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Merge pull request #15104 from Microsoft/covariantCallbacks

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Covariant checking for callback parameters
This commit is contained in:
Anders Hejlsberg
2017-04-18 11:35:21 -07:00
committed by GitHub
parent 60fe5a87f6 3cda0eac32
commit cef42c97fe
21 changed files with 727 additions and 154 deletions
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32
src/compiler/checker.ts
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@@ -8206,7 +8206,8 @@ namespace ts {
function isSignatureAssignableTo(source: Signature,
target: Signature,
ignoreReturnTypes: boolean): boolean {
return compareSignaturesRelated(source, target, ignoreReturnTypes, /*reportErrors*/ false, /*errorReporter*/ undefined, compareTypesAssignable) !== Ternary.False;
return compareSignaturesRelated(source, target, /*checkAsCallback*/ false, ignoreReturnTypes, /*reportErrors*/ false,
/*errorReporter*/ undefined, compareTypesAssignable) !== Ternary.False;
}
type ErrorReporter = (message: DiagnosticMessage, arg0?: string, arg1?: string) => void;
@@ -8216,6 +8217,7 @@ namespace ts {
*/
function compareSignaturesRelated(source: Signature,
target: Signature,
checkAsCallback: boolean,
ignoreReturnTypes: boolean,
reportErrors: boolean,
errorReporter: ErrorReporter,
@@ -8258,9 +8260,23 @@ namespace ts {
const sourceParams = source.parameters;
const targetParams = target.parameters;
for (let i = 0; i < checkCount; i++) {
const s = i < sourceMax ? getTypeOfParameter(sourceParams[i]) : getRestTypeOfSignature(source);
const t = i < targetMax ? getTypeOfParameter(targetParams[i]) : getRestTypeOfSignature(target);
const related = compareTypes(s, t, /*reportErrors*/ false) || compareTypes(t, s, reportErrors);
const sourceType = i < sourceMax ? getTypeOfParameter(sourceParams[i]) : getRestTypeOfSignature(source);
const targetType = i < targetMax ? getTypeOfParameter(targetParams[i]) : getRestTypeOfSignature(target);
const sourceSig = getSingleCallSignature(getNonNullableType(sourceType));
const targetSig = getSingleCallSignature(getNonNullableType(targetType));
// In order to ensure that any generic type Foo<T> is at least co-variant with respect to T no matter
// how Foo uses T, we need to relate parameters bi-variantly (given that parameters are input positions,
// they naturally relate only contra-variantly). However, if the source and target parameters both have
// function types with a single call signature, we known we are relating two callback parameters. In
// that case it is sufficient to only relate the parameters of the signatures co-variantly because,
// similar to return values, callback parameters are output positions. This means that a Promise<T>,
// where T is used only in callback parameter positions, will be co-variant (as opposed to bi-variant)
// with respect to T.
const callbacks = sourceSig && targetSig && !sourceSig.typePredicate && !targetSig.typePredicate &&
(getFalsyFlags(sourceType) & TypeFlags.Nullable) === (getFalsyFlags(targetType) & TypeFlags.Nullable);
const related = callbacks ?
compareSignaturesRelated(targetSig, sourceSig, /*checkAsCallback*/ true, /*ignoreReturnTypes*/ false, reportErrors, errorReporter, compareTypes) :
!checkAsCallback && compareTypes(sourceType, targetType, /*reportErrors*/ false) || compareTypes(targetType, sourceType, reportErrors);
if (!related) {
if (reportErrors) {
errorReporter(Diagnostics.Types_of_parameters_0_and_1_are_incompatible,
@@ -8292,7 +8308,11 @@ namespace ts {
}
}
else {
result &= compareTypes(sourceReturnType, targetReturnType, reportErrors);
// When relating callback signatures, we still need to relate return types bi-variantly as otherwise
// the containing type wouldn't be co-variant. For example, interface Foo<T> { add(cb: () => T): void }
// wouldn't be co-variant for T without this rule.
result &= checkAsCallback && compareTypes(targetReturnType, sourceReturnType, /*reportErrors*/ false) ||
compareTypes(sourceReturnType, targetReturnType, reportErrors);
}
}
@@ -9260,7 +9280,7 @@ namespace ts {
* See signatureAssignableTo, compareSignaturesIdentical
*/
function signatureRelatedTo(source: Signature, target: Signature, reportErrors: boolean): Ternary {
return compareSignaturesRelated(source, target, /*ignoreReturnTypes*/ false, reportErrors, reportError, isRelatedTo);
return compareSignaturesRelated(source, target, /*checkAsCallback*/ false, /*ignoreReturnTypes*/ false, reportErrors, reportError, isRelatedTo);
}
function signaturesIdenticalTo(source: Type, target: Type, kind: SignatureKind): Ternary {

2
src/compiler/parser.ts
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@@ -57,7 +57,7 @@ namespace ts {
// The visitXXX functions could be written as local functions that close over the cbNode and cbNodeArray
// callback parameters, but that causes a closure allocation for each invocation with noticeable effects
// on performance.
const visitNodes: (cb: (node: Node | Node[]) => T, nodes: Node[]) => T = cbNodeArray ? visitNodeArray : visitEachNode;
const visitNodes: (cb: ((node: Node) => T) | ((node: Node[]) => T), nodes: Node[]) => T = cbNodeArray ? visitNodeArray : visitEachNode;
const cbNodes = cbNodeArray || cbNode;
switch (node.kind) {
case SyntaxKind.QualifiedName:

2
src/compiler/visitor.ts
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@@ -885,7 +885,7 @@ namespace ts {
return initial;
}
const reduceNodes: (nodes: NodeArray<Node>, f: (memo: T, node: Node | NodeArray<Node>) => T, initial: T) => T = cbNodeArray ? reduceNodeArray : reduceLeft;
const reduceNodes: (nodes: NodeArray<Node>, f: ((memo: T, node: Node) => T) | ((memo: T, node: NodeArray<Node>) => T), initial: T) => T = cbNodeArray ? reduceNodeArray : reduceLeft;
const cbNodes = cbNodeArray || cbNode;
const kind = node.kind;