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Improve logic that determines when to resolve conditional types

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This commit is contained in:
Anders Hejlsberg
2019-01-09 16:10:28 -08:00
parent 4a0bc59f77
commit 70148a4b55
2 changed files with 71 additions and 67 deletions
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134
src/compiler/checker.ts
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@@ -444,10 +444,10 @@ namespace ts {
const circularConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
const resolvingDefaultType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
const markerSuperType = <TypeParameter>createType(TypeFlags.TypeParameter);
const markerSubType = <TypeParameter>createType(TypeFlags.TypeParameter);
const markerSuperType = createTypeParameter();
const markerSubType = createTypeParameter();
markerSubType.constraint = markerSuperType;
const markerOtherType = <TypeParameter>createType(TypeFlags.TypeParameter);
const markerOtherType = createTypeParameter();
const noTypePredicate = createIdentifierTypePredicate("<<unresolved>>", 0, anyType);
@@ -663,7 +663,6 @@ namespace ts {
const subtypeRelation = createMap<RelationComparisonResult>();
const assignableRelation = createMap<RelationComparisonResult>();
const definitelyAssignableRelation = createMap<RelationComparisonResult>();
const comparableRelation = createMap<RelationComparisonResult>();
const identityRelation = createMap<RelationComparisonResult>();
const enumRelation = createMap<RelationComparisonResult>();
@@ -2745,6 +2744,12 @@ namespace ts {
return getUnionType(arrayFrom(typeofEQFacts.keys(), getLiteralType));
}
function createTypeParameter(symbol?: Symbol) {
const type = <TypeParameter>createType(TypeFlags.TypeParameter);
if (symbol) type.symbol = symbol;
return type;
}
// A reserved member name starts with two underscores, but the third character cannot be an underscore
// or the @ symbol. A third underscore indicates an escaped form of an identifer that started
// with at least two underscores. The @ character indicates that the name is denoted by a well known ES
@@ -6085,9 +6090,8 @@ namespace ts {
(<GenericType>type).instantiations.set(getTypeListId(type.typeParameters), <GenericType>type);
(<GenericType>type).target = <GenericType>type;
(<GenericType>type).typeArguments = type.typeParameters;
type.thisType = <TypeParameter>createType(TypeFlags.TypeParameter);
type.thisType = createTypeParameter(symbol);
type.thisType.isThisType = true;
type.thisType.symbol = symbol;
type.thisType.constraint = type;
}
}
@@ -6228,20 +6232,12 @@ namespace ts {
function getDeclaredTypeOfTypeParameter(symbol: Symbol): TypeParameter {
const links = getSymbolLinks(symbol);
if (!links.declaredType) {
const type = <TypeParameter>createType(TypeFlags.TypeParameter);
type.symbol = symbol;
links.declaredType = type;
}
return <TypeParameter>links.declaredType;
return links.declaredType || (links.declaredType = createTypeParameter(symbol));
}
function getDeclaredTypeOfAlias(symbol: Symbol): Type {
const links = getSymbolLinks(symbol);
if (!links.declaredType) {
links.declaredType = getDeclaredTypeOfSymbol(resolveAlias(symbol));
}
return links.declaredType;
return links.declaredType || (links.declaredType = getDeclaredTypeOfSymbol(resolveAlias(symbol)));
}
function getDeclaredTypeOfSymbol(symbol: Symbol): Type {
@@ -7413,7 +7409,7 @@ namespace ts {
if (type.root.isDistributive) {
const simplified = getSimplifiedType(type.checkType);
const constraint = simplified === type.checkType ? getConstraintOfType(simplified) : simplified;
if (constraint) {
if (constraint && constraint !== type.checkType) {
const mapper = makeUnaryTypeMapper(type.root.checkType, constraint);
const instantiated = getConditionalTypeInstantiation(type, combineTypeMappers(mapper, type.mapper));
if (!(instantiated.flags & TypeFlags.Never)) {
@@ -9049,7 +9045,7 @@ namespace ts {
if (arity) {
typeParameters = new Array(arity);
for (let i = 0; i < arity; i++) {
const typeParameter = typeParameters[i] = <TypeParameter>createType(TypeFlags.TypeParameter);
const typeParameter = typeParameters[i] = createTypeParameter();
if (i < maxLength) {
const property = createSymbol(SymbolFlags.Property | (i >= minLength ? SymbolFlags.Optional : 0), "" + i as __String);
property.type = typeParameter;
@@ -9070,7 +9066,7 @@ namespace ts {
type.instantiations.set(getTypeListId(type.typeParameters), <GenericType>type);
type.target = <GenericType>type;
type.typeArguments = type.typeParameters;
type.thisType = <TypeParameter>createType(TypeFlags.TypeParameter);
type.thisType = createTypeParameter();
type.thisType.isThisType = true;
type.thisType.constraint = type;
type.declaredProperties = properties;
@@ -9971,7 +9967,7 @@ namespace ts {
if (checkType === wildcardType || extendsType === wildcardType) {
return wildcardType;
}
const checkTypeInstantiable = maybeTypeOfKind(checkType, TypeFlags.Instantiable);
const checkTypeInstantiable = maybeTypeOfKind(checkType, TypeFlags.Instantiable | TypeFlags.GenericMappedType);
let combinedMapper: TypeMapper | undefined;
if (root.inferTypeParameters) {
const context = createInferenceContext(root.inferTypeParameters, /*signature*/ undefined, InferenceFlags.None);
@@ -9986,7 +9982,7 @@ namespace ts {
// Instantiate the extends type including inferences for 'infer T' type parameters
const inferredExtendsType = combinedMapper ? instantiateType(root.extendsType, combinedMapper) : extendsType;
// We attempt to resolve the conditional type only when the check and extends types are non-generic
if (!checkTypeInstantiable && !maybeTypeOfKind(inferredExtendsType, TypeFlags.Instantiable)) {
if (!checkTypeInstantiable && !maybeTypeOfKind(inferredExtendsType, TypeFlags.Instantiable | TypeFlags.GenericMappedType)) {
if (inferredExtendsType.flags & TypeFlags.AnyOrUnknown) {
return instantiateType(root.trueType, mapper);
}
@@ -9998,14 +9994,15 @@ namespace ts {
// types with type parameters mapped to the wildcard type, the most permissive instantiations
// possible (the wildcard type is assignable to and from all types). If those are not related,
// then no instatiations will be and we can just return the false branch type.
if (!isTypeAssignableTo(getWildcardInstantiation(checkType), getWildcardInstantiation(inferredExtendsType))) {
if (!isTypeAssignableTo(getPermissiveInstantiation(checkType), getPermissiveInstantiation(inferredExtendsType))) {
return instantiateType(root.falseType, mapper);
}
// Return trueType for a definitely true extends check. The definitely assignable relation excludes
// type variable constraints from consideration. Without the definitely assignable relation, the type
// Return trueType for a definitely true extends check. We check instantiations of the two
// types with type parameters mapped to their restrictive form, i.e. a form of the type parameter
// that has no constraint. This ensures that, for example, the type
// type Foo<T extends { x: any }> = T extends { x: string } ? string : number
// would immediately resolve to 'string' instead of being deferred.
if (checkTypeRelatedTo(checkType, inferredExtendsType, definitelyAssignableRelation, /*errorNode*/ undefined)) {
// doesn't immediately resolve to 'string' instead of being deferred.
if (isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(inferredExtendsType))) {
return instantiateType(root.trueType, combinedMapper || mapper);
}
}
@@ -10611,13 +10608,20 @@ namespace ts {
return t => t === source ? target : baseMapper(t);
}
function wildcardMapper(type: Type) {
function permissiveMapper(type: Type) {
return type.flags & TypeFlags.TypeParameter ? wildcardType : type;
}
function getRestrictiveTypeParameter(tp: TypeParameter) {
return !tp.constraint ? tp : tp.restrictiveInstantiation || (tp.restrictiveInstantiation = createTypeParameter(tp.symbol));
}
function restrictiveMapper(type: Type) {
return type.flags & TypeFlags.TypeParameter ? getRestrictiveTypeParameter(<TypeParameter>type) : type;
}
function cloneTypeParameter(typeParameter: TypeParameter): TypeParameter {
const result = <TypeParameter>createType(TypeFlags.TypeParameter);
result.symbol = typeParameter.symbol;
const result = createTypeParameter(typeParameter.symbol);
result.target = typeParameter;
return result;
}
@@ -10969,9 +10973,14 @@ namespace ts {
return type;
}
function getWildcardInstantiation(type: Type) {
function getPermissiveInstantiation(type: Type) {
return type.flags & (TypeFlags.Primitive | TypeFlags.AnyOrUnknown | TypeFlags.Never) ? type :
type.wildcardInstantiation || (type.wildcardInstantiation = instantiateType(type, wildcardMapper));
type.permissiveInstantiation || (type.permissiveInstantiation = instantiateType(type, permissiveMapper));
}
function getRestrictiveInstantiation(type: Type) {
return type.flags & (TypeFlags.Primitive | TypeFlags.AnyOrUnknown | TypeFlags.Never) ? type :
type.restrictiveInstantiation || (type.restrictiveInstantiation = instantiateType(type, restrictiveMapper));
}
function instantiateIndexInfo(info: IndexInfo | undefined, mapper: TypeMapper): IndexInfo | undefined {
@@ -11644,7 +11653,7 @@ namespace ts {
if (s & TypeFlags.Null && (!strictNullChecks || t & TypeFlags.Null)) return true;
if (s & TypeFlags.Object && t & TypeFlags.NonPrimitive) return true;
if (s & TypeFlags.UniqueESSymbol || t & TypeFlags.UniqueESSymbol) return false;
if (relation === assignableRelation || relation === definitelyAssignableRelation || relation === comparableRelation) {
if (relation === assignableRelation || relation === comparableRelation) {
if (s & TypeFlags.Any) return true;
// Type number or any numeric literal type is assignable to any numeric enum type or any
// numeric enum literal type. This rule exists for backwards compatibility reasons because
@@ -11836,7 +11845,7 @@ namespace ts {
target = (<FreshableType>target).regularType;
}
if (source.flags & TypeFlags.Substitution) {
source = relation === definitelyAssignableRelation ? (<SubstitutionType>source).typeVariable : (<SubstitutionType>source).substitute;
source = (<SubstitutionType>source).substitute;
}
if (target.flags & TypeFlags.Substitution) {
target = (<SubstitutionType>target).typeVariable;
@@ -12022,7 +12031,7 @@ namespace ts {
}
if (isExcessPropertyCheckTarget(target)) {
const isComparingJsxAttributes = !!(getObjectFlags(source) & ObjectFlags.JsxAttributes);
if ((relation === assignableRelation || relation === definitelyAssignableRelation || relation === comparableRelation) &&
if ((relation === assignableRelation || relation === comparableRelation) &&
(isTypeSubsetOf(globalObjectType, target) || (!isComparingJsxAttributes && isEmptyObjectType(target)))) {
return false;
}
@@ -12425,24 +12434,22 @@ namespace ts {
}
// A type S is assignable to keyof T if S is assignable to keyof C, where C is the
// simplified form of T or, if T doesn't simplify, the constraint of T.
if (relation !== definitelyAssignableRelation) {
const simplified = getSimplifiedType((<IndexType>target).type);
const constraint = simplified !== (<IndexType>target).type ? simplified : getConstraintOfType((<IndexType>target).type);
if (constraint) {
// We require Ternary.True here such that circular constraints don't cause
// false positives. For example, given 'T extends { [K in keyof T]: string }',
// 'keyof T' has itself as its constraint and produces a Ternary.Maybe when
// related to other types.
if (isRelatedTo(source, getIndexType(constraint, (target as IndexType).stringsOnly), reportErrors) === Ternary.True) {
return Ternary.True;
}
const simplified = getSimplifiedType((<IndexType>target).type);
const constraint = simplified !== (<IndexType>target).type ? simplified : getConstraintOfType((<IndexType>target).type);
if (constraint) {
// We require Ternary.True here such that circular constraints don't cause
// false positives. For example, given 'T extends { [K in keyof T]: string }',
// 'keyof T' has itself as its constraint and produces a Ternary.Maybe when
// related to other types.
if (isRelatedTo(source, getIndexType(constraint, (target as IndexType).stringsOnly), reportErrors) === Ternary.True) {
return Ternary.True;
}
}
}
else if (target.flags & TypeFlags.IndexedAccess) {
// A type S is related to a type T[K], where T and K aren't both type variables, if S is related to C,
// where C is the base constraint of T[K]
if (relation !== identityRelation && relation !== definitelyAssignableRelation &&
if (relation !== identityRelation &&
!(isGenericObjectType((<IndexedAccessType>target).objectType) && isGenericIndexType((<IndexedAccessType>target).indexType))) {
const constraint = getBaseConstraintOfType(target);
if (constraint && constraint !== target) {
@@ -12485,26 +12492,24 @@ namespace ts {
return result;
}
}
if (relation !== definitelyAssignableRelation) {
const constraint = getConstraintOfType(<TypeParameter>source);
if (!constraint || (source.flags & TypeFlags.TypeParameter && constraint.flags & TypeFlags.Any)) {
// A type variable with no constraint is not related to the non-primitive object type.
if (result = isRelatedTo(emptyObjectType, extractTypesOfKind(target, ~TypeFlags.NonPrimitive))) {
errorInfo = saveErrorInfo;
return result;
}
}
// hi-speed no-this-instantiation check (less accurate, but avoids costly `this`-instantiation when the constraint will suffice), see #28231 for report on why this is needed
else if (result = isRelatedTo(constraint, target, /*reportErrors*/ false, /*headMessage*/ undefined, isIntersectionConstituent)) {
errorInfo = saveErrorInfo;
return result;
}
// slower, fuller, this-instantiated check (necessary when comparing raw `this` types from base classes), see `subclassWithPolymorphicThisIsAssignable.ts` test for example
else if (result = isRelatedTo(getTypeWithThisArgument(constraint, source), target, reportErrors, /*headMessage*/ undefined, isIntersectionConstituent)) {
const constraint = getConstraintOfType(<TypeParameter>source);
if (!constraint || (source.flags & TypeFlags.TypeParameter && constraint.flags & TypeFlags.Any)) {
// A type variable with no constraint is not related to the non-primitive object type.
if (result = isRelatedTo(emptyObjectType, extractTypesOfKind(target, ~TypeFlags.NonPrimitive))) {
errorInfo = saveErrorInfo;
return result;
}
}
// hi-speed no-this-instantiation check (less accurate, but avoids costly `this`-instantiation when the constraint will suffice), see #28231 for report on why this is needed
else if (result = isRelatedTo(constraint, target, /*reportErrors*/ false, /*headMessage*/ undefined, isIntersectionConstituent)) {
errorInfo = saveErrorInfo;
return result;
}
// slower, fuller, this-instantiated check (necessary when comparing raw `this` types from base classes), see `subclassWithPolymorphicThisIsAssignable.ts` test for example
else if (result = isRelatedTo(getTypeWithThisArgument(constraint, source), target, reportErrors, /*headMessage*/ undefined, isIntersectionConstituent)) {
errorInfo = saveErrorInfo;
return result;
}
}
else if (source.flags & TypeFlags.Index) {
if (result = isRelatedTo(keyofConstraintType, target, reportErrors)) {
@@ -12528,7 +12533,7 @@ namespace ts {
}
}
}
else if (relation !== definitelyAssignableRelation) {
else {
const distributiveConstraint = getConstraintOfDistributiveConditionalType(<ConditionalType>source);
if (distributiveConstraint) {
if (result = isRelatedTo(distributiveConstraint, target, reportErrors)) {
@@ -12559,9 +12564,6 @@ namespace ts {
}
return Ternary.False;
}
if (relation === definitelyAssignableRelation && isGenericMappedType(source)) {
return Ternary.False;
}
const sourceIsPrimitive = !!(source.flags & TypeFlags.Primitive);
if (relation !== identityRelation) {
source = getApparentType(source);

4
src/compiler/types.ts
View File

@@ -3916,7 +3916,9 @@ namespace ts {
aliasTypeArguments?: ReadonlyArray<Type>; // Alias type arguments (if any)
/* @internal */ aliasTypeArgumentsContainsMarker?: boolean; // Alias type arguments (if any)
/* @internal */
wildcardInstantiation?: Type; // Instantiation with type parameters mapped to wildcard type
permissiveInstantiation?: Type; // Instantiation with type parameters mapped to wildcard type
/* @internal */
restrictiveInstantiation?: Type; // Instantiation with type parameters mapped to unconstrained form
/* @internal */
immediateBaseConstraint?: Type; // Immediate base constraint cache
}