Type inference for StringConcatenation.

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

 // Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
 import 'package:front_end/src/base/instrumentation.dart';
 import 'package:front_end/src/fasta/type_inference/type_inference_engine.dart';
 import 'package:front_end/src/fasta/type_inference/type_promotion.dart';
 import 'package:front_end/src/fasta/type_inference/type_schema_environment.dart';
 import 'package:kernel/ast.dart'
     show DartType, DynamicType, InterfaceType, Member;
@@ skipping 225 matching lines @@
   }
 
   /// 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
+  /// [inferExpression].
+  DartType inferStringConcatenation(
+      DartType typeContext, bool typeNeeded, Iterable<E> expressions) {
+    for (E expression in expressions) {
+      inferExpression(expression, null, false);
+    }
+    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
   /// should be inferred.  [initializer] is the initializer expression.
   /// [offset] is the character offset of the variable declaration (for
   /// instrumentation).  [setType] is a callback that will be used to set the
   /// inferred type.
   void inferVariableDeclaration(DartType declaredType, E initializer,
       int offset, void setType(DartType type)) {
     if (initializer == null) return;
@@ skipping 45 matching lines @@
   /// Gets the return type that was inferred for the current closure.
   get inferredReturnType {
     if (_inferredReturnType == null) {
       // No return statement found.
       // TODO(paulberry): is it correct to infer `dynamic`?
       return const DynamicType();
     }
     return _inferredReturnType;
   }
 }