No this-property assignments in TS

Even when `this` is aliased, which I mistakenly allowed in #39908.

Author: sandersn

src/compiler/binder.ts

@@ -2487,7 +2487,7 @@ namespace ts {
                             break;
                         case AssignmentDeclarationKind.Property:
                             const expression = ((node as BinaryExpression).left as AccessExpression).expression;
-                            if (isIdentifier(expression)) {
+                            if (isInJSFile(node) && isIdentifier(expression)) {
                                 const symbol = lookupSymbolForName(blockScopeContainer, expression.escapedText);
                                 if (isThisInitializedDeclaration(symbol?.valueDeclaration)) {
                                     bindThisPropertyAssignment(node as BindablePropertyAssignmentExpression);

tests/baselines/reference/inferringClassMembersFromAssignments8.js

@@ -0,0 +1,19 @@
+//// [inferringClassMembersFromAssignments8.ts]
+// no inference in TS files, even for `this` aliases:
+
+var app = function() {
+    var _this = this;
+    _this.swap = function() { }
+}
+var a = new app()
+a
+
+
+//// [inferringClassMembersFromAssignments8.js]
+// no inference in TS files, even for `this` aliases:
+var app = function () {
+    var _this = this;
+    _this.swap = function () { };
+};
+var a = new app();
+a;

tests/baselines/reference/inferringClassMembersFromAssignments8.symbols

@@ -0,0 +1,19 @@
+=== tests/cases/conformance/salsa/inferringClassMembersFromAssignments8.ts ===
+// no inference in TS files, even for `this` aliases:
+
+var app = function() {
+>app : Symbol(app, Decl(inferringClassMembersFromAssignments8.ts, 2, 3))
+
+    var _this = this;
+>_this : Symbol(_this, Decl(inferringClassMembersFromAssignments8.ts, 3, 7))
+
+    _this.swap = function() { }
+>_this : Symbol(_this, Decl(inferringClassMembersFromAssignments8.ts, 3, 7))
+}
+var a = new app()
+>a : Symbol(a, Decl(inferringClassMembersFromAssignments8.ts, 6, 3))
+>app : Symbol(app, Decl(inferringClassMembersFromAssignments8.ts, 2, 3))
+
+a
+>a : Symbol(a, Decl(inferringClassMembersFromAssignments8.ts, 6, 3))
+

tests/baselines/reference/inferringClassMembersFromAssignments8.types

@@ -0,0 +1,26 @@
+=== tests/cases/conformance/salsa/inferringClassMembersFromAssignments8.ts ===
+// no inference in TS files, even for `this` aliases:
+
+var app = function() {
+>app : () => void
+>function() {    var _this = this;    _this.swap = function() { }} : () => void
+
+    var _this = this;
+>_this : any
+>this : any
+
+    _this.swap = function() { }
+>_this.swap = function() { } : () => void
+>_this.swap : any
+>_this : any
+>swap : any
+>function() { } : () => void
+}
+var a = new app()
+>a : any
+>new app() : any
+>app : () => void
+
+a
+>a : any
+

tests/cases/conformance/salsa/inferringClassMembersFromAssignments8.ts

@@ -0,0 +1,8 @@
+// no inference in TS files, even for `this` aliases:
+
+var app = function() {
+    var _this = this;
+    _this.swap = function() { }
+}
+var a = new app()
+a

tests/cases/conformance/salsa/veryBerry.ts

@@ -0,0 +1,33 @@
+// @noEmit: true
+// @allowJs: true
+// @checkJs: true
+// @filename: mod1.js
+// @esModuleInterop: true
+
+const x = function() { }
+module.exports.x = x
+// @filename: use1.js
+const { x } = require('./mod1')
+x
+
+// @filename: mod2.js
+const x = function() { }
+module.exports = x
+// @filename: use2.js
+const x = require('./mod2')
+x
+
+// @filename: mod3.js
+const x = function() { }
+export { x }
+// @filename: use3.js
+import { x } from './mod3'
+x
+
+// @filename: mod4.js
+const x = function() { }
+export default x
+// @filename: use4.js
+import x from './mod4'
+x
+