Fix for issue 12569

editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java

Index: editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java
diff --git a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java
index c5e8549d1e2ea764295e5bb8a5606c046c38d861..3043a795c9fe276218e4b94b49f55ed702f78b3d 100644
--- a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java
+++ b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java
@@ -49,6 +49,7 @@ import com.google.dart.engine.ast.FormalParameterList;
 import com.google.dart.engine.ast.FunctionBody;
 import com.google.dart.engine.ast.FunctionDeclaration;
 import com.google.dart.engine.ast.FunctionExpression;
+import com.google.dart.engine.ast.FunctionExpressionInvocation;
 import com.google.dart.engine.ast.FunctionTypeAlias;
 import com.google.dart.engine.ast.FunctionTypedFormalParameter;
 import com.google.dart.engine.ast.Identifier;
@@ -640,6 +641,18 @@ public class ErrorVerifier extends RecursiveASTVisitor<Void> {
   }
 
   @Override
+  public Void visitFunctionExpressionInvocation(FunctionExpressionInvocation node) {
+    Expression functionExpression = node.getFunction();
+    Type expressionType = functionExpression.getStaticType();
+    if (!isFunctionType(expressionType)) {
+      errorReporter.reportError(
+          StaticTypeWarningCode.INVOCATION_OF_NON_FUNCTION_EXPRESSION,
+          functionExpression);
+    }
+    return super.visitFunctionExpressionInvocation(node);
+  }
+
+  @Override
   public Void visitFunctionTypeAlias(FunctionTypeAlias node) {
     checkForBuiltInIdentifierAsName(
         node.getName(),
@@ -4960,6 +4973,23 @@ public class ErrorVerifier extends RecursiveASTVisitor<Void> {
     }
   }
 
+  private boolean isFunctionType(Type type) {
+    if (type.isDynamic() || type == BottomTypeImpl.getInstance()) {
+      return true;
+    } else if (type instanceof InterfaceType) {
+      if (type == typeProvider.getFunctionType()) {
+        return true;
+      }
+      MethodElement callMethod = ((InterfaceType) type).lookUpMethod(
+          ElementResolver.CALL_METHOD_NAME,
+          currentLibrary);
+      return callMethod != null;
+    } else if (type instanceof FunctionType || type.isDartCoreFunction()) {
+      return true;
+    }
+    return false;
+  }
+
   /**
    * @return {@code true} if the given {@link ASTNode} is the part of constant constructor
    *         invocation.