Property assignment is not an assignment target

In a destructuring assignment, a property assignment is not an
assignment target. Its initialiser is. For example:

```ts
({ source: target} = o);
```

Here, `target` is the assignment target. `source` is not. Previously,
both were assignment targets.

Author: sandersn

src/compiler/utilities.ts

@@ -1662,11 +1662,15 @@ namespace ts {
                     node = parent;
                     break;
                 case SyntaxKind.ShorthandPropertyAssignment:
-                    if ((<ShorthandPropertyAssignment>parent).name !== node) {
+                    if ((parent as ShorthandPropertyAssignment).name !== node) {
                         return AssignmentKind.None;
                     }
-                // Fall through
+                    node = parent.parent;
+                    break;
                 case SyntaxKind.PropertyAssignment:
+                    if ((parent as ShorthandPropertyAssignment).name === node) {
+                        return AssignmentKind.None;
+                    }
                     node = parent.parent;
                     break;
                 default:
@@ -1678,7 +1682,8 @@ namespace ts {
 
     // A node is an assignment target if it is on the left hand side of an '=' token, if it is parented by a property
     // assignment in an object literal that is an assignment target, or if it is parented by an array literal that is
-    // an assignment target. Examples include 'a = xxx', '{ p: a } = xxx', '[{ p: a}] = xxx'.
+    // an assignment target. Examples include 'a = xxx', '{ p: a } = xxx', '[{ a }] = xxx'.
+    // (Note that `p` is not a target in the above examples, only `a`.)
     export function isAssignmentTarget(node: Node): boolean {
         return getAssignmentTargetKind(node) !== AssignmentKind.None;
     }

tests/baselines/reference/destructuringPropertyAssignmentNameIsNotAssignmentTarget.js

@@ -0,0 +1,17 @@
+//// [destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts]
+// test for #10668
+function qux(bar: { value: number }) {
+    let foo: number;
+    ({ value: foo } = bar);
+    let x = () => bar;
+}
+
+
+
+//// [destructuringPropertyAssignmentNameIsNotAssignmentTarget.js]
+// test for #10668
+function qux(bar) {
+    var foo;
+    (foo = bar.value);
+    var x = function () { return bar; };
+}

tests/baselines/reference/destructuringPropertyAssignmentNameIsNotAssignmentTarget.symbols

@@ -0,0 +1,21 @@
+=== tests/cases/compiler/destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts ===
+// test for #10668
+function qux(bar: { value: number }) {
+>qux : Symbol(qux, Decl(destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts, 0, 0))
+>bar : Symbol(bar, Decl(destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts, 1, 13))
+>value : Symbol(value, Decl(destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts, 1, 19))
+
+    let foo: number;
+>foo : Symbol(foo, Decl(destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts, 2, 7))
+
+    ({ value: foo } = bar);
+>value : Symbol(value, Decl(destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts, 3, 6))
+>foo : Symbol(foo, Decl(destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts, 2, 7))
+>bar : Symbol(bar, Decl(destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts, 1, 13))
+
+    let x = () => bar;
+>x : Symbol(x, Decl(destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts, 4, 7))
+>bar : Symbol(bar, Decl(destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts, 1, 13))
+}
+
+

tests/baselines/reference/destructuringPropertyAssignmentNameIsNotAssignmentTarget.types

@@ -0,0 +1,25 @@
+=== tests/cases/compiler/destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts ===
+// test for #10668
+function qux(bar: { value: number }) {
+>qux : (bar: { value: number; }) => void
+>bar : { value: number; }
+>value : number
+
+    let foo: number;
+>foo : number
+
+    ({ value: foo } = bar);
+>({ value: foo } = bar) : { value: number; }
+>{ value: foo } = bar : { value: number; }
+>{ value: foo } : { value: number; }
+>value : number
+>foo : number
+>bar : { value: number; }
+
+    let x = () => bar;
+>x : () => { value: number; }
+>() => bar : () => { value: number; }
+>bar : { value: number; }
+}
+
+

tests/cases/compiler/destructuringPropertyAssignmentNameIsNotAssignmentTarget.ts

@@ -0,0 +1,7 @@
+// test for #10668
+function qux(bar: { value: number }) {
+    let foo: number;
+    ({ value: foo } = bar);
+    let x = () => bar;
+}
+