From 01a9e4f9be4eeebb1eb45350f6e55557035d7e38 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Thu, 26 Jan 2017 12:01:27 -0800
Subject: [PATCH] isOptionalParameter says unused IIFE arguments are optional

Related to adding undefined, though not strictly the same, this change
adds '?' to unused IIFE parameters in quick info.
---
 src/compiler/checker.ts                               | 8 +++++++-
 tests/baselines/reference/contextuallyTypedIife.types | 8 ++++----
 tests/cases/fourslash/quickInfoDisplayPartsIife.ts    | 5 +++++
 3 files changed, 16 insertions(+), 5 deletions(-)
 create mode 100644 tests/cases/fourslash/quickInfoDisplayPartsIife.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 22db0d32767..34d71a0ab6e 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -5145,6 +5145,12 @@ namespace ts {
                 Debug.assert(parameterIndex >= 0);
                 return parameterIndex >= signature.minArgumentCount;
             }
+            const iife = getImmediatelyInvokedFunctionExpression(node.parent);
+            if (iife) {
+                return !node.type &&
+                    !node.dotDotDotToken &&
+                    indexOf((node.parent as SignatureDeclaration).parameters, node) >= iife.arguments.length;
+            }
 
             return false;
         }
@@ -14026,7 +14032,7 @@ namespace ts {
                 return getTypeOfSymbol(symbol);
             }
         }
-
+
         function getTypeAtPosition(signature: Signature, pos: number): Type {
             return signature.hasRestParameter ?
                 pos < signature.parameters.length - 1 ? getTypeOfSymbol(signature.parameters[pos]) : getRestTypeOfSignature(signature) :
diff --git a/tests/baselines/reference/contextuallyTypedIife.types b/tests/baselines/reference/contextuallyTypedIife.types
index 15038e7dd26..676755fb341 100644
--- a/tests/baselines/reference/contextuallyTypedIife.types
+++ b/tests/baselines/reference/contextuallyTypedIife.types
@@ -253,8 +253,8 @@ let eleven = (o => o.a(11))({ a: function(n) { return n; } });
 // missing arguments
 (function(x, undefined) { return x; })(42);
 >(function(x, undefined) { return x; })(42) : number
->(function(x, undefined) { return x; }) : (x: number, undefined: any) => number
->function(x, undefined) { return x; } : (x: number, undefined: any) => number
+>(function(x, undefined) { return x; }) : (x: number, undefined?: any) => number
+>function(x, undefined) { return x; } : (x: number, undefined?: any) => number
 >x : number
 >undefined : any
 >x : number
@@ -262,8 +262,8 @@ let eleven = (o => o.a(11))({ a: function(n) { return n; } });
 
 ((x, y, z) => 42)();
 >((x, y, z) => 42)() : number
->((x, y, z) => 42) : (x: any, y: any, z: any) => number
->(x, y, z) => 42 : (x: any, y: any, z: any) => number
+>((x, y, z) => 42) : (x?: any, y?: any, z?: any) => number
+>(x, y, z) => 42 : (x?: any, y?: any, z?: any) => number
 >x : any
 >y : any
 >z : any
diff --git a/tests/cases/fourslash/quickInfoDisplayPartsIife.ts b/tests/cases/fourslash/quickInfoDisplayPartsIife.ts
new file mode 100644
index 00000000000..e4ce2bf96e3
--- /dev/null
+++ b/tests/cases/fourslash/quickInfoDisplayPartsIife.ts
@@ -0,0 +1,5 @@
+/// <reference path='fourslash.ts'/>
+// @strictNullChecks: true
+////var iife = (function foo/*1*/(x, y) { return x })(12);
+
+verify.quickInfoAt('1', '(local function) foo(x: number, y?: undefined): number');