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[experiment] Bail out early in union production if too many literals/templates #59705

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[experiment] Bail out early in union production if too many literals/templates #59705

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0d93b47
[experiment] Bail out early in union production if too many literals/…
jakebailey Aug 21, 2024
5ae71e6
Baseline because why not
jakebailey Aug 21, 2024
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15 changes: 13 additions & 2 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -17668,9 +17668,16 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}
}

function removeStringLiteralsMatchedByTemplateLiterals(types: Type[]) {
function removeStringLiteralsMatchedByTemplateLiterals(types: Type[]): Type[] | undefined {
const templates = filter(types, isPatternLiteralType) as (TemplateLiteralType | StringMappingType)[];
if (templates.length) {
const estimatedCount = templates.length * countWhere(types, t => !!(t.flags & TypeFlags.StringLiteral));
if (estimatedCount > 1000000) {
tracing?.instant(tracing.Phase.CheckTypes, "removeStringLiteralsMatchedByTemplateLiterals_DepthLimit", { typeIds: types.map(t => t.id) });
error(currentNode, Diagnostics.Expression_produces_a_union_type_that_is_too_complex_to_represent);
return undefined;
}

let i = types.length;
while (i > 0) {
i--;
Expand All @@ -17680,6 +17687,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}
}
}
return types;
}

function isTypeMatchedByTemplateLiteralOrStringMapping(type: Type, template: TemplateLiteralType | StringMappingType) {
Expand Down Expand Up @@ -17804,7 +17812,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
removeRedundantLiteralTypes(typeSet, includes, !!(unionReduction & UnionReduction.Subtype));
}
if (includes & TypeFlags.StringLiteral && includes & (TypeFlags.TemplateLiteral | TypeFlags.StringMapping)) {
removeStringLiteralsMatchedByTemplateLiterals(typeSet);
typeSet = removeStringLiteralsMatchedByTemplateLiterals(typeSet);
if (!typeSet) {
return errorType;
}
}
if (includes & TypeFlags.IncludesConstrainedTypeVariable) {
removeConstrainedTypeVariables(typeSet);
Expand Down
5 changes: 4 additions & 1 deletion tests/baselines/reference/templateLiteralTypes1.errors.txt
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Expand Up @@ -6,10 +6,11 @@ templateLiteralTypes1.ts(165,15): error TS1338: 'infer' declarations are only pe
templateLiteralTypes1.ts(197,16): error TS2590: Expression produces a union type that is too complex to represent.
templateLiteralTypes1.ts(201,16): error TS2590: Expression produces a union type that is too complex to represent.
templateLiteralTypes1.ts(205,16): error TS2590: Expression produces a union type that is too complex to represent.
templateLiteralTypes1.ts(251,7): error TS2590: Expression produces a union type that is too complex to represent.
templateLiteralTypes1.ts(252,7): error TS2590: Expression produces a union type that is too complex to represent.


==== templateLiteralTypes1.ts (7 errors) ====
==== templateLiteralTypes1.ts (8 errors) ====
// Template types example from #12754

const createScopedActionType = <S extends string>(scope: S) => <T extends string>(type: T) => `${scope}/${type}` as `${S}/${T}`;
Expand Down Expand Up @@ -276,6 +277,8 @@ templateLiteralTypes1.ts(252,7): error TS2590: Expression produces a union type
export type SpacingShorthand =
| `${Spacing} ${Spacing}`
| `${Spacing} ${Spacing} ${Spacing}`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
!!! error TS2590: Expression produces a union type that is too complex to represent.
| `${Spacing} ${Spacing} ${Spacing} ${Spacing}`;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
!!! error TS2590: Expression produces a union type that is too complex to represent.
Expand Down