Merge pull request #12538 from Microsoft/fixExhaustiveSwitchCheck

Fix exhaustive switch check

Author: ahejlsberg

src/compiler/checker.ts

@@ -13850,7 +13850,7 @@ namespace ts {
             if (!switchTypes.length) {
                 return false;
             }
-            return eachTypeContainedIn(type, switchTypes);
+            return eachTypeContainedIn(mapType(type, getRegularTypeOfLiteralType), switchTypes);
         }
 
         function functionHasImplicitReturn(func: FunctionLikeDeclaration) {

tests/baselines/reference/exhaustiveSwitchWithWideningLiteralTypes.js

@@ -0,0 +1,39 @@
+//// [exhaustiveSwitchWithWideningLiteralTypes.ts]
+
+// Repro from #12529
+
+class A {
+    readonly kind = "A"; // (property) A.kind: "A"
+}
+
+class B {
+    readonly kind = "B"; // (property) B.kind: "B"
+}
+
+function f(value: A | B): number {
+    switch(value.kind) {
+        case "A": return 0;
+        case "B": return 1;
+    }
+}
+
+//// [exhaustiveSwitchWithWideningLiteralTypes.js]
+// Repro from #12529
+var A = (function () {
+    function A() {
+        this.kind = "A"; // (property) A.kind: "A"
+    }
+    return A;
+}());
+var B = (function () {
+    function B() {
+        this.kind = "B"; // (property) B.kind: "B"
+    }
+    return B;
+}());
+function f(value) {
+    switch (value.kind) {
+        case "A": return 0;
+        case "B": return 1;
+    }
+}

tests/baselines/reference/exhaustiveSwitchWithWideningLiteralTypes.symbols

@@ -0,0 +1,33 @@
+=== tests/cases/compiler/exhaustiveSwitchWithWideningLiteralTypes.ts ===
+
+// Repro from #12529
+
+class A {
+>A : Symbol(A, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 0, 0))
+
+    readonly kind = "A"; // (property) A.kind: "A"
+>kind : Symbol(A.kind, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 3, 9))
+}
+
+class B {
+>B : Symbol(B, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 5, 1))
+
+    readonly kind = "B"; // (property) B.kind: "B"
+>kind : Symbol(B.kind, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 7, 9))
+}
+
+function f(value: A | B): number {
+>f : Symbol(f, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 9, 1))
+>value : Symbol(value, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 11, 11))
+>A : Symbol(A, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 0, 0))
+>B : Symbol(B, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 5, 1))
+
+    switch(value.kind) {
+>value.kind : Symbol(kind, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 3, 9), Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 7, 9))
+>value : Symbol(value, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 11, 11))
+>kind : Symbol(kind, Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 3, 9), Decl(exhaustiveSwitchWithWideningLiteralTypes.ts, 7, 9))
+
+        case "A": return 0;
+        case "B": return 1;
+    }
+}

tests/baselines/reference/exhaustiveSwitchWithWideningLiteralTypes.types

@@ -0,0 +1,40 @@
+=== tests/cases/compiler/exhaustiveSwitchWithWideningLiteralTypes.ts ===
+
+// Repro from #12529
+
+class A {
+>A : A
+
+    readonly kind = "A"; // (property) A.kind: "A"
+>kind : "A"
+>"A" : "A"
+}
+
+class B {
+>B : B
+
+    readonly kind = "B"; // (property) B.kind: "B"
+>kind : "B"
+>"B" : "B"
+}
+
+function f(value: A | B): number {
+>f : (value: A | B) => number
+>value : A | B
+>A : A
+>B : B
+
+    switch(value.kind) {
+>value.kind : "A" | "B"
+>value : A | B
+>kind : "A" | "B"
+
+        case "A": return 0;
+>"A" : "A"
+>0 : 0
+
+        case "B": return 1;
+>"B" : "B"
+>1 : 1
+    }
+}

tests/cases/compiler/exhaustiveSwitchWithWideningLiteralTypes.ts

@@ -0,0 +1,18 @@
+// @strictNullChecks: true
+
+// Repro from #12529
+
+class A {
+    readonly kind = "A"; // (property) A.kind: "A"
+}
+
+class B {
+    readonly kind = "B"; // (property) B.kind: "B"
+}
+
+function f(value: A | B): number {
+    switch(value.kind) {
+        case "A": return 0;
+        case "B": return 1;
+    }
+}