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Limit type argument inference from binding patterns (#49086)

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* WIP

* Don’t widen literals based on bogus contextual type instantiation

* Split tests

* Skip unnecessary inference pass

* Accept test baselines

* Fix stray edit

* Fix type mapper combination

* Revert src/ of 7dc1952a82

* Make empty binding pattern provide no contextual type

* Add missed baseline
This commit is contained in:
Andrew Branch
2022-05-24 09:05:34 -07:00
committed by GitHub
parent 194a2aea0d
commit a2b785b6cb
29 changed files with 604 additions and 97 deletions
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72
src/compiler/checker.ts
View File

@@ -26519,7 +26519,7 @@ namespace ts {
if (result) {
return result;
}
if (!(contextFlags! & ContextFlags.SkipBindingPatterns) && isBindingPattern(declaration.name)) { // This is less a contextual type and more an implied shape - in some cases, this may be undesirable
if (!(contextFlags! & ContextFlags.SkipBindingPatterns) && isBindingPattern(declaration.name) && declaration.name.elements.length > 0) {
return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ true, /*reportErrors*/ false);
}
}
@@ -27053,22 +27053,20 @@ namespace ts {
const inferenceContext = getInferenceContext(node);
// If no inferences have been made, nothing is gained from instantiating as type parameters
// would just be replaced with their defaults similar to the apparent type.
if (inferenceContext && some(inferenceContext.inferences, hasInferenceCandidates)) {
if (inferenceContext && contextFlags! & ContextFlags.Signature && some(inferenceContext.inferences, hasInferenceCandidates)) {
// For contextual signatures we incorporate all inferences made so far, e.g. from return
// types as well as arguments to the left in a function call.
if (contextFlags && contextFlags & ContextFlags.Signature) {
return instantiateInstantiableTypes(contextualType, inferenceContext.nonFixingMapper);
}
return instantiateInstantiableTypes(contextualType, inferenceContext.nonFixingMapper);
}
if (inferenceContext?.returnMapper) {
// For other purposes (e.g. determining whether to produce literal types) we only
// incorporate inferences made from the return type in a function call. We remove
// the 'boolean' type from the contextual type such that contextually typed boolean
// literals actually end up widening to 'boolean' (see #48363).
if (inferenceContext.returnMapper) {
const type = instantiateInstantiableTypes(contextualType, inferenceContext.returnMapper);
return type.flags & TypeFlags.Union && containsType((type as UnionType).types, regularFalseType) && containsType((type as UnionType).types, regularTrueType) ?
filterType(type, t => t !== regularFalseType && t !== regularTrueType) :
type;
}
const type = instantiateInstantiableTypes(contextualType, inferenceContext.returnMapper);
return type.flags & TypeFlags.Union && containsType((type as UnionType).types, regularFalseType) && containsType((type as UnionType).types, regularTrueType) ?
filterType(type, t => t !== regularFalseType && t !== regularTrueType) :
type;
}
}
return contextualType;
@@ -29904,29 +29902,43 @@ namespace ts {
// 'let f: (x: string) => number = wrap(s => s.length)', we infer from the declared type of 'f' to the
// return type of 'wrap'.
if (node.kind !== SyntaxKind.Decorator) {
const contextualType = getContextualType(node, every(signature.typeParameters, p => !!getDefaultFromTypeParameter(p)) ? ContextFlags.SkipBindingPatterns : ContextFlags.None);
const skipBindingPatterns = every(signature.typeParameters, p => !!getDefaultFromTypeParameter(p));
const contextualType = getContextualType(node, skipBindingPatterns ? ContextFlags.SkipBindingPatterns : ContextFlags.None);
if (contextualType) {
const inferenceTargetType = getReturnTypeOfSignature(signature);
if (couldContainTypeVariables(inferenceTargetType)) {
// We clone the inference context to avoid disturbing a resolution in progress for an
// outer call expression. Effectively we just want a snapshot of whatever has been
// inferred for any outer call expression so far.
const outerContext = getInferenceContext(node);
const outerMapper = getMapperFromContext(cloneInferenceContext(outerContext, InferenceFlags.NoDefault));
const instantiatedType = instantiateType(contextualType, outerMapper);
// If the contextual type is a generic function type with a single call signature, we
// instantiate the type with its own type parameters and type arguments. This ensures that
// the type parameters are not erased to type any during type inference such that they can
// be inferred as actual types from the contextual type. For example:
// declare function arrayMap<T, U>(f: (x: T) => U): (a: T[]) => U[];
// const boxElements: <A>(a: A[]) => { value: A }[] = arrayMap(value => ({ value }));
// Above, the type of the 'value' parameter is inferred to be 'A'.
const contextualSignature = getSingleCallSignature(instantiatedType);
const inferenceSourceType = contextualSignature && contextualSignature.typeParameters ?
getOrCreateTypeFromSignature(getSignatureInstantiationWithoutFillingInTypeArguments(contextualSignature, contextualSignature.typeParameters)) :
instantiatedType;
// Inferences made from return types have lower priority than all other inferences.
inferTypes(context.inferences, inferenceSourceType, inferenceTargetType, InferencePriority.ReturnType);
const isFromBindingPattern = !skipBindingPatterns && getContextualType(node, ContextFlags.SkipBindingPatterns) !== contextualType;
// A return type inference from a binding pattern can be used in instantiating the contextual
// type of an argument later in inference, but cannot stand on its own as the final return type.
// It is incorporated into `context.returnMapper` which is used in `instantiateContextualType`,
// but doesn't need to go into `context.inferences`. This allows a an array binding pattern to
// produce a tuple for `T` in
// declare function f<T>(cb: () => T): T;
// const [e1, e2, e3] = f(() => [1, "hi", true]);
// but does not produce any inference for `T` in
// declare function f<T>(): T;
// const [e1, e2, e3] = f();
if (!isFromBindingPattern) {
// We clone the inference context to avoid disturbing a resolution in progress for an
// outer call expression. Effectively we just want a snapshot of whatever has been
// inferred for any outer call expression so far.
const outerMapper = getMapperFromContext(cloneInferenceContext(outerContext, InferenceFlags.NoDefault));
const instantiatedType = instantiateType(contextualType, outerMapper);
// If the contextual type is a generic function type with a single call signature, we
// instantiate the type with its own type parameters and type arguments. This ensures that
// the type parameters are not erased to type any during type inference such that they can
// be inferred as actual types from the contextual type. For example:
// declare function arrayMap<T, U>(f: (x: T) => U): (a: T[]) => U[];
// const boxElements: <A>(a: A[]) => { value: A }[] = arrayMap(value => ({ value }));
// Above, the type of the 'value' parameter is inferred to be 'A'.
const contextualSignature = getSingleCallSignature(instantiatedType);
const inferenceSourceType = contextualSignature && contextualSignature.typeParameters ?
getOrCreateTypeFromSignature(getSignatureInstantiationWithoutFillingInTypeArguments(contextualSignature, contextualSignature.typeParameters)) :
instantiatedType;
// Inferences made from return types have lower priority than all other inferences.
inferTypes(context.inferences, inferenceSourceType, inferenceTargetType, InferencePriority.ReturnType);
}
// Create a type mapper for instantiating generic contextual types using the inferences made
// from the return type. We need a separate inference pass here because (a) instantiation of
// the source type uses the outer context's return mapper (which excludes inferences made from

2
src/compiler/types.ts
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@@ -5874,7 +5874,7 @@ namespace ts {
ReturnType = 1 << 7, // Inference made from return type of generic function
LiteralKeyof = 1 << 8, // Inference made from a string literal to a keyof T
NoConstraints = 1 << 9, // Don't infer from constraints of instantiable types
AlwaysStrict = 1 << 10, // Always use strict rules for contravariant inferences
AlwaysStrict = 1 << 10, // Always use strict rules for contravariant inferences
MaxValue = 1 << 11, // Seed for inference priority tracking
PriorityImpliesCombination = ReturnType | MappedTypeConstraint | LiteralKeyof, // These priorities imply that the resulting type should be a combination of all candidates