Fix comparable in switch

src/compiler/checker.ts

@@ -16883,6 +16883,7 @@ namespace ts {
             let hasDuplicateDefaultClause = false;
 
             const expressionType = checkExpression(node.expression);
+            const expressionIsLiteral = isLiteralType(expressionType);
             forEach(node.caseBlock.clauses, clause => {
                 // Grammar check for duplicate default clauses, skip if we already report duplicate default clause
                 if (clause.kind === SyntaxKind.DefaultClause && !hasDuplicateDefaultClause) {
@@ -16903,10 +16904,16 @@ namespace ts {
                     // TypeScript 1.0 spec (April 2014): 5.9
                     // In a 'switch' statement, each 'case' expression must be of a type that is comparable
                     // to or from the type of the 'switch' expression.
-                    const caseType = checkExpression(caseClause.expression);
-                    if (!isTypeEqualityComparableTo(expressionType, caseType)) {
+                    let caseType = checkExpression(caseClause.expression);
+                    const caseIsLiteral = isLiteralType(caseType);
+                    let comparedExpressionType = expressionType;
+                    if (!caseIsLiteral || !expressionIsLiteral) {
+                        caseType = caseIsLiteral ? getBaseTypeOfLiteralType(caseType) : caseType;
+                        comparedExpressionType = getBaseTypeOfLiteralType(expressionType);
+                    }
+                    if (!isTypeEqualityComparableTo(comparedExpressionType, caseType)) {
                         // expressionType is not comparable to caseType, try the reversed check and report errors if it fails
-                        checkTypeComparableTo(caseType, expressionType, caseClause.expression, /*headMessage*/ undefined);
+                        checkTypeComparableTo(caseType, comparedExpressionType, caseClause.expression, /*headMessage*/ undefined);
                     }
                 }
                 forEach(clause.statements, checkSourceElement);

tests/baselines/reference/switchAssignmentCompat.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/compiler/switchAssignmentCompat.ts(4,10): error TS2678: Type 'typeof Foo' is not comparable to type '0'.
+tests/cases/compiler/switchAssignmentCompat.ts(4,10): error TS2678: Type 'typeof Foo' is not comparable to type 'number'.
 
 
 ==== tests/cases/compiler/switchAssignmentCompat.ts (1 errors) ====
@@ -7,6 +7,6 @@ tests/cases/compiler/switchAssignmentCompat.ts(4,10): error TS2678: Type 'typeof
     switch (0) {
         case Foo: break; // Error expected
              ~~~
-!!! error TS2678: Type 'typeof Foo' is not comparable to type '0'.
+!!! error TS2678: Type 'typeof Foo' is not comparable to type 'number'.
     }
 

tests/baselines/reference/switchCaseCircularRefeference.errors.txt

@@ -1,6 +1,5 @@
-tests/cases/compiler/switchCaseCircularRefeference.ts(5,10): error TS2678: Type '{ a: "A"; b: any; } | { a: "C"; e: any; }' is not comparable to type '"A" | "C"'.
-  Type '{ a: "C"; e: any; }' is not comparable to type '"A" | "C"'.
-    Type '{ a: "C"; e: any; }' is not comparable to type '"C"'.
+tests/cases/compiler/switchCaseCircularRefeference.ts(5,10): error TS2678: Type '{ a: "A"; b: any; } | { a: "C"; e: any; }' is not comparable to type 'string'.
+  Type '{ a: "C"; e: any; }' is not comparable to type 'string'.
 
 
 ==== tests/cases/compiler/switchCaseCircularRefeference.ts (1 errors) ====
@@ -10,9 +9,8 @@ tests/cases/compiler/switchCaseCircularRefeference.ts(5,10): error TS2678: Type
         switch (x.a) {
         case x:
              ~
-!!! error TS2678: Type '{ a: "A"; b: any; } | { a: "C"; e: any; }' is not comparable to type '"A" | "C"'.
-!!! error TS2678:   Type '{ a: "C"; e: any; }' is not comparable to type '"A" | "C"'.
-!!! error TS2678:     Type '{ a: "C"; e: any; }' is not comparable to type '"C"'.
+!!! error TS2678: Type '{ a: "A"; b: any; } | { a: "C"; e: any; }' is not comparable to type 'string'.
+!!! error TS2678:   Type '{ a: "C"; e: any; }' is not comparable to type 'string'.
             break;
         }
     }

tests/baselines/reference/switchCasesExpressionTypeMismatch.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/compiler/switchCasesExpressionTypeMismatch.ts(4,10): error TS2678: Type 'typeof Foo' is not comparable to type '0'.
+tests/cases/compiler/switchCasesExpressionTypeMismatch.ts(4,10): error TS2678: Type 'typeof Foo' is not comparable to type 'number'.
 tests/cases/compiler/switchCasesExpressionTypeMismatch.ts(5,10): error TS2678: Type '"sss"' is not comparable to type '0'.
 tests/cases/compiler/switchCasesExpressionTypeMismatch.ts(6,10): error TS2678: Type '123' is not comparable to type '0'.
 tests/cases/compiler/switchCasesExpressionTypeMismatch.ts(7,10): error TS2678: Type 'true' is not comparable to type '0'.
@@ -10,11 +10,11 @@ tests/cases/compiler/switchCasesExpressionTypeMismatch.ts(7,10): error TS2678: T
     switch (0) {
         case Foo: break;    // Error
              ~~~
-!!! error TS2678: Type 'typeof Foo' is not comparable to type '0'.
+!!! error TS2678: Type 'typeof Foo' is not comparable to type 'number'.
         case "sss": break;  // Error
              ~~~~~
 !!! error TS2678: Type '"sss"' is not comparable to type '0'.
-        case 123: break;    // No Error
+        case 123: break;    // Error
              ~~~
 !!! error TS2678: Type '123' is not comparable to type '0'.
         case true: break;   // Error
@@ -30,4 +30,5 @@ tests/cases/compiler/switchCasesExpressionTypeMismatch.ts(7,10): error TS2678: T
         case "sss": break;
         case 123: break;
         case true: break;
-    }
+    }
+

tests/baselines/reference/switchCasesExpressionTypeMismatch.js

@@ -4,7 +4,7 @@ class Foo { }
 switch (0) {
     case Foo: break;    // Error
     case "sss": break;  // Error
-    case 123: break;    // No Error
+    case 123: break;    // Error
     case true: break;   // Error
 }
 
@@ -16,7 +16,8 @@ switch (s) {
     case "sss": break;
     case 123: break;
     case true: break;
-}
+}
+
 
 //// [switchCasesExpressionTypeMismatch.js]
 var Foo = (function () {
@@ -27,7 +28,7 @@ var Foo = (function () {
 switch (0) {
     case Foo: break; // Error
     case "sss": break; // Error
-    case 123: break; // No Error
+    case 123: break; // Error
     case true: break; // Error
 }
 var s = 0;

tests/baselines/reference/switchComparableCompatForBrands.js

@@ -0,0 +1,29 @@
+//// [switchComparableCompatForBrands.ts]
+class MyBrand
+{
+    private _a: number;
+}
+
+function test(strInput: string & MyBrand) {
+    switch(strInput)
+    {
+        case "a":
+        return 1;
+    }
+    return 0;
+}
+
+
+//// [switchComparableCompatForBrands.js]
+var MyBrand = (function () {
+    function MyBrand() {
+    }
+    return MyBrand;
+}());
+function test(strInput) {
+    switch (strInput) {
+        case "a":
+            return 1;
+    }
+    return 0;
+}

tests/baselines/reference/switchComparableCompatForBrands.symbols

@@ -0,0 +1,22 @@
+=== tests/cases/compiler/switchComparableCompatForBrands.ts ===
+class MyBrand
+>MyBrand : Symbol(MyBrand, Decl(switchComparableCompatForBrands.ts, 0, 0))
+{
+    private _a: number;
+>_a : Symbol(MyBrand._a, Decl(switchComparableCompatForBrands.ts, 1, 1))
+}
+
+function test(strInput: string & MyBrand) {
+>test : Symbol(test, Decl(switchComparableCompatForBrands.ts, 3, 1))
+>strInput : Symbol(strInput, Decl(switchComparableCompatForBrands.ts, 5, 14))
+>MyBrand : Symbol(MyBrand, Decl(switchComparableCompatForBrands.ts, 0, 0))
+
+    switch(strInput)
+>strInput : Symbol(strInput, Decl(switchComparableCompatForBrands.ts, 5, 14))
+    {
+        case "a":
+        return 1;
+    }
+    return 0;
+}
+

tests/baselines/reference/switchComparableCompatForBrands.types

@@ -0,0 +1,26 @@
+=== tests/cases/compiler/switchComparableCompatForBrands.ts ===
+class MyBrand
+>MyBrand : MyBrand
+{
+    private _a: number;
+>_a : number
+}
+
+function test(strInput: string & MyBrand) {
+>test : (strInput: string & MyBrand) => 1 | 0
+>strInput : string & MyBrand
+>MyBrand : MyBrand
+
+    switch(strInput)
+>strInput : string & MyBrand
+    {
+        case "a":
+>"a" : "a"
+
+        return 1;
+>1 : 1
+    }
+    return 0;
+>0 : 0
+}
+

tests/cases/compiler/switchCasesExpressionTypeMismatch.ts

@@ -3,7 +3,7 @@ class Foo { }
 switch (0) {
     case Foo: break;    // Error
     case "sss": break;  // Error
-    case 123: break;    // No Error
+    case 123: break;    // Error
     case true: break;   // Error
 }
 
@@ -15,4 +15,4 @@ switch (s) {
     case "sss": break;
     case 123: break;
     case true: break;
-}
+}

tests/cases/compiler/switchComparableCompatForBrands.ts

@@ -0,0 +1,13 @@
+class MyBrand
+{
+    private _a: number;
+}
+
+function test(strInput: string & MyBrand) {
+    switch(strInput)
+    {
+        case "a":
+        return 1;
+    }
+    return 0;
+}