Avoid circular reference in this-property assignments

src/compiler/checker.ts

@@ -7635,6 +7635,9 @@ namespace ts {
                 }
                 return anyType;
             }
+            if (containsSameNamedThisProperty(expression.left, expression.right)) {
+                return anyType;
+            }
             const type = resolvedSymbol ? getTypeOfSymbol(resolvedSymbol) : getWidenedLiteralType(checkExpressionCached(expression.right));
             if (type.flags & TypeFlags.Object &&
                 kind === AssignmentDeclarationKind.ModuleExports &&
@@ -7673,6 +7676,12 @@ namespace ts {
             return type;
         }
 
+        function containsSameNamedThisProperty(thisProperty: Expression, expression: Expression) {
+            return isPropertyAccessExpression(thisProperty)
+                && thisProperty.expression.kind === SyntaxKind.ThisKeyword
+                && forEachChildRecursively(expression, n => isMatchingReference(thisProperty, n));
+        }
+
         function isDeclarationInConstructor(expression: Expression) {
             const thisContainer = getThisContainer(expression, /*includeArrowFunctions*/ false);
             // Properties defined in a constructor (or base constructor, or javascript constructor function) don't get undefined added.

tests/baselines/reference/thisPropertyAssignmentCircular.js

@@ -0,0 +1,28 @@
+//// [thisPropertyAssignmentCircular.js]
+export class Foo {
+    constructor() {
+        this.foo = "Hello";
+    }
+    slicey() {
+        this.foo = this.foo.slice();
+    }
+    m() {
+        this.foo
+    }
+}
+
+/** @class */
+function C() {
+    this.x = 0;
+    this.x = function() { this.x.toString(); }
+}
+
+
+
+
+//// [thisPropertyAssignmentCircular.d.ts]
+export class Foo {
+    foo: string;
+    slicey(): void;
+    m(): void;
+}

tests/baselines/reference/thisPropertyAssignmentCircular.symbols

@@ -0,0 +1,51 @@
+=== tests/cases/conformance/salsa/thisPropertyAssignmentCircular.js ===
+export class Foo {
+>Foo : Symbol(Foo, Decl(thisPropertyAssignmentCircular.js, 0, 0))
+
+    constructor() {
+        this.foo = "Hello";
+>this.foo : Symbol(Foo.foo, Decl(thisPropertyAssignmentCircular.js, 1, 19), Decl(thisPropertyAssignmentCircular.js, 4, 14))
+>this : Symbol(Foo, Decl(thisPropertyAssignmentCircular.js, 0, 0))
+>foo : Symbol(Foo.foo, Decl(thisPropertyAssignmentCircular.js, 1, 19), Decl(thisPropertyAssignmentCircular.js, 4, 14))
+    }
+    slicey() {
+>slicey : Symbol(Foo.slicey, Decl(thisPropertyAssignmentCircular.js, 3, 5))
+
+        this.foo = this.foo.slice();
+>this.foo : Symbol(Foo.foo, Decl(thisPropertyAssignmentCircular.js, 1, 19), Decl(thisPropertyAssignmentCircular.js, 4, 14))
+>this : Symbol(Foo, Decl(thisPropertyAssignmentCircular.js, 0, 0))
+>foo : Symbol(Foo.foo, Decl(thisPropertyAssignmentCircular.js, 1, 19), Decl(thisPropertyAssignmentCircular.js, 4, 14))
+>this.foo.slice : Symbol(String.slice, Decl(lib.es5.d.ts, --, --))
+>this.foo : Symbol(Foo.foo, Decl(thisPropertyAssignmentCircular.js, 1, 19), Decl(thisPropertyAssignmentCircular.js, 4, 14))
+>this : Symbol(Foo, Decl(thisPropertyAssignmentCircular.js, 0, 0))
+>foo : Symbol(Foo.foo, Decl(thisPropertyAssignmentCircular.js, 1, 19), Decl(thisPropertyAssignmentCircular.js, 4, 14))
+>slice : Symbol(String.slice, Decl(lib.es5.d.ts, --, --))
+    }
+    m() {
+>m : Symbol(Foo.m, Decl(thisPropertyAssignmentCircular.js, 6, 5))
+
+        this.foo
+>this.foo : Symbol(Foo.foo, Decl(thisPropertyAssignmentCircular.js, 1, 19), Decl(thisPropertyAssignmentCircular.js, 4, 14))
+>this : Symbol(Foo, Decl(thisPropertyAssignmentCircular.js, 0, 0))
+>foo : Symbol(Foo.foo, Decl(thisPropertyAssignmentCircular.js, 1, 19), Decl(thisPropertyAssignmentCircular.js, 4, 14))
+    }
+}
+
+/** @class */
+function C() {
+>C : Symbol(C, Decl(thisPropertyAssignmentCircular.js, 10, 1))
+
+    this.x = 0;
+>this.x : Symbol(C.x, Decl(thisPropertyAssignmentCircular.js, 13, 14), Decl(thisPropertyAssignmentCircular.js, 14, 15))
+>this : Symbol(C, Decl(thisPropertyAssignmentCircular.js, 10, 1))
+>x : Symbol(C.x, Decl(thisPropertyAssignmentCircular.js, 13, 14), Decl(thisPropertyAssignmentCircular.js, 14, 15))
+
+    this.x = function() { this.x.toString(); }
+>this.x : Symbol(C.x, Decl(thisPropertyAssignmentCircular.js, 13, 14), Decl(thisPropertyAssignmentCircular.js, 14, 15))
+>this : Symbol(C, Decl(thisPropertyAssignmentCircular.js, 10, 1))
+>x : Symbol(C.x, Decl(thisPropertyAssignmentCircular.js, 13, 14), Decl(thisPropertyAssignmentCircular.js, 14, 15))
+>this.x : Symbol(C.x, Decl(thisPropertyAssignmentCircular.js, 13, 14), Decl(thisPropertyAssignmentCircular.js, 14, 15))
+>this : Symbol(C, Decl(thisPropertyAssignmentCircular.js, 10, 1))
+>x : Symbol(C.x, Decl(thisPropertyAssignmentCircular.js, 13, 14), Decl(thisPropertyAssignmentCircular.js, 14, 15))
+}
+

tests/baselines/reference/thisPropertyAssignmentCircular.types

@@ -0,0 +1,62 @@
+=== tests/cases/conformance/salsa/thisPropertyAssignmentCircular.js ===
+export class Foo {
+>Foo : Foo
+
+    constructor() {
+        this.foo = "Hello";
+>this.foo = "Hello" : "Hello"
+>this.foo : string
+>this : this
+>foo : string
+>"Hello" : "Hello"
+    }
+    slicey() {
+>slicey : () => void
+
+        this.foo = this.foo.slice();
+>this.foo = this.foo.slice() : string
+>this.foo : string
+>this : this
+>foo : string
+>this.foo.slice() : string
+>this.foo.slice : (start?: number, end?: number) => string
+>this.foo : string
+>this : this
+>foo : string
+>slice : (start?: number, end?: number) => string
+    }
+    m() {
+>m : () => void
+
+        this.foo
+>this.foo : string
+>this : this
+>foo : string
+    }
+}
+
+/** @class */
+function C() {
+>C : typeof C
+
+    this.x = 0;
+>this.x = 0 : 0
+>this.x : any
+>this : this
+>x : any
+>0 : 0
+
+    this.x = function() { this.x.toString(); }
+>this.x = function() { this.x.toString(); } : () => void
+>this.x : any
+>this : this
+>x : any
+>function() { this.x.toString(); } : () => void
+>this.x.toString() : any
+>this.x.toString : any
+>this.x : any
+>this : this
+>x : any
+>toString : any
+}
+

tests/cases/conformance/salsa/thisPropertyAssignmentCircular.ts

@@ -0,0 +1,22 @@
+// @allowJs: true
+// @checkJs: true
+// @declaration: true
+// @emitDeclarationOnly: true
+// @filename: thisPropertyAssignmentCircular.js
+export class Foo {
+    constructor() {
+        this.foo = "Hello";
+    }
+    slicey() {
+        this.foo = this.foo.slice();
+    }
+    m() {
+        this.foo
+    }
+}
+
+/** @class */
+function C() {
+    this.x = 0;
+    this.x = function() { this.x.toString(); }
+}