Flow analysis: change tryPromoteToNonNull to promoteToNonNull.

stereotype441 · commit-bot@chromium.org · commit b912aebf5ced · 2019-07-22T15:58:48.000Z
The flow analysis engine is now responsible for figuring out whether a promotion actually occurred; this is less error prone. Change-Id: Idce8af01fae982a9cc240ec4675812f8d7fd68a0 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/109883 Commit-Queue: Paul Berry <paulberry@google.com> Reviewed-by: Johnni Winther <johnniwinther@google.com> Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
diff --git a/pkg/analyzer/lib/src/dart/resolver/flow_analysis.dart b/pkg/analyzer/lib/src/dart/resolver/flow_analysis.dart
@@ -684,9 +684,9 @@ class State<Variable, Type> {
       TypeOperations<Variable, Type> typeOperations, Variable variable) {
     var previousType = promoted[variable];
     previousType ??= typeOperations.variableType(variable);
-    var type = typeOperations.tryPromoteToNonNull(previousType);
+    var type = typeOperations.promoteToNonNull(previousType);
 
-    if (type != null) {
+    if (!typeOperations.isSameType(type, previousType)) {
       var newPromoted = <Variable, Type>{}..addAll(promoted);
       newPromoted[variable] = type;
       return State<Variable, Type>._(
@@ -924,12 +924,11 @@ abstract class TypeOperations<Variable, Type> {
   /// Return `true` if the [leftType] is a subtype of the [rightType].
   bool isSubtypeOf(Type leftType, Type rightType);
 
-  /// Returns the non-null promoted version of [type], if it is different,
-  /// otherwise `null`.  For example, given `int?`, returns `int`.
+  /// Returns the non-null promoted version of [type].
   ///
   /// Note that some types don't have a non-nullable version (e.g.
-  /// `FutureOr<int?>`), so `null` may be returned even if the type is nullable.
-  Type tryPromoteToNonNull(Type type);
+  /// `FutureOr<int?>`), so [type] may be returned even if it is nullable.
+  Type /*!*/ promoteToNonNull(Type type);
 
   /// Return the static type of the given [variable].
   Type variableType(Variable variable);
diff --git a/pkg/analyzer/lib/src/dart/resolver/flow_analysis_visitor.dart b/pkg/analyzer/lib/src/dart/resolver/flow_analysis_visitor.dart
@@ -479,9 +479,8 @@ class _TypeSystemTypeOperations
   }
 
   @override
-  DartType tryPromoteToNonNull(covariant TypeImpl type) {
-    TypeImpl promotedType = typeSystem.promoteToNonNull(type);
-    return isSameType(type, promotedType) ? null : promotedType;
+  DartType promoteToNonNull(DartType type) {
+    return typeSystem.promoteToNonNull(type);
   }
 
   @override
diff --git a/pkg/analyzer/test/src/dart/resolution/flow_analysis_unit_test.dart b/pkg/analyzer/test/src/dart/resolution/flow_analysis_unit_test.dart
@@ -500,11 +500,12 @@ class _Harness
   }
 
   @override
-  _Type tryPromoteToNonNull(_Type type) {
+  _Type promoteToNonNull(_Type type) {
     if (type.type.endsWith('?')) {
       return _Type(type.type.substring(0, type.type.length - 1));
+    } else {
+      return type;
     }
-    return null;
   }
 
   @override
diff --git a/pkg/nnbd_migration/lib/src/decorated_type_operations.dart b/pkg/nnbd_migration/lib/src/decorated_type_operations.dart
@@ -32,7 +32,7 @@ class DecoratedTypeOperations
   }
 
   @override
-  DecoratedType tryPromoteToNonNull(DecoratedType type) {
+  DecoratedType promoteToNonNull(DecoratedType type) {
     throw new UnimplementedError('TODO(paulberry)');
   }
 

Original file line number	Diff line number	Diff line change
`@@ -479,9 +479,8 @@ class _TypeSystemTypeOperations`
`479`	`479`	`}`
`480`	`480`
`481`	`481`	`@override`
`482`		`- DartType tryPromoteToNonNull(covariant TypeImpl type) {`
`483`		`- TypeImpl promotedType = typeSystem.promoteToNonNull(type);`
`484`		`- return isSameType(type, promotedType) ? null : promotedType;`
	`482`	`+ DartType promoteToNonNull(DartType type) {`
	`483`	`+ return typeSystem.promoteToNonNull(type);`
`485`	`484`	`}`
`486`	`485`
`487`	`486`	`@override`
Original file line number	Diff line number	Diff line change
`@@ -500,11 +500,12 @@ class _Harness`
`500`	`500`	`}`
`501`	`501`
`502`	`502`	`@override`
`503`		`- _Type tryPromoteToNonNull(_Type type) {`
	`503`	`+ _Type promoteToNonNull(_Type type) {`
`504`	`504`	`if (type.type.endsWith('?')) {`
`505`	`505`	`return _Type(type.type.substring(0, type.type.length - 1));`
	`506`	`+ } else {`
	`507`	`+ return type;`
`506`	`508`	`}`
`507`		`- return null;`
`508`	`509`	`}`
`509`	`510`
`510`	`511`	`@override`
Original file line number	Diff line number	Diff line change
`@@ -32,7 +32,7 @@ class DecoratedTypeOperations`
`32`	`32`	`}`
`33`	`33`
`34`	`34`	`@override`
`35`		`- DecoratedType tryPromoteToNonNull(DecoratedType type) {`
	`35`	`+ DecoratedType promoteToNonNull(DecoratedType type) {`
`36`	`36`	`throw new UnimplementedError('TODO(paulberry)');`
`37`	`37`	`}`
`38`	`38`