Fixes #17080

https://github.com/Microsoft/TypeScript/issues/17080
Added testcases from the Github bugreport (all working as intended now).
Signed CLA.

pull_request_template.md

@@ -6,7 +6,7 @@ Here's a checklist you might find useful.
   'Bug' or 'help wanted' or is in the Community milestone
 [X] Code is up-to-date with the `master` branch
 [X] You've successfully run `jake runtests` locally
-[ ] You've signed the CLA
+[X] You've signed the CLA
 [X] There are new or updated unit tests validating the change
 
 Refer to CONTRIBUTING.MD for more details.

tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt

@@ -6,9 +6,13 @@ tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(21,7): e
   Type 'undefined' is not assignable to type 'number'.
 tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(31,8): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
   Type 'undefined' is not assignable to type 'number'.
+tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(45,10): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+  Type 'undefined' is not assignable to type 'number'.
+tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(55,11): error TS2345: Argument of type 'number | null' is not assignable to parameter of type 'number | undefined'.
+  Type 'null' is not assignable to type 'number | undefined'.
 
 
-==== tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts (4 errors) ====
+==== tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts (6 errors) ====
     // https://github.com/Microsoft/TypeScript/issues/17080
     function f(a:number,b:number) {
     }
@@ -59,4 +63,36 @@ tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(31,8): e
       f(b, c)
       // no error
     }
+    
+    interface Foo {
+      readonly bar?: number;
+    }
+    
+    function performFoo({ bar }: Foo = {}) {
+      useBar(bar);
+             ~~~
+!!! error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+!!! error TS2345:   Type 'undefined' is not assignable to type 'number'.
+    }
+    
+    function useBar(bar: number) {
+      f(bar, 1)
+    }
+    
+    performFoo();
+    
+    function performFoo2({ bar = null }: Foo = {}) {
+      useBar2(bar);
+              ~~~
+!!! error TS2345: Argument of type 'number | null' is not assignable to parameter of type 'number | undefined'.
+!!! error TS2345:   Type 'null' is not assignable to type 'number | undefined'.
+    }
+    
+    function useBar2(bar: number | undefined) {
+      if (bar) {
+        f(bar, 1)
+      }
+    }
+    
+    performFoo2();
     

tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js

@@ -37,6 +37,32 @@ function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number},
   f(b, c)
   // no error
 }
+
+interface Foo {
+  readonly bar?: number;
+}
+
+function performFoo({ bar }: Foo = {}) {
+  useBar(bar);
+}
+
+function useBar(bar: number) {
+  f(bar, 1)
+}
+
+performFoo();
+
+function performFoo2({ bar = null }: Foo = {}) {
+  useBar2(bar);
+}
+
+function useBar2(bar: number | undefined) {
+  if (bar) {
+    f(bar, 1)
+  }
+}
+
+performFoo2();
 
 
 //// [optionalParameterInDestructuringWithInitializer.js]
@@ -78,3 +104,21 @@ function func7(_a) {
     f(b, c);
     // no error
 }
+function performFoo(_a) {
+    var bar = (_a === void 0 ? {} : _a).bar;
+    useBar(bar);
+}
+function useBar(bar) {
+    f(bar, 1);
+}
+performFoo();
+function performFoo2(_a) {
+    var _b = (_a === void 0 ? {} : _a).bar, bar = _b === void 0 ? null : _b;
+    useBar2(bar);
+}
+function useBar2(bar) {
+    if (bar) {
+        f(bar, 1);
+    }
+}
+performFoo2();

tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols

@@ -152,3 +152,58 @@ function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number},
   // no error
 }
 
+interface Foo {
+>Foo : Symbol(Foo, Decl(optionalParameterInDestructuringWithInitializer.ts, 37, 1))
+
+  readonly bar?: number;
+>bar : Symbol(Foo.bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 39, 15))
+}
+
+function performFoo({ bar }: Foo = {}) {
+>performFoo : Symbol(performFoo, Decl(optionalParameterInDestructuringWithInitializer.ts, 41, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 43, 21))
+>Foo : Symbol(Foo, Decl(optionalParameterInDestructuringWithInitializer.ts, 37, 1))
+
+  useBar(bar);
+>useBar : Symbol(useBar, Decl(optionalParameterInDestructuringWithInitializer.ts, 45, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 43, 21))
+}
+
+function useBar(bar: number) {
+>useBar : Symbol(useBar, Decl(optionalParameterInDestructuringWithInitializer.ts, 45, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 47, 16))
+
+  f(bar, 1)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 47, 16))
+}
+
+performFoo();
+>performFoo : Symbol(performFoo, Decl(optionalParameterInDestructuringWithInitializer.ts, 41, 1))
+
+function performFoo2({ bar = null }: Foo = {}) {
+>performFoo2 : Symbol(performFoo2, Decl(optionalParameterInDestructuringWithInitializer.ts, 51, 13))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 53, 22))
+>Foo : Symbol(Foo, Decl(optionalParameterInDestructuringWithInitializer.ts, 37, 1))
+
+  useBar2(bar);
+>useBar2 : Symbol(useBar2, Decl(optionalParameterInDestructuringWithInitializer.ts, 55, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 53, 22))
+}
+
+function useBar2(bar: number | undefined) {
+>useBar2 : Symbol(useBar2, Decl(optionalParameterInDestructuringWithInitializer.ts, 55, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 57, 17))
+
+  if (bar) {
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 57, 17))
+
+    f(bar, 1)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 57, 17))
+  }
+}
+
+performFoo2();
+>performFoo2 : Symbol(performFoo2, Decl(optionalParameterInDestructuringWithInitializer.ts, 51, 13))
+

tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types

@@ -196,3 +196,69 @@ function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number},
   // no error
 }
 
+interface Foo {
+>Foo : Foo
+
+  readonly bar?: number;
+>bar : number | undefined
+}
+
+function performFoo({ bar }: Foo = {}) {
+>performFoo : ({ bar }?: Foo) => void
+>bar : number | undefined
+>Foo : Foo
+>{} : {}
+
+  useBar(bar);
+>useBar(bar) : void
+>useBar : (bar: number) => void
+>bar : number | undefined
+}
+
+function useBar(bar: number) {
+>useBar : (bar: number) => void
+>bar : number
+
+  f(bar, 1)
+>f(bar, 1) : void
+>f : (a: number, b: number) => void
+>bar : number
+>1 : 1
+}
+
+performFoo();
+>performFoo() : void
+>performFoo : ({ bar }?: Foo) => void
+
+function performFoo2({ bar = null }: Foo = {}) {
+>performFoo2 : ({ bar }?: Foo) => void
+>bar : number | null
+>null : null
+>Foo : Foo
+>{} : {}
+
+  useBar2(bar);
+>useBar2(bar) : void
+>useBar2 : (bar: number | undefined) => void
+>bar : number | null
+}
+
+function useBar2(bar: number | undefined) {
+>useBar2 : (bar: number | undefined) => void
+>bar : number | undefined
+
+  if (bar) {
+>bar : number | undefined
+
+    f(bar, 1)
+>f(bar, 1) : void
+>f : (a: number, b: number) => void
+>bar : number
+>1 : 1
+  }
+}
+
+performFoo2();
+>performFoo2() : void
+>performFoo2 : ({ bar }?: Foo) => void
+

tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts

@@ -37,3 +37,29 @@ function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number},
   f(b, c)
   // no error
 }
+
+interface Foo {
+  readonly bar?: number;
+}
+
+function performFoo({ bar }: Foo = {}) {
+  useBar(bar);
+}
+
+function useBar(bar: number) {
+  f(bar, 1)
+}
+
+performFoo();
+
+function performFoo2({ bar = null }: Foo = {}) {
+  useBar2(bar);
+}
+
+function useBar2(bar: number | undefined) {
+  if (bar) {
+    f(bar, 1)
+  }
+}
+
+performFoo2();