Add tests

Author: ahejlsberg

tests/cases/conformance/types/mapped/isomorphicMappedTypeInference.ts

@@ -145,4 +145,11 @@ var g1 = applySpec({
 });
 
 // Infers g2: (...args: any[]) => { foo: { bar: { baz: boolean } } }
-var g2 = applySpec({ foo: { bar: { baz: (x: any) => true } } });
+var g2 = applySpec({ foo: { bar: { baz: (x: any) => true } } });
+
+// Repro from #12633
+
+const foo = <T>(object: T, partial: Partial<T>) => object;
+let o = {a: 5, b: 7};
+foo(o, {b: 9});
+o = foo(o, {b: 9});

tests/cases/conformance/types/mapped/mappedTypeErrors.ts

@@ -67,4 +67,21 @@ function f11<T>() {
 function f12<T>() {
     var x: { [P in keyof T]: T[P] };
     var x: { [P in keyof T]: T[P][] };  // Error
+}
+
+// Check that inferences to mapped types are secondary
+
+declare function objAndReadonly<T>(primary: T, secondary: Readonly<T>): T;
+declare function objAndPartial<T>(primary: T, secondary: Partial<T>): T;
+
+function f20() {
+    let x1 = objAndReadonly({ x: 0, y: 0 }, { x: 1 });  // Error
+    let x2 = objAndReadonly({ x: 0, y: 0 }, { x: 1, y: 1 });
+    let x3 = objAndReadonly({ x: 0, y: 0 }, { x: 1, y: 1, z: 1 });  // Error
+}
+
+function f21() {
+    let x1 = objAndPartial({ x: 0, y: 0 }, { x: 1 });
+    let x2 = objAndPartial({ x: 0, y: 0 }, { x: 1, y: 1 });
+    let x3 = objAndPartial({ x: 0, y: 0 }, { x: 1, y: 1, z: 1 });  // Error
 }