fixes #25477, downward inference of generic methods

pkg/analyzer/lib/src/generated/resolver.dart

 // Copyright (c) 2014, 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 file.
 
 library analyzer.src.generated.resolver;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 8144 matching lines @@
       _enclosingFunction = outerFunction;
     }
     return null;
   }
 
   @override
   Object visitFunctionExpressionInvocation(FunctionExpressionInvocation node) {
     safelyVisit(node.function);
     node.accept(elementResolver);
     _inferFunctionExpressionsParametersTypes(node.argumentList);
-    InferenceContext.setType(node.argumentList, node.function.staticType);
+    _inferArgumentTypesFromContext(node);
     safelyVisit(node.argumentList);
     node.accept(typeAnalyzer);
     return null;
   }
 
   @override
   Object visitFunctionTypeAlias(FunctionTypeAlias node) {
     // Resolve the metadata in the library scope.
     if (node.metadata != null) {
       node.metadata.accept(this);
@@ skipping 198 matching lines @@
   @override
   Object visitMethodInvocation(MethodInvocation node) {
     //
     // We visit the target and argument list, but do not visit the method name
     // because it needs to be visited in the context of the invocation.
     //
     safelyVisit(node.target);
     safelyVisit(node.typeArguments);
     node.accept(elementResolver);
     _inferFunctionExpressionsParametersTypes(node.argumentList);
-    DartType contextType = node.staticInvokeType;
-    if (contextType is FunctionType) {
-      InferenceContext.setType(node.argumentList, contextType);
-    }
+    _inferArgumentTypesFromContext(node);
     safelyVisit(node.argumentList);
     node.accept(typeAnalyzer);
     return null;
   }
 
+  void _inferArgumentTypesFromContext(InvocationExpression node) {
+    DartType contextType = node.staticInvokeType;
+    if (contextType is FunctionType) {
+      DartType originalType = node.function.staticType;
+      DartType returnContextType = InferenceContext.getType(node);
+      TypeSystem ts = typeSystem;
+      if (returnContextType != null &&
+          node.typeArguments == null &&
+          originalType is FunctionType &&
+          originalType.typeFormals.isNotEmpty &&
+          ts is StrongTypeSystemImpl) {
+
+        contextType = ts.inferGenericFunctionCall(typeProvider, originalType,
+            DartType.EMPTY_LIST, DartType.EMPTY_LIST, returnContextType);
+      }
+
+      InferenceContext.setType(node.argumentList, contextType);
+    }
+  }
+
   @override
   Object visitNamedExpression(NamedExpression node) {
     InferenceContext.setType(node.expression, InferenceContext.getType(node));
     return super.visitNamedExpression(node);
   }
 
   @override
   Object visitNode(AstNode node) {
     node.visitChildren(this);
     node.accept(elementResolver);
@@ skipping 4380 matching lines @@
     nonFields.add(node);
     return null;
   }
 
   @override
   Object visitNode(AstNode node) => node.accept(TypeResolverVisitor_this);
 
   @override
   Object visitWithClause(WithClause node) => null;
 }