Prefer using enum literal's own base type rather than enum's base type in comparison (#52703)

Author: jakebailey

src/compiler/checker.ts

@@ -23018,6 +23018,17 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return getCachedType(key) ?? setCachedType(key, mapType(type, getBaseTypeOfLiteralType));
     }
 
+    // This like getBaseTypeOfLiteralType, but instead treats enum literals as strings/numbers instead
+    // of returning their enum base type (which depends on the types of other literals in the enum).
+    function getBaseTypeOfLiteralTypeForComparison(type: Type): Type {
+        return type.flags & (TypeFlags.StringLiteral | TypeFlags.TemplateLiteral | TypeFlags.StringMapping) ? stringType :
+            type.flags & (TypeFlags.NumberLiteral | TypeFlags.Enum) ? numberType :
+            type.flags & TypeFlags.BigIntLiteral ? bigintType :
+            type.flags & TypeFlags.BooleanLiteral ? booleanType :
+            type.flags & TypeFlags.Union ? mapType(type, getBaseTypeOfLiteralTypeForComparison) :
+            type;
+    }
+
     function getWidenedLiteralType(type: Type): Type {
         return type.flags & TypeFlags.EnumLike && isFreshLiteralType(type) ? getBaseTypeOfEnumLikeType(type as LiteralType) :
             type.flags & TypeFlags.StringLiteral && isFreshLiteralType(type) ? stringType :
@@ -36481,8 +36492,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             case SyntaxKind.LessThanEqualsToken:
             case SyntaxKind.GreaterThanEqualsToken:
                 if (checkForDisallowedESSymbolOperand(operator)) {
-                    leftType = getBaseTypeOfLiteralType(checkNonNullType(leftType, left));
-                    rightType = getBaseTypeOfLiteralType(checkNonNullType(rightType, right));
+                    leftType = getBaseTypeOfLiteralTypeForComparison(checkNonNullType(leftType, left));
+                    rightType = getBaseTypeOfLiteralTypeForComparison(checkNonNullType(rightType, right));
                     reportOperatorErrorUnless((left, right) => {
                         if (isTypeAny(left) || isTypeAny(right)) {
                             return true;

tests/baselines/reference/comparisonOperatorWithNoRelationshipPrimitiveType.errors.txt

@@ -7,37 +7,37 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(18,14): error TS2367: This comparison appears to be unintentional because the types 'T' and 'U' have no overlap.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(19,14): error TS2367: This comparison appears to be unintentional because the types 'T' and 'U' have no overlap.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(23,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(26,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(26,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(31,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(34,16): error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(34,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(40,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(43,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(43,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(48,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(51,16): error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(51,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(57,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(60,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(60,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(65,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(68,16): error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(68,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(74,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(77,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(77,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(82,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(85,16): error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(85,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(91,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(94,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(94,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(99,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(102,16): error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(102,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(108,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(111,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(111,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(116,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(119,16): error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(119,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(125,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(128,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(128,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(133,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(136,16): error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(136,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(142,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(145,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(145,16): error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
 tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(150,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
-tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(153,16): error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts(153,16): error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
 
 
 ==== tests/cases/conformance/expressions/binaryOperators/comparisonOperator/comparisonOperatorWithNoRelationshipTypeParameter.ts (40 errors) ====
@@ -86,7 +86,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r1a4 = t < d;
         var r1a5 = t < e;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
         var r1a6 = t < f;
         var r1a7 = t < g;
 
@@ -98,7 +98,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r1b4 = d < t;
         var r1b5 = e < t;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+!!! error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
         var r1b6 = f < t;
         var r1b7 = g < t;
 
@@ -111,7 +111,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r2a4 = t < d;
         var r2a5 = t < e;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
         var r2a6 = t < f;
         var r2a7 = t < g;
 
@@ -123,7 +123,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r2b4 = d < t;
         var r2b5 = e < t;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+!!! error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
         var r2b6 = f < t;
         var r2b7 = g < t;
 
@@ -136,7 +136,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r3a4 = t < d;
         var r3a5 = t < e;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
         var r3a6 = t < f;
         var r3a7 = t < g;
 
@@ -148,7 +148,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r3b4 = d < t;
         var r3b5 = e < t;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+!!! error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
         var r3b6 = f < t;
         var r3b7 = g < t;
 
@@ -161,7 +161,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r4a4 = t < d;
         var r4a5 = t < e;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
         var r4a6 = t < f;
         var r4a7 = t < g;
 
@@ -173,7 +173,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r4b4 = d < t;
         var r4b5 = e < t;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+!!! error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
         var r4b6 = f < t;
         var r4b7 = g < t;
 
@@ -186,7 +186,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r5a4 = t < d;
         var r5a5 = t < e;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
         var r5a6 = t < f;
         var r5a7 = t < g;
 
@@ -198,7 +198,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r5b4 = d < t;
         var r5b5 = e < t;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+!!! error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
         var r5b6 = f < t;
         var r5b7 = g < t;
 
@@ -211,7 +211,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r6a4 = t < d;
         var r6a5 = t < e;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
         var r6a6 = t < f;
         var r6a7 = t < g;
 
@@ -223,7 +223,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r6b4 = d < t;
         var r6b5 = e < t;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+!!! error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
         var r6b6 = f < t;
         var r6b7 = g < t;
 
@@ -236,7 +236,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r7a4 = t < d;
         var r7a5 = t < e;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
         var r7a6 = t < f;
         var r7a7 = t < g;
 
@@ -248,7 +248,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r7b4 = d < t;
         var r7b5 = e < t;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+!!! error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
         var r7b6 = f < t;
         var r7b7 = g < t;
 
@@ -261,7 +261,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r8a4 = t < d;
         var r8a5 = t < e;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'E'.
+!!! error TS2365: Operator '<' cannot be applied to types 'T' and 'number'.
         var r8a6 = t < f;
         var r8a7 = t < g;
 
@@ -273,7 +273,7 @@ tests/cases/conformance/expressions/binaryOperators/comparisonOperator/compariso
         var r8b4 = d < t;
         var r8b5 = e < t;
                    ~~~~~
-!!! error TS2365: Operator '<' cannot be applied to types 'E' and 'T'.
+!!! error TS2365: Operator '<' cannot be applied to types 'number' and 'T'.
         var r8b6 = f < t;
         var r8b7 = g < t;
     }

tests/baselines/reference/comparisonOperatorWithNoRelationshipTypeParameter.errors.txt

@@ -0,0 +1,61 @@
+//// [mixedTypeEnumComparison.ts]
+const enum E {
+    S1 = "foo",
+    S2 = "bar",
+
+    N1 = 1000,
+    N2 = 25,
+}
+
+declare var someNumber: number
+
+if (someNumber > E.N2) {
+    someNumber = E.N2;
+}
+
+declare const unionOfEnum: E.N1 | E.N2;
+
+if (someNumber > unionOfEnum) {
+    someNumber = E.N2;
+}
+
+declare var someString: string
+
+if (someString > E.S1) {
+    someString = E.S2;
+}
+
+
+declare function someValue(): number;
+
+enum E2 {
+    S1 = "foo",
+    N1 = 1000,
+    C1 = someValue(),
+}
+
+someString > E2.S1;
+someNumber > E2.N1;
+someNumber > E2.C1;
+
+
+//// [mixedTypeEnumComparison.js]
+"use strict";
+if (someNumber > 25 /* E.N2 */) {
+    someNumber = 25 /* E.N2 */;
+}
+if (someNumber > unionOfEnum) {
+    someNumber = 25 /* E.N2 */;
+}
+if (someString > "foo" /* E.S1 */) {
+    someString = "bar" /* E.S2 */;
+}
+var E2;
+(function (E2) {
+    E2["S1"] = "foo";
+    E2[E2["N1"] = 1000] = "N1";
+    E2[E2["C1"] = someValue()] = "C1";
+})(E2 || (E2 = {}));
+someString > E2.S1;
+someNumber > E2.N1;
+someNumber > E2.C1;