fix #26812, function types should support the call method

[email protected]

Review URL: https://codereview.chromium.org/2226903003 .

Author: John Messerly

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

@@ -643,7 +643,9 @@ class ElementResolver extends SimpleAstVisitor<Object> {
         }
         staticElement = _resolveElement(typeReference, methodName);
       } else {
-        DartType staticType = _getStaticType(target);
+        DartType staticType = _resolver.strongMode
+            ? _getStaticTypeOrFunctionType(target)
+            : _getStaticType(target);
         DartType propagatedType = _getPropagatedType(target);
         staticElement = _resolveInvokedElementWithTarget(
             target, staticType, methodName, isConditional);
@@ -1544,10 +1546,7 @@ class ElementResolver extends SimpleAstVisitor<Object> {
    * type analysis.
    */
   DartType _getStaticType(Expression expression) {
-    if (expression is NullLiteral) {
-      return _resolver.typeProvider.bottomType;
-    }
-    DartType staticType = _resolveTypeParameter(expression.staticType);
+    DartType staticType = _getStaticTypeOrFunctionType(expression);
     if (staticType is FunctionType) {
       //
       // All function types are subtypes of 'Function', which is itself a
@@ -1558,6 +1557,13 @@ class ElementResolver extends SimpleAstVisitor<Object> {
     return staticType;
   }
 
+  DartType _getStaticTypeOrFunctionType(Expression expression) {
+    if (expression is NullLiteral) {
+      return _resolver.typeProvider.bottomType;
+    }
+    return _resolveTypeParameter(expression.staticType);
+  }
+
   /**
    * Check for a generic method & apply type arguments if any were passed.
    */
@@ -2224,6 +2230,10 @@ class ElementResolver extends SimpleAstVisitor<Object> {
       return element;
     } else if (target is SimpleIdentifier) {
       Element targetElement = target.staticElement;
+      if (targetType is FunctionType &&
+          methodName.name == FunctionElement.CALL_METHOD_NAME) {
+        return targetElement;
+      }
       if (targetElement is PrefixElement) {
         if (isConditional) {
           _resolver.errorReporter.reportErrorForNode(

pkg/analyzer/test/src/task/strong/checker_test.dart

@@ -113,6 +113,15 @@ test() {
 ''');
   }
 
+  void test_callMethodOnFunctions() {
+    checkFile(r'''
+void f(int x) => print(x);
+main() {
+  f.call(/*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/'hi');
+}
+    ''');
+  }
+
   void test_castsInConditions() {
     checkFile('''
 main() {