apply the maximum width of the table, shrinking columns as
     //    necessary, applying minimum column widths as we go

packages/flutter/lib/src/rendering/view.dart

@@ -195,7 +195,7 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
         if (debugRepaintRainbowEnabled || debugRepaintTextRainbowEnabled)
           debugCurrentRepaintColor = debugCurrentRepaintColor.withHue(debugCurrentRepaintColor.hue + 2.0);
         return true;
-      });
+      }());
     } finally {
       Timeline.finishSync();
     }
@@ -218,7 +218,7 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
     assert(() {
       description.add(new DiagnosticsNode.message('debug mode enabled - ${Platform.operatingSystem}'));
       return true;
-    });
+    }());
     description.add(new DiagnosticsProperty<Size>('window size', ui.window.physicalSize, tooltip: 'in physical pixels'));
     description.add(new DoubleProperty('device pixel ratio', ui.window.devicePixelRatio, tooltip: 'physical pixels per logical pixel'));
     description.add(new DiagnosticsProperty<ViewConfiguration>('configuration', configuration, tooltip: 'in logical pixels'));

packages/flutter/lib/src/rendering/viewport.dart

@@ -201,7 +201,7 @@ abstract class RenderViewportBase<ParentDataClass extends ContainerParentDataMix
         );
       }
       return true;
-    });
+    }());
     return true;
   }
 
@@ -296,7 +296,7 @@ abstract class RenderViewportBase<ParentDataClass extends ContainerParentDataMix
       ), parentUsesSize: true);
 
       final SliverGeometry childLayoutGeometry = child.geometry;
-      assert(childLayoutGeometry.debugAssertIsValid);
+      assert(childLayoutGeometry.debugAssertIsValid());
 
       // If there is a correction to apply, we'll have to start over.
       if (childLayoutGeometry.scrollOffsetCorrection != null)
@@ -366,7 +366,7 @@ abstract class RenderViewportBase<ParentDataClass extends ContainerParentDataMix
         child = childAfter(child);
       }
       return true;
-    });
+    }());
   }
 
   @override
@@ -848,7 +848,7 @@ class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentDat
         }
       }
       return true;
-    });
+    }());
     size = constraints.biggest;
     // We ignore the return value of applyViewportDimension below because we are
     // going to go through performLayout next regardless.
@@ -935,7 +935,7 @@ class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentDat
         );
       }
       return true;
-    });
+    }());
   }
 
   double _attemptLayout(double mainAxisExtent, double crossAxisExtent, double correctedOffset) {
@@ -1217,7 +1217,7 @@ class RenderShrinkWrappingViewport extends RenderViewportBase<SliverLogicalConta
         );
       }
       return true;
-    });
+    }());
     return true;
   }
 

packages/flutter/lib/src/scheduler/binding.dart

@@ -73,14 +73,14 @@ class _FrameCallbackEntry {
             );
           }
           return true;
-        });
+        }());
         debugStack = debugCurrentCallbackStack;
       } else {
         // TODO(ianh): trim the frames from this library, so that the call to scheduleFrameCallback is the top one
         debugStack = StackTrace.current;
       }
       return true;
-    });
+    }());
   }
 
   final FrameCallback callback;
@@ -363,7 +363,7 @@ abstract class SchedulerBinding extends BindingBase {
         ));
       }
       return true;
-    });
+    }());
     return true;
   }
 
@@ -399,7 +399,7 @@ abstract class SchedulerBinding extends BindingBase {
         debugPrint('No transient callback is currently executing.');
       }
       return true;
-    });
+    }());
   }
 
   final List<FrameCallback> _persistentCallbacks = <FrameCallback>[];
@@ -503,7 +503,7 @@ abstract class SchedulerBinding extends BindingBase {
       if (debugPrintScheduleFrameStacks)
         debugPrintStack(label: 'scheduleFrame() called. Current phase is $schedulerPhase.');
       return true;
-    });
+    }());
     ui.window.scheduleFrame();
     _hasScheduledFrame = true;
   }
@@ -610,7 +610,7 @@ abstract class SchedulerBinding extends BindingBase {
           debugPrint(_debugBanner);
       }
       return true;
-    });
+    }());
 
     assert(schedulerPhase == SchedulerPhase.idle);
     _hasScheduledFrame = false;
@@ -667,7 +667,7 @@ abstract class SchedulerBinding extends BindingBase {
           debugPrint('▀' * _debugBanner.length);
         _debugBanner = null;
         return true;
-      });
+      }());
       _currentFrameTimeStamp = null;
     }
 
@@ -708,7 +708,7 @@ abstract class SchedulerBinding extends BindingBase {
     assert(callback != null);
     assert(_FrameCallbackEntry.debugCurrentCallbackStack == null);
     // TODO(ianh): Consider using a Zone instead to track the current callback registration stack
-    assert(() { _FrameCallbackEntry.debugCurrentCallbackStack = callbackStack; return true; });
+    assert(() { _FrameCallbackEntry.debugCurrentCallbackStack = callbackStack; return true; }());
     try {
       callback(timeStamp);
     } catch (exception, exceptionStack) {
@@ -727,7 +727,7 @@ abstract class SchedulerBinding extends BindingBase {
         }
       ));
     }
-    assert(() { _FrameCallbackEntry.debugCurrentCallbackStack = null; return true; });
+    assert(() { _FrameCallbackEntry.debugCurrentCallbackStack = null; return true; }());
   }
 }
 

packages/flutter/lib/src/scheduler/debug.dart

@@ -64,6 +64,6 @@ bool debugAssertAllSchedulerVarsUnset(String reason) {
       throw new FlutterError(reason);
     }
     return true;
-  });
+  }());
   return true;
 }

packages/flutter/lib/src/scheduler/ticker.dart

@@ -63,7 +63,7 @@ class Ticker {
     assert(() {
       _debugCreationStack = StackTrace.current;
       return true;
-    });
+    }());
   }
 
   TickerFuture _future;
@@ -140,7 +140,7 @@ class Ticker {
         );
       }
       return true;
-    });
+    }());
     assert(_startTime == null);
     _future = new TickerFuture._();
     if (shouldScheduleTick)
@@ -290,7 +290,7 @@ class Ticker {
       // catch cases of use-after-dispose.
       _startTime = const Duration();
       return true;
-    });
+    }());
   }
 
   /// An optional label can be provided for debugging purposes.
@@ -306,7 +306,7 @@ class Ticker {
     assert(() {
       buffer.write(debugLabel ?? '');
       return true;
-    });
+    }());
     buffer.write(')');
     assert(() {
       if (debugIncludeStack) {
@@ -315,7 +315,7 @@ class Ticker {
         FlutterError.defaultStackFilter(_debugCreationStack.toString().trimRight().split('\n')).forEach(buffer.writeln);
       }
       return true;
-    });
+    }());
     return buffer.toString();
   }
 }

packages/flutter/lib/src/widgets/app.dart

@@ -486,7 +486,7 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
         );
       }
       return true;
-    });
+    }());
 
     return new MediaQuery(
       data: new MediaQueryData.fromWindow(ui.window),

packages/flutter/lib/src/widgets/automatic_keep_alive.dart

@@ -113,7 +113,7 @@ class _AutomaticKeepAliveState extends State<AutomaticKeepAlive> {
           );
         }
         return true;
-      });
+      }());
       _handles.remove(handle);
       if (_handles.isEmpty) {
         if (SchedulerBinding.instance.schedulerPhase.index < SchedulerPhase.persistentCallbacks.index) {

packages/flutter/lib/src/widgets/banner.dart

@@ -343,7 +343,7 @@ class CheckedModeBanner extends StatelessWidget {
         location: BannerLocation.topEnd,
       );
       return true;
-    });
+    }());
     return result;
   }
 
@@ -354,7 +354,7 @@ class CheckedModeBanner extends StatelessWidget {
     assert(() {
       message = '"SLOW MODE"';
       return true;
-    });
+    }());
     description.add(new DiagnosticsNode.message(message));
   }
 }

packages/flutter/lib/src/widgets/binding.dart

@@ -441,7 +441,7 @@ abstract class WidgetsBinding extends BindingBase with GestureBinding, RendererB
         );
       }
       return true;
-    });
+    }());
     ensureVisualUpdate();
   }
 
@@ -524,7 +524,7 @@ abstract class WidgetsBinding extends BindingBase with GestureBinding, RendererB
     assert(() {
       debugBuildingDirtyElements = true;
       return true;
-    });
+    }());
     try {
       if (renderViewElement != null)
         buildOwner.buildScope(renderViewElement);
@@ -534,7 +534,7 @@ abstract class WidgetsBinding extends BindingBase with GestureBinding, RendererB
       assert(() {
         debugBuildingDirtyElements = false;
         return true;
-      });
+      }());
     }
     // TODO(ianh): Following code should not be included in release mode, only profile and debug modes.
     // See https://github.com/dart-lang/sdk/issues/27192
@@ -613,7 +613,7 @@ void runApp(Widget app) {
 void debugDumpApp() {
   assert(WidgetsBinding.instance != null);
   String mode = 'RELEASE MODE';
-  assert(() { mode = 'CHECKED MODE'; return true; });
+  assert(() { mode = 'CHECKED MODE'; return true; }());
   debugPrint('${WidgetsBinding.instance.runtimeType} - $mode');
   if (WidgetsBinding.instance.renderViewElement != null) {
     debugPrint(WidgetsBinding.instance.renderViewElement.toStringDeep());

packages/flutter/lib/src/widgets/debug.dart

@@ -113,7 +113,7 @@ bool debugChildrenHaveDuplicateKeys(Widget parent, Iterable<Widget> children) {
       );
     }
     return true;
-  });
+  }());
   return false;
 }
 
@@ -135,7 +135,7 @@ bool debugItemsHaveDuplicateKeys(Iterable<Widget> items) {
     if (nonUniqueKey != null)
       throw new FlutterError('Duplicate key found: $nonUniqueKey.');
     return true;
-  });
+  }());
   return false;
 }
 
@@ -165,7 +165,7 @@ bool debugCheckHasTable(BuildContext context) {
       );
     }
     return true;
-  });
+  }());
   return true;
 }
 
@@ -198,7 +198,7 @@ bool debugCheckHasMediaQuery(BuildContext context) {
       );
     }
     return true;
-  });
+  }());
   return true;
 }
 
@@ -220,7 +220,7 @@ void debugWidgetBuilderValue(Widget widget, Widget built) {
       );
     }
     return true;
-  });
+  }());
 }
 
 /// Returns true if none of the widget library debug variables have been changed.
@@ -241,6 +241,6 @@ bool debugAssertAllWidgetVarsUnset(String reason) {
       throw new FlutterError(reason);
     }
     return true;
-  });
+  }());
   return true;
 }

packages/flutter/lib/src/widgets/dismissible.dart

@@ -388,7 +388,7 @@ class _DismissibleState extends State<Dismissible> with TickerProviderStateMixin
           );
         }
         return true;
-      });
+      }());
 
       return new SizeTransition(
         sizeFactor: _resizeAnimation,

packages/flutter/lib/src/widgets/focus_manager.dart

@@ -158,7 +158,7 @@ class FocusScopeNode extends Object with DiagnosticableTreeMixin {
         node = node._parent;
       assert(node != child); // indicates we are about to create a cycle
       return true;
-    });
+    }());
     child._parent = this;
     child._nextSibling = _firstChild;
     if (_firstChild != null)

packages/flutter/lib/src/widgets/framework.dart

@@ -197,7 +197,7 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
         _debugIllFatedElements.add(_registry[this]);
       }
       return true;
-    });
+    }());
     _registry[this] = element;
   }
 
@@ -209,7 +209,7 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
         assert(element.widget.runtimeType != _registry[this].widget.runtimeType);
       }
       return true;
-    });
+    }());
     if (_registry[this] == element) {
       _registry.remove(this);
       _removedKeys.add(this);
@@ -246,7 +246,7 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
       }
       _debugReservations[this] = parent;
       return true;
-    });
+    }());
   }
 
   static void _debugVerifyIllFatedPopulation() {
@@ -280,7 +280,7 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
         throw new FlutterError(buffer.toString());
       }
       return true;
-    });
+    }());
   }
 
   Element get _currentElement => _registry[this];
@@ -1158,7 +1158,7 @@ abstract class State<T extends StatefulWidget> extends Diagnosticable {
         );
       }
       return true;
-    });
+    }());
     final dynamic result = fn() as dynamic;
     assert(() {
       if (result is Future) {
@@ -1174,7 +1174,7 @@ abstract class State<T extends StatefulWidget> extends Diagnosticable {
       // We ignore other types of return values so that you can do things like:
       //   setState(() => x = 3);
       return true;
-    });
+    }());
     _element.markNeedsBuild();
   }
 
@@ -1230,7 +1230,7 @@ abstract class State<T extends StatefulWidget> extends Diagnosticable {
   @mustCallSuper
   void dispose() {
     assert(_debugLifecycleState == _StateLifecycle.ready);
-    assert(() { _debugLifecycleState = _StateLifecycle.defunct; return true; });
+    assert(() { _debugLifecycleState = _StateLifecycle.defunct; return true; }());
   }
 
   /// Describes the part of the user interface represented by this widget.
@@ -1374,7 +1374,7 @@ abstract class State<T extends StatefulWidget> extends Diagnosticable {
     assert(() {
       description.add(new EnumProperty<_StateLifecycle>('lifecycle state', _debugLifecycleState, defaultValue: _StateLifecycle.ready));
       return true;
-    });
+    }());
     description.add(new ObjectFlagProperty<T>('_widget', _widget, ifNull: 'no widget'));
     description.add(new ObjectFlagProperty<StatefulElement>('_element', _element, ifNull: 'not mounted'));
   }
@@ -1737,7 +1737,7 @@ class _InactiveElements {
           debugPrint('Discarding $element from inactive elements list.');
       }
       return true;
-    });
+    }());
     element.visitChildren((Element child) {
       assert(child._parent == element);
       _unmount(child);
@@ -1764,7 +1764,7 @@ class _InactiveElements {
     element.deactivate();
     assert(element._debugLifecycleState == _ElementLifecycle.inactive);
     element.visitChildren(_deactivateRecursively);
-    assert(() { element.debugDeactivated(); return true; });
+    assert(() { element.debugDeactivated(); return true; }());
   }
 
   void add(Element element) {
@@ -1789,7 +1789,7 @@ class _InactiveElements {
     assert(() {
       result = _elements.contains(element);
       return true;
-    });
+    }());
     return result;
   }
 }
@@ -2128,7 +2128,7 @@ class BuildOwner {
         );
       }
       return true;
-    });
+    }());
     if (element._inDirtyList) {
       assert(() {
         if (debugPrintScheduleBuildForStacks)
@@ -2141,7 +2141,7 @@ class BuildOwner {
           );
         }
         return true;
-      });
+      }());
       _dirtyElementsNeedsResorting = true;
       return;
     }
@@ -2155,7 +2155,7 @@ class BuildOwner {
       if (debugPrintScheduleBuildForStacks)
         debugPrint('...dirty list is now: $_dirtyElements');
       return true;
-    });
+    }());
   }
 
   int _debugStateLockLevel = 0;
@@ -2174,14 +2174,14 @@ class BuildOwner {
     assert(() {
       _debugStateLockLevel += 1;
       return true;
-    });
+    }());
     try {
       callback();
     } finally {
       assert(() {
         _debugStateLockLevel -= 1;
         return true;
-      });
+      }());
     }
     assert(_debugStateLockLevel >= 0);
   }
@@ -2223,7 +2223,7 @@ class BuildOwner {
       _debugStateLockLevel += 1;
       _debugBuilding = true;
       return true;
-    });
+    }());
     Timeline.startSync('Build', arguments: timelineWhitelistArguments);
     try {
       _scheduledFlushDirtyElements = true;
@@ -2235,7 +2235,7 @@ class BuildOwner {
           debugPreviousBuildTarget = _debugCurrentBuildTarget;
           _debugCurrentBuildTarget = context;
          return true;
-        });
+        }());
         _dirtyElementsNeedsResorting = false;
         try {
           callback();
@@ -2246,7 +2246,7 @@ class BuildOwner {
             _debugCurrentBuildTarget = debugPreviousBuildTarget;
             _debugElementWasRebuilt(context);
             return true;
-          });
+          }());
         }
       }
       _dirtyElements.sort(Element._sort);
@@ -2295,7 +2295,7 @@ class BuildOwner {
           );
         }
         return true;
-      });
+      }());
     } finally {
       for (Element element in _dirtyElements) {
         assert(element._inDirtyList);
@@ -2312,7 +2312,7 @@ class BuildOwner {
         if (debugPrintBuildScope)
           debugPrint('buildScope finished');
         return true;
-      });
+      }());
     }
     assert(_debugStateLockLevel >= 0);
   }
@@ -2423,7 +2423,7 @@ class BuildOwner {
           _debugElementsThatWillNeedToBeRebuiltDueToGlobalKeyShenanigans?.clear();
         }
         return true;
-      });
+      }());
     } catch (e, stack) {
       _debugReportException('while finalizing the widget tree', e, stack);
     } finally {
@@ -2631,7 +2631,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
         'so the children might not be constructed yet, or might be old children '
         'that are going to be replaced.'
       );
-    });
+    }());
     visitChildren(visitor);
   }
 
@@ -2674,7 +2674,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
         key._debugReserveFor(this);
       }
       return true;
-    });
+    }());
     if (newWidget == null) {
       if (child != null)
         deactivateChild(child);
@@ -2694,7 +2694,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
         assert(() {
           child.owner._debugElementWasRebuilt(child);
           return true;
-        });
+        }());
         return child;
       }
       deactivateChild(child);
@@ -2732,7 +2732,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
       key._register(this);
     }
     _updateInheritance();
-    assert(() { _debugLifecycleState = _ElementLifecycle.active; return true; });
+    assert(() { _debugLifecycleState = _ElementLifecycle.active; return true; }());
   }
 
   /// Change the widget used to configure this element.
@@ -2838,7 +2838,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
       if (debugPrintGlobalKeyedWidgetLifecycle)
         debugPrint('Attempting to take $element from ${element._parent ?? "inactive elements list"} to put in $this.');
       return true;
-    });
+    }());
     final Element parent = element._parent;
     if (parent != null) {
       assert(() {
@@ -2857,7 +2857,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
           key,
         );
         return true;
-      });
+      }());
       parent.forgetChild(element);
       parent.deactivateChild(element);
     }
@@ -2888,7 +2888,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
       final Element newChild = _retakeInactiveElement(key, newWidget);
       if (newChild != null) {
         assert(newChild._parent == null);
-        assert(() { _debugCheckForCycles(newChild); return true; });
+        assert(() { _debugCheckForCycles(newChild); return true; }());
         newChild._activateWithParent(this, newSlot);
         final Element updatedChild = updateChild(newChild, newWidget, newSlot);
         assert(newChild == updatedChild);
@@ -2896,7 +2896,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
       }
     }
     final Element newChild = newWidget.createElement();
-    assert(() { _debugCheckForCycles(newChild); return true; });
+    assert(() { _debugCheckForCycles(newChild); return true; }());
     newChild.mount(this, newSlot);
     assert(newChild._debugLifecycleState == _ElementLifecycle.active);
     return newChild;
@@ -2910,7 +2910,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
         node = node._parent;
       assert(node != newChild); // indicates we are about to create a cycle
       return true;
-    });
+    }());
   }
 
   /// Move the given element to the list of inactive elements and detach its
@@ -2940,7 +2940,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
           debugPrint('Deactivated $child (keyed child of $this)');
       }
       return true;
-    });
+    }());
   }
 
   /// Remove the given child from the element's child list, in preparation for
@@ -2961,7 +2961,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
       if (debugPrintGlobalKeyedWidgetLifecycle)
         debugPrint('Reactivating $this (now child of $_parent).');
       return true;
-    });
+    }());
     _updateDepth(_parent.depth);
     _activateRecursively(this);
     attachRenderObject(newSlot);
@@ -2997,7 +2997,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
     _dependencies?.clear();
     _hadUnsatisfiedDependencies = false;
     _updateInheritance();
-    assert(() { _debugLifecycleState = _ElementLifecycle.active; return true; });
+    assert(() { _debugLifecycleState = _ElementLifecycle.active; return true; }());
     if (_dirty)
       owner.scheduleBuildFor(this);
     if (hadDependencies)
@@ -3034,7 +3034,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
     }
     _inheritedWidgets = null;
     _active = false;
-    assert(() { _debugLifecycleState = _ElementLifecycle.inactive; return true; });
+    assert(() { _debugLifecycleState = _ElementLifecycle.inactive; return true; }());
   }
 
   /// Called, in debug mode, after children have been deactivated (see [deactivate]).
@@ -3066,7 +3066,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
       final GlobalKey key = widget.key;
       key._unregister(this);
     }
-    assert(() { _debugLifecycleState = _ElementLifecycle.defunct; return true; });
+    assert(() { _debugLifecycleState = _ElementLifecycle.defunct; return true; }());
   }
 
   @override
@@ -3105,7 +3105,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
         );
       }
       return true;
-    });
+    }());
     final RenderObject renderObject = findRenderObject();
     assert(() {
       if (renderObject == null) {
@@ -3180,7 +3180,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
         );
       }
       return true;
-    });
+    }());
     if (renderObject is RenderBox)
       return renderObject.size;
     return null;
@@ -3202,13 +3202,13 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
         );
       }
       return true;
-    });
+    }());
     return true;
   }
 
   @override
   InheritedWidget inheritFromWidgetOfExactType(Type targetType) {
-    assert(_debugCheckStateIsActiveForAncestorLoopkup);
+    assert(_debugCheckStateIsActiveForAncestorLoopkup());
     final InheritedElement ancestor = _inheritedWidgets == null ? null : _inheritedWidgets[targetType];
     if (ancestor != null) {
       assert(ancestor is InheritedElement);
@@ -3223,7 +3223,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
 
   @override
   InheritedElement ancestorInheritedElementForWidgetOfExactType(Type targetType) {
-    assert(_debugCheckStateIsActiveForAncestorLoopkup);
+    assert(_debugCheckStateIsActiveForAncestorLoopkup());
     final InheritedElement ancestor = _inheritedWidgets == null ? null : _inheritedWidgets[targetType];
     return ancestor;
   }
@@ -3235,7 +3235,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
 
   @override
   Widget ancestorWidgetOfExactType(Type targetType) {
-    assert(_debugCheckStateIsActiveForAncestorLoopkup);
+    assert(_debugCheckStateIsActiveForAncestorLoopkup());
     Element ancestor = _parent;
     while (ancestor != null && ancestor.widget.runtimeType != targetType)
       ancestor = ancestor._parent;
@@ -3244,7 +3244,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
 
   @override
   State ancestorStateOfType(TypeMatcher matcher) {
-    assert(_debugCheckStateIsActiveForAncestorLoopkup);
+    assert(_debugCheckStateIsActiveForAncestorLoopkup());
     Element ancestor = _parent;
     while (ancestor != null) {
       if (ancestor is StatefulElement && matcher.check(ancestor.state))
@@ -3257,7 +3257,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
 
   @override
   RenderObject ancestorRenderObjectOfType(TypeMatcher matcher) {
-    assert(_debugCheckStateIsActiveForAncestorLoopkup);
+    assert(_debugCheckStateIsActiveForAncestorLoopkup());
     Element ancestor = _parent;
     while (ancestor != null) {
       if (ancestor is RenderObjectElement && matcher.check(ancestor.renderObject))
@@ -3270,7 +3270,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
 
   @override
   void visitAncestorElements(bool visitor(Element element)) {
-    assert(_debugCheckStateIsActiveForAncestorLoopkup);
+    assert(_debugCheckStateIsActiveForAncestorLoopkup());
     Element ancestor = _parent;
     while (ancestor != null && visitor(ancestor))
       ancestor = ancestor._parent;
@@ -3421,7 +3421,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
         );
       }
       return true;
-    });
+    }());
     if (dirty)
       return;
     _dirty = true;
@@ -3445,7 +3445,7 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
         }
       }
       return true;
-    });
+    }());
     assert(_debugLifecycleState == _ElementLifecycle.active);
     assert(owner._debugStateLocked);
     Element debugPreviousBuildTarget;
@@ -3453,13 +3453,13 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
       debugPreviousBuildTarget = owner._debugCurrentBuildTarget;
       owner._debugCurrentBuildTarget = this;
       return true;
-    });
+    }());
     performRebuild();
     assert(() {
       assert(owner._debugCurrentBuildTarget == this);
       owner._debugCurrentBuildTarget = debugPreviousBuildTarget;
       return true;
-    });
+    }());
     assert(!_dirty);
   }
 
@@ -3548,7 +3548,7 @@ abstract class ComponentElement extends Element {
       if (debugProfileBuildsEnabled)
         Timeline.startSync('${widget.runtimeType}');
       return true;
-    });
+    }());
 
     assert(_debugSetAllowIgnoredCallsToMarkNeedsBuild(true));
     Widget built;
@@ -3577,7 +3577,7 @@ abstract class ComponentElement extends Element {
       if (debugProfileBuildsEnabled)
         Timeline.finishSync();
       return true;
-    });
+    }());
   }
 
   /// Subclasses should override this function to actually call the appropriate
@@ -3634,7 +3634,7 @@ class StatefulElement extends ComponentElement {
         );
       }
       return true;
-    });
+    }());
     assert(_state._element == null);
     _state._element = this;
     assert(_state._widget == null);
@@ -3668,9 +3668,9 @@ class StatefulElement extends ComponentElement {
     } finally {
       _debugSetAllowIgnoredCallsToMarkNeedsBuild(false);
     }
-    assert(() { _state._debugLifecycleState = _StateLifecycle.initialized; return true; });
+    assert(() { _state._debugLifecycleState = _StateLifecycle.initialized; return true; }());
     _state.didChangeDependencies();
-    assert(() { _state._debugLifecycleState = _StateLifecycle.ready; return true; });
+    assert(() { _state._debugLifecycleState = _StateLifecycle.ready; return true; }());
     super._firstBuild();
   }
 
@@ -3721,7 +3721,7 @@ class StatefulElement extends ComponentElement {
         'dispose() implementations must always call their superclass dispose() method, to ensure '
         'that all the resources used by the widget are fully released.'
       );
-    });
+    }());
     _state._element = null;
     _state = null;
   }
@@ -3763,7 +3763,7 @@ class StatefulElement extends ComponentElement {
         );
       }
       return true;
-    });
+    }());
     return super.inheritFromWidgetOfExactType(targetType);
   }
 
@@ -3845,7 +3845,7 @@ class ParentDataElement<T extends RenderObjectWidget> extends ProxyElement {
           badAncestors: badAncestors
         )
       );
-    });
+    }());
     super.mount(parent, slot);
   }
 
@@ -3932,7 +3932,7 @@ class InheritedElement extends ProxyElement {
     assert(() {
       assert(_dependents.isEmpty);
       return true;
-    });
+    }());
     super.debugDeactivated();
   }
 
@@ -3959,7 +3959,7 @@ class InheritedElement extends ProxyElement {
         while (ancestor != this && ancestor != null)
           ancestor = ancestor._parent;
         return ancestor == this;
-      });
+      }());
       // check that it really deepends on us
       assert(dependent._dependencies.contains(this));
       dependent.didChangeDependencies();
@@ -4168,7 +4168,7 @@ abstract class RenderObjectElement extends Element {
   void mount(Element parent, dynamic newSlot) {
     super.mount(parent, newSlot);
     _renderObject = widget.createRenderObject(this);
-    assert(() { _debugUpdateRenderObjectOwner(); return true; });
+    assert(() { _debugUpdateRenderObjectOwner(); return true; }());
     assert(_slot == newSlot);
     attachRenderObject(newSlot);
     _dirty = false;
@@ -4178,7 +4178,7 @@ abstract class RenderObjectElement extends Element {
   void update(covariant RenderObjectWidget newWidget) {
     super.update(newWidget);
     assert(widget == newWidget);
-    assert(() { _debugUpdateRenderObjectOwner(); return true; });
+    assert(() { _debugUpdateRenderObjectOwner(); return true; }());
     widget.updateRenderObject(this, renderObject);
     _dirty = false;
   }
@@ -4187,7 +4187,7 @@ abstract class RenderObjectElement extends Element {
     assert(() {
       _renderObject.debugCreator = new _DebugCreator(this);
       return true;
-    });
+    }());
   }
 
   @override

packages/flutter/lib/src/widgets/gesture_detector.dart

@@ -185,7 +185,7 @@ class GestureDetector extends StatelessWidget {
            }
          }
          return true;
-       }),
+       }()),
        super(key: key);
 
   /// The widget below this widget in the tree.
@@ -524,7 +524,7 @@ class RawGestureDetectorState extends State<RawGestureDetector> {
         );
       }
       return true;
-    });
+    }());
     _syncAll(gestures);
     if (!widget.excludeFromSemantics) {
       final RenderSemanticsGestureHandler semanticsGestureHandler = context.findRenderObject();
@@ -554,7 +554,7 @@ class RawGestureDetectorState extends State<RawGestureDetector> {
         );
       }
       return true;
-    });
+    }());
     if (!widget.excludeFromSemantics) {
       final RenderSemanticsGestureHandler semanticsGestureHandler = context.findRenderObject();
       semanticsGestureHandler.validActions = actions;

packages/flutter/lib/src/widgets/heroes.dart

@@ -121,7 +121,7 @@ class Hero extends StatefulWidget {
             );
           }
           return true;
-        });
+        }());
         final _HeroState heroState = hero.state;
         result[tag] = heroState;
       }
@@ -310,7 +310,7 @@ class _HeroFlight {
         case _HeroFlightType.push:
           return initial.value == 0.0 && initial.status == AnimationStatus.forward;
       }
-    });
+    }());
 
     manifest = initialManifest;
 

packages/flutter/lib/src/widgets/layout_builder.dart

@@ -173,7 +173,7 @@ class _RenderLayoutBuilder extends RenderBox with RenderObjectWithChildMixin<Ren
         );
       }
       return true;
-    });
+    }());
     return true;
   }
 

packages/flutter/lib/src/widgets/navigator.dart

@@ -718,7 +718,7 @@ class Navigator extends StatefulWidget {
         );
       }
       return true;
-    });
+    }());
     return navigator;
   }
 
@@ -779,7 +779,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
             ),
           );
           return true;
-        });
+        }());
         push(_routeNamed(Navigator.defaultRouteName));
       } else {
         for (Route<dynamic> route in plannedInitialRoutes)
@@ -813,7 +813,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
   @override
   void dispose() {
     assert(!_debugLocked);
-    assert(() { _debugLocked = true; return true; });
+    assert(() { _debugLocked = true; return true; }());
     for (NavigatorObserver observer in widget.observers)
       observer._navigator = null;
     final List<Route<dynamic>> doomed = _poppedRoutes.toList()..addAll(_history);
@@ -823,7 +823,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
     _history.clear();
     focusScopeNode.detach();
     super.dispose();
-    assert(() { _debugLocked = false; return true; });
+    assert(() { _debugLocked = false; return true; }());
   }
 
   /// The overlay this navigator uses for its visual presentation.
@@ -859,7 +859,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
           );
         }
         return true;
-      });
+      }());
       route = widget.onUnknownRoute(settings);
       assert(() {
         if (route == null) {
@@ -872,7 +872,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
           );
         }
         return true;
-      });
+      }());
     }
     return route;
   }
@@ -908,7 +908,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
   /// when the pushed route is popped off the navigator.
   Future<dynamic> push(Route<dynamic> route) {
     assert(!_debugLocked);
-    assert(() { _debugLocked = true; return true; });
+    assert(() { _debugLocked = true; return true; }());
     assert(route != null);
     assert(route._navigator == null);
     setState(() {
@@ -923,7 +923,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
       for (NavigatorObserver observer in widget.observers)
         observer.didPush(route, oldRoute);
     });
-    assert(() { _debugLocked = false; return true; });
+    assert(() { _debugLocked = false; return true; }());
     _cancelActivePointers();
     return route.popped;
   }
@@ -942,7 +942,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
     assert(newRoute != null);
     if (oldRoute == newRoute)
       return;
-    assert(() { _debugLocked = true; return true; });
+    assert(() { _debugLocked = true; return true; }());
     assert(oldRoute._navigator == this);
     assert(newRoute._navigator == null);
     assert(oldRoute.overlayEntries.isNotEmpty);
@@ -965,7 +965,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
         _history[index - 1].didChangeNext(newRoute);
       oldRoute.dispose();
     });
-    assert(() { _debugLocked = false; return true; });
+    assert(() { _debugLocked = false; return true; }());
   }
 
   /// Push the [newRoute] and dispose the old current Route.
@@ -980,7 +980,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
   /// as if the old route had been popped.
   Future<dynamic> pushReplacement(Route<dynamic> newRoute, { dynamic result }) {
     assert(!_debugLocked);
-    assert(() { _debugLocked = true; return true; });
+    assert(() { _debugLocked = true; return true; }());
     final Route<dynamic> oldRoute = _history.last;
     assert(oldRoute != null && oldRoute._navigator == this);
     assert(oldRoute.overlayEntries.isNotEmpty);
@@ -1008,7 +1008,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
       for (NavigatorObserver observer in widget.observers)
         observer.didPush(newRoute, oldRoute);
     });
-    assert(() { _debugLocked = false; return true; });
+    assert(() { _debugLocked = false; return true; }());
     _cancelActivePointers();
     return newRoute.popped;
   }
@@ -1047,7 +1047,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
   /// [Route.didChangePrevious]). The navigator observer is not notified.
   void removeRouteBelow(Route<dynamic> anchorRoute) {
     assert(!_debugLocked);
-    assert(() { _debugLocked = true; return true; });
+    assert(() { _debugLocked = true; return true; }());
     assert(anchorRoute._navigator == this);
     final int index = _history.indexOf(anchorRoute) - 1;
     assert(index >= 0);
@@ -1064,7 +1064,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
         nextRoute.didChangePrevious(previousRoute);
       targetRoute.dispose();
     });
-    assert(() { _debugLocked = false; return true; });
+    assert(() { _debugLocked = false; return true; }());
   }
 
   /// Push the given route and then remove all the previous routes until the
@@ -1080,7 +1080,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
   /// that always returns false.
   Future<dynamic> pushAndRemoveUntil(Route<dynamic> newRoute, RoutePredicate predicate) {
     assert(!_debugLocked);
-    assert(() { _debugLocked = true; return true; });
+    assert(() { _debugLocked = true; return true; }());
     final List<Route<dynamic>> removedRoutes = <Route<dynamic>>[];
     while (_history.isNotEmpty && !predicate(_history.last)) {
       final Route<dynamic> removedRoute = _history.removeLast();
@@ -1107,7 +1107,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
       for (NavigatorObserver observer in widget.observers)
         observer.didPush(newRoute, oldRoute);
     });
-    assert(() { _debugLocked = false; return true; });
+    assert(() { _debugLocked = false; return true; }());
     _cancelActivePointers();
     return newRoute.popped;
   }
@@ -1167,11 +1167,11 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
   /// popped.
   bool pop([dynamic result]) {
     assert(!_debugLocked);
-    assert(() { _debugLocked = true; return true; });
+    assert(() { _debugLocked = true; return true; }());
     final Route<dynamic> route = _history.last;
     assert(route._navigator == this);
     bool debugPredictedWouldPop;
-    assert(() { debugPredictedWouldPop = !route.willHandlePopInternally; return true; });
+    assert(() { debugPredictedWouldPop = !route.willHandlePopInternally; return true; }());
     if (route.didPop(result ?? route.currentResult)) {
       assert(debugPredictedWouldPop);
       if (_history.length > 1) {
@@ -1190,13 +1190,13 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
             observer.didPop(route, _history.last);
         });
       } else {
-        assert(() { _debugLocked = false; return true; });
+        assert(() { _debugLocked = false; return true; }());
         return false;
       }
     } else {
       assert(!debugPredictedWouldPop);
     }
-    assert(() { _debugLocked = false; return true; });
+    assert(() { _debugLocked = false; return true; }());
     _cancelActivePointers();
     return true;
   }
@@ -1213,7 +1213,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
   void removeRoute(Route<dynamic> route) {
     assert(route != null);
     assert(!_debugLocked);
-    assert(() { _debugLocked = true; return true; });
+    assert(() { _debugLocked = true; return true; }());
     assert(route._navigator == this);
     final int index = _history.indexOf(route);
     assert(index != -1);
@@ -1227,7 +1227,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
         observer.didRemove(route, previousRoute);
       route.dispose();
     });
-    assert(() { _debugLocked = false; return true; });
+    assert(() { _debugLocked = false; return true; }());
     _cancelActivePointers();
   }
 

packages/flutter/lib/src/widgets/overlay.dart

@@ -251,7 +251,7 @@ class Overlay extends StatefulWidget {
         );
       }
       return true;
-    });
+    }());
     return result;
   }
 
@@ -331,7 +331,7 @@ class OverlayState extends State<Overlay> with TickerProviderStateMixin {
           break;
       }
       return true;
-    });
+    }());
     return result;
   }
 

packages/flutter/lib/src/widgets/scroll_physics.dart

@@ -369,7 +369,7 @@ class ClampingScrollPhysics extends ScrollPhysics {
         );
       }
       return true;
-    });
+    }());
     if (value < position.pixels && position.pixels <= position.minScrollExtent) // underscroll
       return value - position.pixels;
     if (position.maxScrollExtent <= position.pixels && position.pixels < value) // overscroll

packages/flutter/lib/src/widgets/scroll_position.dart

@@ -209,7 +209,7 @@ abstract class ScrollPosition extends ViewportOffset with ScrollMetrics {
           );
         }
         return true;
-      });
+      }());
       final double oldPixels = _pixels;
       _pixels = newPixels - overscroll;
       if (_pixels != oldPixels) {
@@ -351,7 +351,7 @@ abstract class ScrollPosition extends ViewportOffset with ScrollMetrics {
         );
       }
       return true;
-    });
+    }());
     return result;
   }
 

packages/flutter/lib/src/widgets/sliver.dart

@@ -842,7 +842,7 @@ class SliverMultiBoxAdaptorElement extends RenderObjectElement implements Render
       final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
       assert(slot == childParentData.index);
       return true;
-    });
+    }());
   }
 
   @override

packages/flutter/lib/src/widgets/table.dart

@@ -111,7 +111,7 @@ class Table extends RenderObjectWidget {
            );
          }
          return true;
-       }),
+       }()),
        assert(() {
          if (children.any((TableRow row1) => row1.key != null && children.any((TableRow row2) => row1 != row2 && row1.key == row2.key))) {
            throw new FlutterError(
@@ -120,7 +120,7 @@ class Table extends RenderObjectWidget {
            );
          }
          return true;
-       }),
+       }()),
        assert(() {
          if (children.isNotEmpty) {
            final int cellCount = children.first.children.length;
@@ -133,7 +133,7 @@ class Table extends RenderObjectWidget {
            }
          }
          return true;
-       }),
+       }()),
        _rowDecorations = children.any((TableRow row) => row.decoration != null)
                               ? children.map<Decoration>((TableRow row) => row.decoration).toList(growable: false)
                               : null,
@@ -149,7 +149,7 @@ class Table extends RenderObjectWidget {
         );
       }
       return true;
-    });
+    }());
   }
 
   /// The rows of the table.
@@ -243,7 +243,7 @@ class _TableElement extends RenderObjectElement {
   void mount(Element parent, dynamic newSlot) {
     super.mount(parent, newSlot);
     assert(!_debugWillReattachChildren);
-    assert(() { _debugWillReattachChildren = true; return true; });
+    assert(() { _debugWillReattachChildren = true; return true; }());
     _children = widget.children.map((TableRow row) {
       return new _TableElementRow(
         key: row.key,
@@ -253,7 +253,7 @@ class _TableElement extends RenderObjectElement {
         }).toList(growable: false)
       );
     }).toList(growable: false);
-    assert(() { _debugWillReattachChildren = false; return true; });
+    assert(() { _debugWillReattachChildren = false; return true; }());
     _updateRenderObjectChildren();
   }
 
@@ -278,7 +278,7 @@ class _TableElement extends RenderObjectElement {
           return true;
       }
       return false;
-    });
+    }());
     final TableCellParentData childParentData = child.parentData;
     renderObject.setChild(childParentData.x, childParentData.y, null);
   }
@@ -288,7 +288,7 @@ class _TableElement extends RenderObjectElement {
   @override
   void update(Table newWidget) {
     assert(!_debugWillReattachChildren);
-    assert(() { _debugWillReattachChildren = true; return true; });
+    assert(() { _debugWillReattachChildren = true; return true; }());
     final Map<LocalKey, List<Element>> oldKeyedRows = new Map<LocalKey, List<Element>>.fromIterable(
       _children.where((_TableElementRow row) => row.key != null),
       key:   (_TableElementRow row) => row.key,
@@ -316,7 +316,7 @@ class _TableElement extends RenderObjectElement {
       updateChildren(oldUnkeyedRows.current.children, const <Widget>[], forgottenChildren: _forgottenChildren);
     for (List<Element> oldChildren in oldKeyedRows.values.where((List<Element> list) => !taken.contains(list)))
       updateChildren(oldChildren, const <Widget>[], forgottenChildren: _forgottenChildren);
-    assert(() { _debugWillReattachChildren = false; return true; });
+    assert(() { _debugWillReattachChildren = false; return true; }());
     _children = newChildren;
     _updateRenderObjectChildren();
     _forgottenChildren.clear();

packages/flutter/lib/src/widgets/ticker_provider.dart

@@ -92,7 +92,7 @@ abstract class SingleTickerProviderStateMixin extends State<dynamic> implements
         'objects and those objects might use it more than one time in total, then instead of '
         'mixing in a SingleTickerProviderStateMixin, use a regular TickerProviderStateMixin.'
       );
-    });
+    }());
     _ticker = new Ticker(onTick, debugLabel: 'created by $this');
     // We assume that this is called from initState, build, or some sort of
     // event handler, and that thus TickerMode.of(context) would return true. We
@@ -115,7 +115,7 @@ abstract class SingleTickerProviderStateMixin extends State<dynamic> implements
         'Otherwise, the ticker will leak.\n'
         'The offending ticker was: ${_ticker.toString(debugIncludeStack: true)}'
       );
-    });
+    }());
     super.dispose();
   }
 
@@ -195,7 +195,7 @@ abstract class TickerProviderStateMixin extends State<dynamic> implements Ticker
         }
       }
       return true;
-    });
+    }());
     super.dispose();
   }
 

packages/flutter/lib/src/widgets/widget_inspector.dart

@@ -406,7 +406,7 @@ class _InspectorOverlayLayer extends Layer {
     assert(() {
       inDebugMode = true;
       return true;
-    });
+    }());
     if (inDebugMode == false) {
       throw new FlutterError(
         'The inspector should never be used in production mode due to the '

packages/flutter_test/lib/src/widget_tester.dart

@@ -115,7 +115,7 @@ Future<Null> benchmarkWidgets(WidgetTesterCallback callback) {
     print('│                                                        ');
     print('└─────────────────────────────────────────────────╌┄┈  🐢');
     return true;
-  });
+  }());
   final TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized();
   assert(binding is! AutomatedTestWidgetsFlutterBinding);
   final WidgetTester tester = new WidgetTester._(binding);