Infer VariableSet types.

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

Index: pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
diff --git a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
index 182b654675acfd59052ba63c887e1564608f5eb4..91ea0e06d0b7cb2cf3a87112ba03688a7dde4505 100644
--- a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
@@ -249,14 +249,6 @@ abstract class TypeInferrerImpl<S, E, V, F> extends TypeInferrer<S, E, V, F> {
     return typeNeeded ? getterType : null;
   }
 
-  /// Performs the core type inference algorithm for string literals.
-  ///
-  /// [typeContext], [typeNeeded], and the return value behave as described in
-  /// [inferExpression].
-  DartType inferStringLiteral(DartType typeContext, bool typeNeeded) {
-    return typeNeeded ? coreTypes.stringClass.rawType : null;
-  }
-
   /// Performs the core type inference algorithm for string concatenations.
   ///
   /// [typeContext], [typeNeeded], and the return value behave as described in
@@ -269,6 +261,14 @@ abstract class TypeInferrerImpl<S, E, V, F> extends TypeInferrer<S, E, V, F> {
     return typeNeeded ? coreTypes.stringClass.rawType : null;
   }
 
+  /// Performs the core type inference algorithm for string literals.
+  ///
+  /// [typeContext], [typeNeeded], and the return value behave as described in
+  /// [inferExpression].
+  DartType inferStringLiteral(DartType typeContext, bool typeNeeded) {
+    return typeNeeded ? coreTypes.stringClass.rawType : null;
+  }
+
   /// Performs the core type inference algorithm for variable declarations.
   ///
   /// [declaredType] is the declared type of the variable, or `null` if the type
@@ -311,6 +311,11 @@ abstract class TypeInferrerImpl<S, E, V, F> extends TypeInferrer<S, E, V, F> {
         ? (promotedType ?? declaredType ?? const DynamicType())
         : null;
   }
+
+  DartType inferVariableSet(bool typeNeeded, DartType declaredType, E value) {
+    var valueType = inferExpression(value, declaredType, typeNeeded);
+    return typeNeeded ? valueType : null;

[Paul Berry, 2017/05/04 19:31:03]

This seems unnecessary to me.  The convention is that all of the infer...()
functions always return `null` if `typeNeeded` is `false`, so we should be able
to just do:

return valueType;

[scheglov, 2017/05/04 19:41:01]

Done.

+  }
 }
 
 /// Keeps track of information about the innermost function or closure being