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Improve detection and handling of circular generic constraints

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This commit is contained in:
Anders Hejlsberg
2017-01-06 16:47:33 -08:00
parent 88c68256e6
commit 06aa905d20
1 changed files with 100 additions and 74 deletions
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174
src/compiler/checker.ts
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@@ -164,6 +164,7 @@ namespace ts {
anyFunctionType.flags |= TypeFlags.ContainsAnyFunctionType;
const noConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
const circularConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
const anySignature = createSignature(undefined, undefined, undefined, emptyArray, anyType, /*typePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
const unknownSignature = createSignature(undefined, undefined, undefined, emptyArray, unknownType, /*typePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
@@ -4135,9 +4136,6 @@ namespace ts {
if (!links.declaredType) {
const type = <TypeParameter>createType(TypeFlags.TypeParameter);
type.symbol = symbol;
if (!(<TypeParameterDeclaration>getDeclarationOfKind(symbol, SyntaxKind.TypeParameter)).constraint) {
type.constraint = noConstraintType;
}
links.declaredType = type;
}
return <TypeParameter>links.declaredType;
@@ -4754,19 +4752,79 @@ namespace ts {
getPropertiesOfObjectType(type);
}
function getConstraintOfTypeVariable(type: TypeVariable): Type {
return type.flags & TypeFlags.TypeParameter ? getConstraintOfTypeParameter(<TypeParameter>type) : getBaseConstraintOfTypeVariable(type);
}
function getConstraintOfTypeParameter(typeParameter: TypeParameter): Type {
return hasNonCircularBaseConstraint(typeParameter) ? getConstraintFromTypeParameter(typeParameter) : undefined;
}
function getBaseConstraintOfTypeVariable(type: TypeVariable): Type {
const constraint = getResolvedBaseConstraint(type);
return constraint !== noConstraintType && constraint !== circularConstraintType ? constraint : undefined;
}
function hasNonCircularBaseConstraint(type: TypeVariable): boolean {
return getResolvedBaseConstraint(type) !== circularConstraintType;
}
/**
* The apparent type of a type parameter is the base constraint instantiated with the type parameter
* as the type argument for the 'this' type.
* Return the resolved base constraint of a type variable. The noConstraintType singleton is returned if the
* type variable has no constraint, and the circularConstraintType singleton is returned if the constraint
* circularly references the type variable.
*/
function getApparentTypeOfTypeVariable(type: TypeVariable) {
function getResolvedBaseConstraint(type: TypeVariable): Type {
let typeStack: Type[];
let circular: boolean;
if (!type.resolvedApparentType) {
let constraintType = getConstraintOfTypeVariable(type);
while (constraintType && constraintType.flags & TypeFlags.TypeParameter) {
constraintType = getConstraintOfTypeVariable(<TypeVariable>constraintType);
}
type.resolvedApparentType = getTypeWithThisArgument(constraintType || emptyObjectType, type);
typeStack = [];
const constraint = getBaseConstraint(type);
type.resolvedApparentType = circular ? circularConstraintType : getTypeWithThisArgument(constraint || noConstraintType, type);
}
return type.resolvedApparentType;
function getBaseConstraint(t: Type): Type {
if (contains(typeStack, t)) {
circular = true;
return undefined;
}
typeStack.push(t);
const result = computeBaseConstraint(t);
typeStack.pop();
return result;
}
function computeBaseConstraint(t: Type): Type {
if (t.flags & TypeFlags.TypeParameter) {
const constraint = getConstraintFromTypeParameter(<TypeParameter>t);
return (<TypeParameter>t).isThisType ? constraint :
constraint ? getBaseConstraint(constraint) : undefined;
}
if (t.flags & TypeFlags.UnionOrIntersection) {
const types = (<UnionOrIntersectionType>t).types;
const baseTypes: Type[] = [];
for (const type of types) {
const baseType = getBaseConstraint(type);
if (baseType) {
baseTypes.push(baseType);
}
}
return t.flags & TypeFlags.Union && baseTypes.length === types.length ? getUnionType(baseTypes) :
t.flags & TypeFlags.Intersection && baseTypes.length ? getIntersectionType(baseTypes) :
undefined;
}
if (t.flags & TypeFlags.Index) {
return stringType;
}
if (t.flags & TypeFlags.IndexedAccess) {
const baseObjectType = getBaseConstraint((<IndexedAccessType>t).objectType);
const baseIndexType = getBaseConstraint((<IndexedAccessType>t).indexType);
const baseIndexedAccess = baseObjectType && baseIndexType ? getIndexedAccessType(baseObjectType, baseIndexType) : undefined;
return baseIndexedAccess && baseIndexedAccess !== unknownType ? getBaseConstraint(baseIndexedAccess) : undefined;
}
return t;
}
}
/**
@@ -4775,7 +4833,7 @@ namespace ts {
* type itself. Note that the apparent type of a union type is the union type itself.
*/
function getApparentType(type: Type): Type {
const t = type.flags & TypeFlags.TypeVariable ? getApparentTypeOfTypeVariable(<TypeVariable>type) : type;
const t = type.flags & TypeFlags.TypeVariable ? getBaseConstraintOfTypeVariable(<TypeVariable>type) || emptyObjectType : type;
return t.flags & TypeFlags.StringLike ? globalStringType :
t.flags & TypeFlags.NumberLike ? globalNumberType :
t.flags & TypeFlags.BooleanLike ? globalBooleanType :
@@ -5329,20 +5387,7 @@ namespace ts {
return (<TypeParameterDeclaration>getDeclarationOfKind(type.symbol, SyntaxKind.TypeParameter)).constraint;
}
function hasConstraintReferenceTo(type: Type, target: TypeParameter): boolean {
let checked: Type[];
while (type && type.flags & TypeFlags.TypeParameter && !((type as TypeParameter).isThisType) && !contains(checked, type)) {
if (type === target) {
return true;
}
(checked || (checked = [])).push(type);
const constraintDeclaration = getConstraintDeclaration(<TypeParameter>type);
type = constraintDeclaration && getTypeFromTypeNode(constraintDeclaration);
}
return false;
}
function getConstraintOfTypeParameter(typeParameter: TypeParameter): Type {
function getConstraintFromTypeParameter(typeParameter: TypeParameter): Type {
if (!typeParameter.constraint) {
if (typeParameter.target) {
const targetConstraint = getConstraintOfTypeParameter(typeParameter.target);
@@ -5350,23 +5395,12 @@ namespace ts {
}
else {
const constraintDeclaration = getConstraintDeclaration(typeParameter);
let constraint = getTypeFromTypeNode(constraintDeclaration);
if (hasConstraintReferenceTo(constraint, typeParameter)) {
error(constraintDeclaration, Diagnostics.Type_parameter_0_has_a_circular_constraint, typeToString(typeParameter));
constraint = unknownType;
}
typeParameter.constraint = constraint;
typeParameter.constraint = constraintDeclaration ? getTypeFromTypeNode(constraintDeclaration) : noConstraintType;
}
}
return typeParameter.constraint === noConstraintType ? undefined : typeParameter.constraint;
}
function getConstraintOfTypeVariable(type: TypeVariable): Type {
return type.flags & TypeFlags.TypeParameter ? getConstraintOfTypeParameter(<TypeParameter>type) :
type.flags & TypeFlags.IndexedAccess ? (<IndexedAccessType>type).constraint :
undefined;
}
function getParentSymbolOfTypeParameter(typeParameter: TypeParameter): Symbol {
return getSymbolOfNode(getDeclarationOfKind(typeParameter.symbol, SyntaxKind.TypeParameter).parent);
}
@@ -6042,24 +6076,6 @@ namespace ts {
const type = <IndexedAccessType>createType(TypeFlags.IndexedAccess);
type.objectType = objectType;
type.indexType = indexType;
// We eagerly compute the constraint of the indexed access type such that circularity
// errors are immediately caught and reported. For example, class C { x: this["x"] }
// becomes an error only when the constraint is eagerly computed.
if (type.objectType.flags & TypeFlags.StructuredType) {
// The constraint of T[K], where T is an object, union, or intersection type,
// is the type of the string index signature of T, if any.
type.constraint = getIndexTypeOfType(type.objectType, IndexKind.String);
}
else if (type.objectType.flags & TypeFlags.TypeVariable) {
// The constraint of T[K], where T is a type variable, is A[K], where A is the
// apparent type of T.
const apparentType = getApparentTypeOfTypeVariable(<TypeVariable>type.objectType);
if (apparentType !== emptyObjectType) {
type.constraint = isTypeOfKind((<IndexedAccessType>type).indexType, TypeFlags.StringLike) ?
getIndexedAccessType(apparentType, (<IndexedAccessType>type).indexType) :
getIndexTypeOfType(apparentType, IndexKind.String);
}
}
return type;
}
@@ -6150,13 +6166,6 @@ namespace ts {
if (objectType.flags & TypeFlags.Any) {
return objectType;
}
// We first check that the index type is assignable to 'keyof T' for the object type.
if (accessNode) {
if (!isTypeAssignableTo(indexType, getIndexType(objectType))) {
error(accessNode, Diagnostics.Type_0_cannot_be_used_to_index_type_1, typeToString(indexType), typeToString(objectType));
return unknownType;
}
}
// If the object type is a mapped type { [P in K]: E }, we instantiate E using a mapper that substitutes
// the index type for P. For example, for an index access { [P in K]: Box<T[P]> }[X], we construct the
// type Box<T[X]>.
@@ -7436,8 +7445,9 @@ namespace ts {
}
// A type S is related to a type T[K] if S is related to A[K], where K is string-like and
// A is the apparent type of S.
if ((<IndexedAccessType>target).constraint) {
if (result = isRelatedTo(source, (<IndexedAccessType>target).constraint, reportErrors)) {
const constraint = getBaseConstraintOfTypeVariable(<IndexedAccessType>target);
if (constraint) {
if (result = isRelatedTo(source, constraint, reportErrors)) {
errorInfo = saveErrorInfo;
return result;
}
@@ -7475,8 +7485,9 @@ namespace ts {
else if (source.flags & TypeFlags.IndexedAccess) {
// A type S[K] is related to a type T if A[K] is related to T, where K is string-like and
// A is the apparent type of S.
if ((<IndexedAccessType>source).constraint) {
if (result = isRelatedTo((<IndexedAccessType>source).constraint, target, reportErrors)) {
const constraint = getBaseConstraintOfTypeVariable(<IndexedAccessType>source);
if (constraint) {
if (result = isRelatedTo(constraint, target, reportErrors)) {
errorInfo = saveErrorInfo;
return result;
}
@@ -12528,7 +12539,7 @@ namespace ts {
return unknownType;
}
return getIndexedAccessType(objectType, indexType, node);
return checkIndexedAccessIndexType(getIndexedAccessType(objectType, indexType, node), node);
}
function checkThatExpressionIsProperSymbolReference(expression: Expression, expressionType: Type, reportError: boolean): boolean {
@@ -15186,14 +15197,14 @@ namespace ts {
function isLiteralContextualType(contextualType: Type) {
if (contextualType) {
if (contextualType.flags & TypeFlags.TypeVariable) {
const apparentType = getApparentTypeOfTypeVariable(<TypeVariable>contextualType);
const constraint = getBaseConstraintOfTypeVariable(<TypeVariable>contextualType) || emptyObjectType;
// If the type parameter is constrained to the base primitive type we're checking for,
// consider this a literal context. For example, given a type parameter 'T extends string',
// this causes us to infer string literal types for T.
if (apparentType.flags & (TypeFlags.String | TypeFlags.Number | TypeFlags.Boolean | TypeFlags.Enum)) {
if (constraint.flags & (TypeFlags.String | TypeFlags.Number | TypeFlags.Boolean | TypeFlags.Enum)) {
return true;
}
contextualType = apparentType;
contextualType = constraint;
}
return maybeTypeOfKind(contextualType, (TypeFlags.Literal | TypeFlags.Index));
}
@@ -15391,6 +15402,10 @@ namespace ts {
}
checkSourceElement(node.constraint);
const typeParameter = getDeclaredTypeOfTypeParameter(getSymbolOfNode(node));
if (!hasNonCircularBaseConstraint(typeParameter)) {
error(node.constraint, Diagnostics.Type_parameter_0_has_a_circular_constraint, typeToString(typeParameter));
}
getConstraintOfTypeParameter(getDeclaredTypeOfTypeParameter(getSymbolOfNode(node)));
if (produceDiagnostics) {
checkTypeNameIsReserved(node.name, Diagnostics.Type_parameter_name_cannot_be_0);
@@ -16014,8 +16029,20 @@ namespace ts {
forEach(node.types, checkSourceElement);
}
function checkIndexedAccessIndexType(type: Type, accessNode: ElementAccessExpression | IndexedAccessTypeNode) {
if (type.flags & TypeFlags.IndexedAccess) {
// Check that the index type is assignable to 'keyof T' for the object type.
const objectType = (<IndexedAccessType>type).objectType;
const indexType = (<IndexedAccessType>type).indexType;
if (!isTypeAssignableTo(indexType, getIndexType(objectType))) {
error(accessNode, Diagnostics.Type_0_cannot_be_used_to_index_type_1, typeToString(indexType), typeToString(objectType));
}
}
return type;
}
function checkIndexedAccessType(node: IndexedAccessTypeNode) {
getTypeFromIndexedAccessTypeNode(node);
checkIndexedAccessIndexType(getTypeFromIndexedAccessTypeNode(node), node);
}
function checkMappedType(node: MappedTypeNode) {
@@ -16023,8 +16050,7 @@ namespace ts {
checkSourceElement(node.type);
const type = <MappedType>getTypeFromMappedTypeNode(node);
const constraintType = getConstraintTypeFromMappedType(type);
const keyType = constraintType.flags & TypeFlags.TypeVariable ? getApparentTypeOfTypeVariable(<TypeVariable>constraintType) : constraintType;
checkTypeAssignableTo(keyType, stringType, node.typeParameter.constraint);
checkTypeAssignableTo(constraintType, stringType, node.typeParameter.constraint);
}
function isPrivateWithinAmbient(node: Node): boolean {