diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts index 1be2bbe8d74f4..4ac2e391f1975 100644 --- a/src/compiler/checker.ts +++ b/src/compiler/checker.ts @@ -18361,31 +18361,6 @@ namespace ts { } } - if (!result && source.flags & (TypeFlags.Intersection | TypeFlags.TypeParameter)) { - // The combined constraint of an intersection type is the intersection of the constraints of - // the constituents. When an intersection type contains instantiable types with union type - // constraints, there are situations where we need to examine the combined constraint. One is - // when the target is a union type. Another is when the intersection contains types belonging - // to one of the disjoint domains. For example, given type variables T and U, each with the - // constraint 'string | number', the combined constraint of 'T & U' is 'string | number' and - // we need to check this constraint against a union on the target side. Also, given a type - // variable V constrained to 'string | number', 'V & number' has a combined constraint of - // 'string & number | number & number' which reduces to just 'number'. - // This also handles type parameters, as a type parameter with a union constraint compared against a union - // needs to have its constraint hoisted into an intersection with said type parameter, this way - // the type param can be compared with itself in the target (with the influence of its constraint to match other parts) - // For example, if `T extends 1 | 2` and `U extends 2 | 3` and we compare `T & U` to `T & U & (1 | 2 | 3)` - const constraint = getEffectiveConstraintOfIntersection(source.flags & TypeFlags.Intersection ? (source as IntersectionType).types: [source], !!(target.flags & TypeFlags.Union)); - if (constraint && (source.flags & TypeFlags.Intersection || target.flags & TypeFlags.Union)) { - if (everyType(constraint, c => c !== source)) { // Skip comparison if expansion contains the source itself - // TODO: Stack errors so we get a pyramid for the "normal" comparison above, _and_ a second for this - if (result = isRelatedTo(constraint, target, RecursionFlags.Source, /*reportErrors*/ false, /*headMessage*/ undefined, intersectionState)) { - resetErrorInfo(saveErrorInfo); - } - } - } - } - // For certain combinations involving intersections and optional, excess, or mismatched properties we need // an extra property check where the intersection is viewed as a single object. The following are motivating // examples that all should be errors, but aren't without this extra property check: @@ -18970,17 +18945,44 @@ namespace ts { } } else if (sourceFlags & TypeFlags.UnionOrIntersection || targetFlags & TypeFlags.UnionOrIntersection) { - result = unionOrIntersectionRelatedTo(source, target, reportErrors, intersectionState); + if (result = unionOrIntersectionRelatedTo(source, target, reportErrors, intersectionState)) { + return result; + } + if (source.flags & TypeFlags.Intersection || source.flags & TypeFlags.TypeParameter && target.flags & TypeFlags.Union) { + // (T extends 1 | 2) & 1 <=> 1 + // (T extends 1 | 2) <=> T & 1 | T & 2 + // The combined constraint of an intersection type is the intersection of the constraints of + // the constituents. When an intersection type contains instantiable types with union type + // constraints, there are situations where we need to examine the combined constraint. One is + // when the target is a union type. Another is when the intersection contains types belonging + // to one of the disjoint domains. For example, given type variables T and U, each with the + // constraint 'string | number', the combined constraint of 'T & U' is 'string | number' and + // we need to check this constraint against a union on the target side. Also, given a type + // variable V constrained to 'string | number', 'V & number' has a combined constraint of + // 'string & number | number & number' which reduces to just 'number'. + // This also handles type parameters, as a type parameter with a union constraint compared against a union + // needs to have its constraint hoisted into an intersection with said type parameter, this way + // the type param can be compared with itself in the target (with the influence of its constraint to match other parts) + // For example, if `T extends 1 | 2` and `U extends 2 | 3` and we compare `T & U` to `T & U & (1 | 2 | 3)` + const constraint = getEffectiveConstraintOfIntersection(source.flags & TypeFlags.Intersection ? (source as IntersectionType).types: [source], !!(target.flags & TypeFlags.Union)); + if (constraint && everyType(constraint, c => c !== source)) { // Skip comparison if expansion contains the source itself + // TODO: Stack errors so we get a pyramid for the "normal" comparison above, _and_ a second for this + if (result = isRelatedTo(constraint, target, RecursionFlags.Source, /*reportErrors*/ false, /*headMessage*/ undefined, intersectionState)) { + resetErrorInfo(saveErrorInfo); + return result; + } + } + } // The ordered decomposition above doesn't handle all cases. Specifically, we also need to handle: // Source is instantiable (e.g. source has union or intersection constraint). // Source is an object, target is a union (e.g. { a, b: boolean } <=> { a, b: true } | { a, b: false }). // Source is an intersection, target is an object (e.g. { a } & { b } <=> { a, b }). // Source is an intersection, target is a union (e.g. { a } & { b: boolean } <=> { a, b: true } | { a, b: false }). // Source is an intersection, target instantiable (e.g. string & { tag } <=> T["a"] constrained to string & { tag }). - if (result || !(sourceFlags & TypeFlags.Instantiable || + if (!(sourceFlags & TypeFlags.Instantiable || sourceFlags & TypeFlags.Object && targetFlags & TypeFlags.Union || sourceFlags & TypeFlags.Intersection && targetFlags & (TypeFlags.Object | TypeFlags.Union | TypeFlags.Instantiable))) { - return result; + return Ternary.False; } }