From 86315ed4119db22cc900b58d053f471d4d354119 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <Daniel.Rosenwasser@microsoft.com>
Date: Fri, 29 Sep 2017 22:01:00 -0700
Subject: [PATCH] Added test and adjusted reporting logic.

---
 src/compiler/checker.ts                       |  3 +-
 src/compiler/diagnosticMessages.json          |  2 +-
 src/compiler/emitter.ts                       |  0
 .../compiler/potentiallyUncalledDecorators.ts | 74 +++++++++++++++++++
 4 files changed, 77 insertions(+), 2 deletions(-)
 mode change 100755 => 100644 src/compiler/emitter.ts
 create mode 100644 tests/cases/compiler/potentiallyUncalledDecorators.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a272ac15e72..23da94437ae 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -16382,7 +16382,7 @@ namespace ts {
             }
 
             if (isPotentiallyUncalledDecorator(node, callSignatures)) {
-                error(node, Diagnostics.This_function_cannot_be_used_as_a_decorator_Did_you_mean_to_call_it_first);
+                error(node, Diagnostics.This_value_has_type_0_which_accepts_too_few_arguments_to_be_used_as_a_decorator_here_Did_you_mean_to_call_it_first, typeToString(funcType));
                 return resolveErrorCall(node);
             }
 
@@ -16406,6 +16406,7 @@ namespace ts {
         function isPotentiallyUncalledDecorator(decorator: Decorator, signatures: Signature[]) {
             return signatures.length && every(signatures, signature =>
                 signature.minArgumentCount === 0 &&
+                !signature.hasRestParameter &&
                 signature.parameters.length < getEffectiveArgumentCount(decorator, /*args*/ undefined, signature));
         }
 
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 722985aac78..57dc9f28834 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -907,7 +907,7 @@
         "category": "Error",
         "code": 1328
     },
-    "This function cannot be used as a decorator. Did you mean to call it first?": {
+    "This value has type '{0}' which accepts too few arguments to be used as a decorator here. Did you mean to call it first?": {
         "category": "Error",
         "code": 1329
     },
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
old mode 100755
new mode 100644
diff --git a/tests/cases/compiler/potentiallyUncalledDecorators.ts b/tests/cases/compiler/potentiallyUncalledDecorators.ts
new file mode 100644
index 00000000000..3c92a21eff0
--- /dev/null
+++ b/tests/cases/compiler/potentiallyUncalledDecorators.ts
@@ -0,0 +1,74 @@
+// @target: esnext
+// @module: esnext
+// @experimentalDecorators: true
+
+// Angular-style Input/Output API:
+declare function Input(bindingPropertyName?: string): any;
+class FooComponent {
+    @Input foo: string;
+}
+
+// Glimmer-style tracked API:
+declare const tracked: PropertyDecorator & { (...watchedProperties: string[]): any; }
+
+class Person {
+    @tracked person; any;
+}
+
+class MultiplyByTwo {
+    args: any;
+    @tracked('args')
+    get multiplied() {
+        return this.args.number * 2;
+    }
+}
+
+// Other fun stuff.
+
+interface OmniDecorator extends MethodDecorator, ClassDecorator, PropertyDecorator {
+}
+
+declare function noArgs(): OmniDecorator;
+declare function allRest(...args: any[]): OmniDecorator;
+declare function oneOptional(x?: any): OmniDecorator;
+declare function twoOptional(x?: any, y?: any): OmniDecorator;
+declare function threeOptional(x?: any, y?: any, z?: any): OmniDecorator;
+declare function oneOptionalWithRest(x?: any, ...args: any[]): OmniDecorator;
+
+@noArgs
+class A {
+    @noArgs foo: any;
+    @noArgs bar() { }
+}
+
+@allRest
+class B {
+    @allRest foo: any;
+    @allRest bar() { }
+}
+
+@oneOptional
+class C {
+    @oneOptional foo: any;
+    @oneOptional bar() { }
+}
+
+@twoOptional
+class D {
+    @twoOptional foo: any;
+    @twoOptional bar() { }
+}
+
+@threeOptional
+class E {
+    @threeOptional foo: any;
+    @threeOptional bar() { }
+}
+
+@oneOptionalWithRest
+class F {
+    @oneOptionalWithRest foo: any;
+    @oneOptionalWithRest bar() { }
+}
+
+export { };