Added tests.

tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloadAssignability01.ts

@@ -0,0 +1,17 @@
+// @declaration: true
+
+function f(x: "foo"): number;
+function f(x: string): number {
+    return 0;
+}
+
+function g(x: "bar"): number;
+function g(x: string): number {
+    return 0;
+}
+
+let a = f;
+let b = g;
+
+a = b;
+b = a;

tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloadAssignability02.ts

@@ -0,0 +1,17 @@
+// @declaration: true
+
+function f(x: "foo"): number;
+function f(x: "foo"): number {
+    return 0;
+}
+
+function g(x: "bar"): number;
+function g(x: "bar"): number {
+    return 0;
+}
+
+let a = f;
+let b = g;
+
+a = b;
+b = a;

tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloadAssignability03.ts

@@ -0,0 +1,17 @@
+// @declaration: true
+
+function f(x: "foo"): number;
+function f(x: string): number {
+    return 0;
+}
+
+function g(x: "foo"): number;
+function g(x: string): number {
+    return 0;
+}
+
+let a = f;
+let b = g;
+
+a = b;
+b = a;

tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloadAssignability04.ts

@@ -0,0 +1,17 @@
+// @declaration: true
+
+function f(x: "foo"): number;
+function f(x: "foo"): number {
+    return 0;
+}
+
+function g(x: "foo"): number;
+function g(x: "foo"): number {
+    return 0;
+}
+
+let a = f;
+let b = g;
+
+a = b;
+b = a;

tests/cases/conformance/types/stringLiteral/stringLiteralTypesOverloadAssignability05.ts

@@ -0,0 +1,18 @@
+// @declaration: true
+
+function f(x: "foo"): number;
+function f(x: string): number;
+function f(x: string): number {
+    return 0;
+}
+
+function g(x: "foo"): number;
+function g(x: string): number {
+    return 0;
+}
+
+let a = f;
+let b = g;
+
+a = b;
+b = a;