Start work on a non-complete type inferrer. Currently only analyzes return types.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

Index: sdk/lib/_internal/compiler/implementation/resolution/members.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/resolution/members.dart	(revision 18311)
+++ sdk/lib/_internal/compiler/implementation/resolution/members.dart	(working copy)
@@ -1837,6 +1837,9 @@
     FunctionElement function = new FunctionElementX.node(
         name, node, ElementKind.FUNCTION, Modifiers.EMPTY,
         enclosingElement);
+    // [function] and its enclosing method share the same
+    // [TreeElementMapping].
+    compiler.enqueuer.resolution.resolvedElements[function] = mapping;
     Scope oldScope = scope; // The scope is modified by [setupFunction].
     setupFunction(node, function);
     defineElement(node, function, doAddToScope: node.name != null);