Fix issue with ambient property declaration following property assignment in JS

src/compiler/utilities.ts

@@ -3524,8 +3524,8 @@ export function isSpecialPropertyDeclaration(expr: PropertyAccessExpression | El
 export function setValueDeclaration(symbol: Symbol, node: Declaration): void {
     const { valueDeclaration } = symbol;
     if (!valueDeclaration ||
-        !(node.flags & NodeFlags.Ambient && !(valueDeclaration.flags & NodeFlags.Ambient)) &&
-        (isAssignmentDeclaration(valueDeclaration) && !isAssignmentDeclaration(node)) ||
+        !(node.flags & NodeFlags.Ambient && !(valueDeclaration.flags & NodeFlags.Ambient)) && (isAssignmentDeclaration(valueDeclaration) && !isAssignmentDeclaration(node)) ||
+        node.kind === SyntaxKind.PropertyDeclaration && isAssignmentDeclaration(valueDeclaration) ||
         (valueDeclaration.kind !== node.kind && isEffectiveModuleDeclaration(valueDeclaration))) {
         // other kinds of value declarations take precedence over modules and assignment declarations
         symbol.valueDeclaration = node;

tests/baselines/reference/quickInfoAndSemanticsOnJsPropertyWithAmbientDeclaration.baseline

@@ -0,0 +1,35 @@
+Syntactic Diagnostics for file '/tests/cases/fourslash/quickInfoAndSemanticsOnJsPropertyWithAmbientDeclaration.ts':
+/test.js(6,5): error TS8009: The 'declare' modifier can only be used in TypeScript files.
+/test.js(6,19): error TS8010: Type annotations can only be used in TypeScript files.
+
+
+==== /test.js (2 errors) ====
+    class Foo {
+        constructor() {
+            this.prop = { };
+        }
+
+        declare prop: string;
+        ~~~~~~~
+!!! error TS8009: The 'declare' modifier can only be used in TypeScript files.
+                      ~~~~~~
+!!! error TS8010: Type annotations can only be used in TypeScript files.
+        method() {
+            this.prop.foo
+        }
+    }
+
+Semantic Diagnostics for file '/tests/cases/fourslash/quickInfoAndSemanticsOnJsPropertyWithAmbientDeclaration.ts':
+
+
+==== /test.js (0 errors) ====
+    class Foo {
+        constructor() {
+            this.prop = { };
+        }
+
+        declare prop: string;
+        method() {
+            this.prop.foo
+        }
+    }

tests/cases/fourslash/quickInfoAndSemanticsOnJsPropertyWithAmbientDeclaration.ts

@@ -0,0 +1,18 @@
+/// <reference path="fourslash.ts" />
+
+// @noLib: true
+// @allowJs: true
+// @filename: /test.js
+////class Foo {
+////    constructor() {
+////        this.prop = { };
+////    }
+////
+////    declare prop: string;
+////    method() {
+////        this.prop.foo/**/
+////    }
+////}
+
+verify.baselineQuickInfo();
+verify.baselineSyntacticAndSemanticDiagnostics();