In JS, assignment to void 0 isn't a declaration

src/compiler/utilities.ts

@@ -2220,7 +2220,7 @@ namespace ts {
             }
             return AssignmentDeclarationKind.ObjectDefinePropertyValue;
         }
-        if (expr.operatorToken.kind !== SyntaxKind.EqualsToken || !isAccessExpression(expr.left)) {
+        if (expr.operatorToken.kind !== SyntaxKind.EqualsToken || !isAccessExpression(expr.left) || isVoidZero(getRightMostAssignedExpression(expr))) {
             return AssignmentDeclarationKind.None;
         }
         if (isBindableStaticNameExpression(expr.left.expression, /*excludeThisKeyword*/ true) && getElementOrPropertyAccessName(expr.left) === "prototype" && isObjectLiteralExpression(getInitializerOfBinaryExpression(expr))) {
@@ -2230,6 +2230,10 @@ namespace ts {
         return getAssignmentDeclarationPropertyAccessKind(expr.left);
     }
 
+    function isVoidZero(node: Node) {
+        return isVoidExpression(node) && isNumericLiteral(node.expression) && node.expression.text === "0";
+    }
+
     /**
      * Does not handle signed numeric names like `a[+0]` - handling those would require handling prefix unary expressions
      * throughout late binding handling as well, which is awkward (but ultimately probably doable if there is demand)

tests/baselines/reference/assignmentToVoidZero1.js

@@ -0,0 +1,17 @@
+//// [assignmentToVoidZero1.js]
+// #38552
+exports.y = exports.x = void 0;
+exports.x = 1;
+exports.y = 2;
+
+
+//// [assignmentToVoidZero1.js]
+// #38552
+exports.y = exports.x = void 0;
+exports.x = 1;
+exports.y = 2;
+
+
+//// [assignmentToVoidZero1.d.ts]
+export var x: number;
+export var y: number;

tests/baselines/reference/assignmentToVoidZero1.symbols

@@ -0,0 +1,20 @@
+=== tests/cases/conformance/salsa/assignmentToVoidZero1.js ===
+// #38552
+exports.y = exports.x = void 0;
+>exports.y : Symbol(y, Decl(assignmentToVoidZero1.js, 2, 14))
+>exports : Symbol("tests/cases/conformance/salsa/assignmentToVoidZero1", Decl(assignmentToVoidZero1.js, 0, 0))
+>y : Symbol(y, Decl(assignmentToVoidZero1.js, 2, 14))
+>exports.x : Symbol(x, Decl(assignmentToVoidZero1.js, 1, 31))
+>exports : Symbol("tests/cases/conformance/salsa/assignmentToVoidZero1", Decl(assignmentToVoidZero1.js, 0, 0))
+>x : Symbol(x, Decl(assignmentToVoidZero1.js, 1, 31))
+
+exports.x = 1;
+>exports.x : Symbol(x, Decl(assignmentToVoidZero1.js, 1, 31))
+>exports : Symbol(x, Decl(assignmentToVoidZero1.js, 1, 31))
+>x : Symbol(x, Decl(assignmentToVoidZero1.js, 1, 31))
+
+exports.y = 2;
+>exports.y : Symbol(y, Decl(assignmentToVoidZero1.js, 2, 14))
+>exports : Symbol(y, Decl(assignmentToVoidZero1.js, 2, 14))
+>y : Symbol(y, Decl(assignmentToVoidZero1.js, 2, 14))
+

tests/baselines/reference/assignmentToVoidZero1.types

@@ -0,0 +1,28 @@
+=== tests/cases/conformance/salsa/assignmentToVoidZero1.js ===
+// #38552
+exports.y = exports.x = void 0;
+>exports.y = exports.x = void 0 : undefined
+>exports.y : number
+>exports : typeof import("tests/cases/conformance/salsa/assignmentToVoidZero1")
+>y : number
+>exports.x = void 0 : undefined
+>exports.x : number
+>exports : typeof import("tests/cases/conformance/salsa/assignmentToVoidZero1")
+>x : number
+>void 0 : undefined
+>0 : 0
+
+exports.x = 1;
+>exports.x = 1 : 1
+>exports.x : number
+>exports : typeof import("tests/cases/conformance/salsa/assignmentToVoidZero1")
+>x : number
+>1 : 1
+
+exports.y = 2;
+>exports.y = 2 : 2
+>exports.y : number
+>exports : typeof import("tests/cases/conformance/salsa/assignmentToVoidZero1")
+>y : number
+>2 : 2
+

tests/baselines/reference/assignmentToVoidZero2.errors.txt

@@ -0,0 +1,36 @@
+tests/cases/conformance/salsa/assignmentToVoidZero2.js(2,9): error TS2339: Property 'k' does not exist on type 'typeof import("tests/cases/conformance/salsa/assignmentToVoidZero2")'.
+tests/cases/conformance/salsa/assignmentToVoidZero2.js(5,3): error TS2339: Property 'y' does not exist on type 'typeof o'.
+tests/cases/conformance/salsa/assignmentToVoidZero2.js(6,9): error TS2339: Property 'y' does not exist on type 'typeof o'.
+tests/cases/conformance/salsa/assignmentToVoidZero2.js(13,9): error TS2339: Property 'q' does not exist on type 'C'.
+tests/cases/conformance/salsa/importer.js(1,13): error TS2305: Module '"./assignmentToVoidZero2"' has no exported member 'k'.
+
+
+==== tests/cases/conformance/salsa/assignmentToVoidZero2.js (4 errors) ====
+    exports.j = 1;
+    exports.k = void 0;
+            ~
+!!! error TS2339: Property 'k' does not exist on type 'typeof import("tests/cases/conformance/salsa/assignmentToVoidZero2")'.
+    var o = {}
+    o.x = 1
+    o.y = void 0
+      ~
+!!! error TS2339: Property 'y' does not exist on type 'typeof o'.
+    o.x + o.y
+            ~
+!!! error TS2339: Property 'y' does not exist on type 'typeof o'.
+
+    function C() {
+        this.p = 1
+        this.q = void 0
+    }
+    var c = new C()
+    c.p + c.q
+            ~
+!!! error TS2339: Property 'q' does not exist on type 'C'.
+
+==== tests/cases/conformance/salsa/importer.js (1 errors) ====
+    import { j, k } from './assignmentToVoidZero2'
+                ~
+!!! error TS2305: Module '"./assignmentToVoidZero2"' has no exported member 'k'.
+    j + k
+

tests/baselines/reference/assignmentToVoidZero2.js

@@ -0,0 +1,46 @@
+//// [tests/cases/conformance/salsa/assignmentToVoidZero2.ts] ////
+
+//// [assignmentToVoidZero2.js]
+exports.j = 1;
+exports.k = void 0;
+var o = {}
+o.x = 1
+o.y = void 0
+o.x + o.y
+
+function C() {
+    this.p = 1
+    this.q = void 0
+}
+var c = new C()
+c.p + c.q
+
+//// [importer.js]
+import { j, k } from './assignmentToVoidZero2'
+j + k
+
+
+//// [assignmentToVoidZero2.js]
+exports.j = 1;
+exports.k = void 0;
+var o = {};
+o.x = 1;
+o.y = void 0;
+o.x + o.y;
+function C() {
+    this.p = 1;
+    this.q = void 0;
+}
+var c = new C();
+c.p + c.q;
+//// [importer.js]
+"use strict";
+exports.__esModule = true;
+var assignmentToVoidZero2_1 = require("./assignmentToVoidZero2");
+assignmentToVoidZero2_1.j + assignmentToVoidZero2_1.k;
+
+
+//// [assignmentToVoidZero2.d.ts]
+export var j: number;
+//// [importer.d.ts]
+export {};

tests/baselines/reference/assignmentToVoidZero2.symbols

@@ -0,0 +1,53 @@
+=== tests/cases/conformance/salsa/assignmentToVoidZero2.js ===
+exports.j = 1;
+>exports.j : Symbol(j, Decl(assignmentToVoidZero2.js, 0, 0))
+>exports : Symbol(j, Decl(assignmentToVoidZero2.js, 0, 0))
+>j : Symbol(j, Decl(assignmentToVoidZero2.js, 0, 0))
+
+exports.k = void 0;
+>exports : Symbol("tests/cases/conformance/salsa/assignmentToVoidZero2", Decl(assignmentToVoidZero2.js, 0, 0))
+
+var o = {}
+>o : Symbol(o, Decl(assignmentToVoidZero2.js, 2, 3), Decl(assignmentToVoidZero2.js, 2, 10))
+
+o.x = 1
+>o.x : Symbol(o.x, Decl(assignmentToVoidZero2.js, 2, 10))
+>o : Symbol(o, Decl(assignmentToVoidZero2.js, 2, 3), Decl(assignmentToVoidZero2.js, 2, 10))
+>x : Symbol(o.x, Decl(assignmentToVoidZero2.js, 2, 10))
+
+o.y = void 0
+>o : Symbol(o, Decl(assignmentToVoidZero2.js, 2, 3), Decl(assignmentToVoidZero2.js, 2, 10))
+
+o.x + o.y
+>o.x : Symbol(o.x, Decl(assignmentToVoidZero2.js, 2, 10))
+>o : Symbol(o, Decl(assignmentToVoidZero2.js, 2, 3), Decl(assignmentToVoidZero2.js, 2, 10))
+>x : Symbol(o.x, Decl(assignmentToVoidZero2.js, 2, 10))
+>o : Symbol(o, Decl(assignmentToVoidZero2.js, 2, 3), Decl(assignmentToVoidZero2.js, 2, 10))
+
+function C() {
+>C : Symbol(C, Decl(assignmentToVoidZero2.js, 5, 9))
+
+    this.p = 1
+>p : Symbol(C.p, Decl(assignmentToVoidZero2.js, 7, 14))
+
+    this.q = void 0
+}
+var c = new C()
+>c : Symbol(c, Decl(assignmentToVoidZero2.js, 11, 3))
+>C : Symbol(C, Decl(assignmentToVoidZero2.js, 5, 9))
+
+c.p + c.q
+>c.p : Symbol(C.p, Decl(assignmentToVoidZero2.js, 7, 14))
+>c : Symbol(c, Decl(assignmentToVoidZero2.js, 11, 3))
+>p : Symbol(C.p, Decl(assignmentToVoidZero2.js, 7, 14))
+>c : Symbol(c, Decl(assignmentToVoidZero2.js, 11, 3))
+
+=== tests/cases/conformance/salsa/importer.js ===
+import { j, k } from './assignmentToVoidZero2'
+>j : Symbol(j, Decl(importer.js, 0, 8))
+>k : Symbol(k, Decl(importer.js, 0, 11))
+
+j + k
+>j : Symbol(j, Decl(importer.js, 0, 8))
+>k : Symbol(k, Decl(importer.js, 0, 11))
+

tests/baselines/reference/assignmentToVoidZero2.types

@@ -0,0 +1,86 @@
+=== tests/cases/conformance/salsa/assignmentToVoidZero2.js ===
+exports.j = 1;
+>exports.j = 1 : 1
+>exports.j : number
+>exports : typeof import("tests/cases/conformance/salsa/assignmentToVoidZero2")
+>j : number
+>1 : 1
+
+exports.k = void 0;
+>exports.k = void 0 : undefined
+>exports.k : any
+>exports : typeof import("tests/cases/conformance/salsa/assignmentToVoidZero2")
+>k : any
+>void 0 : undefined
+>0 : 0
+
+var o = {}
+>o : typeof o
+>{} : {}
+
+o.x = 1
+>o.x = 1 : 1
+>o.x : number
+>o : typeof o
+>x : number
+>1 : 1
+
+o.y = void 0
+>o.y = void 0 : undefined
+>o.y : any
+>o : typeof o
+>y : any
+>void 0 : undefined
+>0 : 0
+
+o.x + o.y
+>o.x + o.y : any
+>o.x : number
+>o : typeof o
+>x : number
+>o.y : any
+>o : typeof o
+>y : any
+
+function C() {
+>C : typeof C
+
+    this.p = 1
+>this.p = 1 : 1
+>this.p : any
+>this : any
+>p : any
+>1 : 1
+
+    this.q = void 0
+>this.q = void 0 : undefined
+>this.q : any
+>this : any
+>q : any
+>void 0 : undefined
+>0 : 0
+}
+var c = new C()
+>c : C
+>new C() : C
+>C : typeof C
+
+c.p + c.q
+>c.p + c.q : any
+>c.p : number
+>c : C
+>p : number
+>c.q : any
+>c : C
+>q : any
+
+=== tests/cases/conformance/salsa/importer.js ===
+import { j, k } from './assignmentToVoidZero2'
+>j : number
+>k : any
+
+j + k
+>j + k : any
+>j : number
+>k : any
+

tests/cases/conformance/salsa/assignmentToVoidZero1.ts

@@ -0,0 +1,11 @@
+// @filename: assignmentToVoidZero1.js
+// @declaration: true
+// @module: commonjs
+// @outdir: auss
+// @checkJs: true
+// @allowJs: true
+
+// #38552
+exports.y = exports.x = void 0;
+exports.x = 1;
+exports.y = 2;

tests/cases/conformance/salsa/assignmentToVoidZero2.ts

@@ -0,0 +1,24 @@
+// @filename: assignmentToVoidZero2.js
+// @declaration: true
+// @module: commonjs
+// @outdir: auss
+// @checkJs: true
+// @allowJs: true
+// @noImplicitAny: true
+exports.j = 1;
+exports.k = void 0;
+var o = {}
+o.x = 1
+o.y = void 0
+o.x + o.y
+
+function C() {
+    this.p = 1
+    this.q = void 0
+}
+var c = new C()
+c.p + c.q
+
+// @filename: importer.js
+import { j, k } from './assignmentToVoidZero2'
+j + k