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Merged
merged 5 commits into from
Feb 16, 2023
Merged

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

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11ff2a5
Add test
jakebailey Feb 9, 2023
d7cefaf
Prefer using enum literal's own base type rather than enum's base typ…
jakebailey Feb 9, 2023
e808551
Fix unions
jakebailey Feb 9, 2023
ce188e2
PR feedback
jakebailey Feb 16, 2023
31a6171
Reword comment
jakebailey Feb 16, 2023
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21 changes: 19 additions & 2 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -22983,6 +22983,23 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
return getCachedType(key) ?? setCachedType(key, mapType(type, getBaseTypeOfLiteralType));
}

// This is the same as getBaseTypeOfLiteralType, but checks EnumLiteral last so we get
// a specific literal's base type rather than the enum's base type.
function getBaseTypeOfLiteralTypeForComparison(type: Type): Type {
return type.flags & (TypeFlags.StringLiteral | TypeFlags.TemplateLiteral | TypeFlags.StringMapping) ? stringType :
type.flags & TypeFlags.NumberLiteral ? numberType :
type.flags & TypeFlags.BigIntLiteral ? bigintType :
type.flags & TypeFlags.BooleanLiteral ? booleanType :
type.flags & TypeFlags.EnumLiteral ? getBaseTypeOfEnumLiteralType(type as LiteralType) :
type.flags & TypeFlags.Union ? getBaseTypeOfLiteralTypeUnionForComparison(type as UnionType) :
type;
}

function getBaseTypeOfLiteralTypeUnionForComparison(type: UnionType) {
const key = `BC${getTypeId(type)}`;
return getCachedType(key) ?? setCachedType(key, mapType(type, getBaseTypeOfLiteralTypeForComparison));
}

function getWidenedLiteralType(type: Type): Type {
return type.flags & TypeFlags.EnumLiteral && isFreshLiteralType(type) ? getBaseTypeOfEnumLiteralType(type as LiteralType) :
type.flags & TypeFlags.StringLiteral && isFreshLiteralType(type) ? stringType :
Expand Down Expand Up @@ -36423,8 +36440,8 @@ 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));
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@jakebailey jakebailey Feb 9, 2023 •
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I suspect this isn't the only case; the AmpersandAmpersandToken block below also uses the old function. But, changing that produces an... odd result:

>rf6 : 0 | E.b | E.c
>a6 && a6 : 0 | E.b | E.c

Because the result is actually used for the output, whereas this comparison block always gives back bool and so the unions would not be visible.

rightType = getBaseTypeOfLiteralTypeForComparison(checkNonNullType(rightType, right));
reportOperatorErrorUnless((left, right) => {
if (isTypeAny(left) || isTypeAny(right)) {
return true;
Expand Down
40 changes: 40 additions & 0 deletions tests/baselines/reference/mixedTypeEnumComparison.js
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@@ -0,0 +1,40 @@
//// [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;
}



//// [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 */;
}
68 changes: 68 additions & 0 deletions tests/baselines/reference/mixedTypeEnumComparison.symbols
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@@ -0,0 +1,68 @@
=== tests/cases/compiler/mixedTypeEnumComparison.ts ===
const enum E {
>E : Symbol(E, Decl(mixedTypeEnumComparison.ts, 0, 0))

S1 = "foo",
>S1 : Symbol(E.S1, Decl(mixedTypeEnumComparison.ts, 0, 14))

S2 = "bar",
>S2 : Symbol(E.S2, Decl(mixedTypeEnumComparison.ts, 1, 15))

N1 = 1000,
>N1 : Symbol(E.N1, Decl(mixedTypeEnumComparison.ts, 2, 15))

N2 = 25,
>N2 : Symbol(E.N2, Decl(mixedTypeEnumComparison.ts, 4, 14))
}

declare var someNumber: number
>someNumber : Symbol(someNumber, Decl(mixedTypeEnumComparison.ts, 8, 11))

if (someNumber > E.N2) {
>someNumber : Symbol(someNumber, Decl(mixedTypeEnumComparison.ts, 8, 11))
>E.N2 : Symbol(E.N2, Decl(mixedTypeEnumComparison.ts, 4, 14))
>E : Symbol(E, Decl(mixedTypeEnumComparison.ts, 0, 0))
>N2 : Symbol(E.N2, Decl(mixedTypeEnumComparison.ts, 4, 14))

someNumber = E.N2;
>someNumber : Symbol(someNumber, Decl(mixedTypeEnumComparison.ts, 8, 11))
>E.N2 : Symbol(E.N2, Decl(mixedTypeEnumComparison.ts, 4, 14))
>E : Symbol(E, Decl(mixedTypeEnumComparison.ts, 0, 0))
>N2 : Symbol(E.N2, Decl(mixedTypeEnumComparison.ts, 4, 14))
}

declare const unionOfEnum: E.N1 | E.N2;
>unionOfEnum : Symbol(unionOfEnum, Decl(mixedTypeEnumComparison.ts, 14, 13))
>E : Symbol(E, Decl(mixedTypeEnumComparison.ts, 0, 0))
>N1 : Symbol(E.N1, Decl(mixedTypeEnumComparison.ts, 2, 15))
>E : Symbol(E, Decl(mixedTypeEnumComparison.ts, 0, 0))
>N2 : Symbol(E.N2, Decl(mixedTypeEnumComparison.ts, 4, 14))

if (someNumber > unionOfEnum) {
>someNumber : Symbol(someNumber, Decl(mixedTypeEnumComparison.ts, 8, 11))
>unionOfEnum : Symbol(unionOfEnum, Decl(mixedTypeEnumComparison.ts, 14, 13))

someNumber = E.N2;
>someNumber : Symbol(someNumber, Decl(mixedTypeEnumComparison.ts, 8, 11))
>E.N2 : Symbol(E.N2, Decl(mixedTypeEnumComparison.ts, 4, 14))
>E : Symbol(E, Decl(mixedTypeEnumComparison.ts, 0, 0))
>N2 : Symbol(E.N2, Decl(mixedTypeEnumComparison.ts, 4, 14))
}

declare var someString: string
>someString : Symbol(someString, Decl(mixedTypeEnumComparison.ts, 20, 11))

if (someString > E.S1) {
>someString : Symbol(someString, Decl(mixedTypeEnumComparison.ts, 20, 11))
>E.S1 : Symbol(E.S1, Decl(mixedTypeEnumComparison.ts, 0, 14))
>E : Symbol(E, Decl(mixedTypeEnumComparison.ts, 0, 0))
>S1 : Symbol(E.S1, Decl(mixedTypeEnumComparison.ts, 0, 14))

someString = E.S2;
>someString : Symbol(someString, Decl(mixedTypeEnumComparison.ts, 20, 11))
>E.S2 : Symbol(E.S2, Decl(mixedTypeEnumComparison.ts, 1, 15))
>E : Symbol(E, Decl(mixedTypeEnumComparison.ts, 0, 0))
>S2 : Symbol(E.S2, Decl(mixedTypeEnumComparison.ts, 1, 15))
}


76 changes: 76 additions & 0 deletions tests/baselines/reference/mixedTypeEnumComparison.types
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@@ -0,0 +1,76 @@
=== tests/cases/compiler/mixedTypeEnumComparison.ts ===
const enum E {
>E : E

S1 = "foo",
>S1 : E.S1
>"foo" : "foo"

S2 = "bar",
>S2 : E.S2
>"bar" : "bar"

N1 = 1000,
>N1 : E.N1
>1000 : 1000

N2 = 25,
>N2 : E.N2
>25 : 25
}

declare var someNumber: number
>someNumber : number

if (someNumber > E.N2) {
>someNumber > E.N2 : boolean
>someNumber : number
>E.N2 : E.N2
>E : typeof E
>N2 : E.N2

someNumber = E.N2;
>someNumber = E.N2 : E.N2
>someNumber : number
>E.N2 : E.N2
>E : typeof E
>N2 : E.N2
}

declare const unionOfEnum: E.N1 | E.N2;
>unionOfEnum : E.N1 | E.N2
>E : any
>E : any

if (someNumber > unionOfEnum) {
>someNumber > unionOfEnum : boolean
>someNumber : number
>unionOfEnum : E.N1 | E.N2

someNumber = E.N2;
>someNumber = E.N2 : E.N2
>someNumber : number
>E.N2 : E.N2
>E : typeof E
>N2 : E.N2
}

declare var someString: string
>someString : string

if (someString > E.S1) {
>someString > E.S1 : boolean
>someString : string
>E.S1 : E.S1
>E : typeof E
>S1 : E.S1

someString = E.S2;
>someString = E.S2 : E.S2
>someString : string
>E.S2 : E.S2
>E : typeof E
>S2 : E.S2
}


28 changes: 28 additions & 0 deletions tests/cases/compiler/mixedTypeEnumComparison.ts
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@@ -0,0 +1,28 @@
// @strict: true

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;
}