Check this expressions in object literal methods

Add a test and baseline

src/compiler/checker.ts

@@ -7494,6 +7494,14 @@ namespace ts {
                 const symbol = getSymbolOfNode(container.parent);
                 return container.flags & NodeFlags.Static ? getTypeOfSymbol(symbol) : (<InterfaceType>getDeclaredTypeOfSymbol(symbol)).thisType;
             }
+            if (container.parent && container.parent.kind === SyntaxKind.ObjectLiteralExpression) {
+                // Note: this works because object literal methods are deferred,
+                // which means that the type of the containing object literal is already known.
+                const type = checkExpressionCached(<ObjectLiteralExpression>container.parent);
+                if (type) {
+                    return type;
+                }
+            }
 
             if (isInJavaScriptFile(node)) {
                 const type = getTypeForThisExpressionFromJSDoc(container);

tests/baselines/reference/thisTypeInObjectLiterals.js

@@ -0,0 +1,16 @@
+//// [thisTypeInObjectLiterals.ts]
+let o = {
+    d: "bar",
+    m() {
+        return this.d.length;
+    }
+}
+
+
+//// [thisTypeInObjectLiterals.js]
+var o = {
+    d: "bar",
+    m: function () {
+        return this.d.length;
+    }
+};

tests/baselines/reference/thisTypeInObjectLiterals.symbols

@@ -0,0 +1,19 @@
+=== tests/cases/conformance/types/thisType/thisTypeInObjectLiterals.ts ===
+let o = {
+>o : Symbol(o, Decl(thisTypeInObjectLiterals.ts, 0, 3))
+
+    d: "bar",
+>d : Symbol(d, Decl(thisTypeInObjectLiterals.ts, 0, 9))
+
+    m() {
+>m : Symbol(m, Decl(thisTypeInObjectLiterals.ts, 1, 13))
+
+        return this.d.length;
+>this.d.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>this.d : Symbol(d, Decl(thisTypeInObjectLiterals.ts, 0, 9))
+>this : Symbol(, Decl(thisTypeInObjectLiterals.ts, 0, 7))
+>d : Symbol(d, Decl(thisTypeInObjectLiterals.ts, 0, 9))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+    }
+}
+

tests/baselines/reference/thisTypeInObjectLiterals.types

@@ -0,0 +1,21 @@
+=== tests/cases/conformance/types/thisType/thisTypeInObjectLiterals.ts ===
+let o = {
+>o : { d: string; m(): number; }
+>{    d: "bar",    m() {        return this.d.length;    }} : { d: string; m(): number; }
+
+    d: "bar",
+>d : string
+>"bar" : string
+
+    m() {
+>m : () => number
+
+        return this.d.length;
+>this.d.length : number
+>this.d : string
+>this : { d: string; m(): number; }
+>d : string
+>length : number
+    }
+}
+

tests/cases/conformance/types/thisType/thisTypeInObjectLiterals.ts

@@ -0,0 +1,6 @@
+let o = {
+    d: "bar",
+    m() {
+        return this.d.length;
+    }
+}