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Infer non-narrowing predicates when the contextual signature is a type predicate #60834

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Infer non-narrowing predicates when the contextual signature is a type predicate #60834

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Infer non-narrowing predicates when the contextual signature is a typ…
Andarist Dec 20, 2024
e10853f
handle boolean literals
Andarist Dec 21, 2024
1a36871
update baselines
Andarist Dec 21, 2024
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55 changes: 29 additions & 26 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -38778,7 +38778,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}
}

function getTypePredicateFromBody(func: FunctionLikeDeclaration): TypePredicate | undefined {
function getTypePredicateFromBody(func: FunctionLikeDeclaration, contextualTypePredicate?: IdentifierTypePredicate): TypePredicate | undefined {
switch (func.kind) {
case SyntaxKind.Constructor:
case SyntaxKind.GetAccessor:
Expand All @@ -38800,41 +38800,43 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
});
if (bailedEarly || !singleReturn || functionHasImplicitReturn(func)) return undefined;
}
return checkIfExpressionRefinesAnyParameter(func, singleReturn);
}

function checkIfExpressionRefinesAnyParameter(func: FunctionLikeDeclaration, expr: Expression): TypePredicate | undefined {
expr = skipParentheses(expr, /*excludeJSDocTypeAssertions*/ true);
const expr = skipParentheses(singleReturn, /*excludeJSDocTypeAssertions*/ true);
const returnType = checkExpressionCached(expr);
if (!(returnType.flags & TypeFlags.Boolean)) return undefined;

return forEach(func.parameters, (param, i) => {
const initType = getTypeOfSymbol(param.symbol);
if (!initType || initType.flags & TypeFlags.Boolean || !isIdentifier(param.name) || isSymbolAssigned(param.symbol) || isRestParameter(param)) {
// Refining "x: boolean" to "x is true" or "x is false" isn't useful.
return;
}
const trueType = checkIfExpressionRefinesParameter(func, expr, param, initType);
if (trueType) {
return createTypePredicate(TypePredicateKind.Identifier, unescapeLeadingUnderscores(param.name.escapedText), i, trueType);
if (contextualTypePredicate && returnType.flags & TypeFlags.BooleanLiteral) {
const param = func.parameters[contextualTypePredicate.parameterIndex];
if (!isIdentifier(param.name)) {
return undefined;
}
});
const refinedType = (returnType as IntrinsicType).intrinsicName === "true" ? getTypeOfSymbol(param.symbol) : neverType;
return createTypePredicate(TypePredicateKind.Identifier, unescapeLeadingUnderscores(param.name.escapedText), contextualTypePredicate.parameterIndex, refinedType);
}
if (!(returnType.flags & TypeFlags.Boolean)) return undefined;
return contextualTypePredicate ?
getTypePredicateIfRefinesParameterAtIndex(func, expr, contextualTypePredicate, contextualTypePredicate.parameterIndex) :
forEach(func.parameters, (_, i) => getTypePredicateIfRefinesParameterAtIndex(func, expr, contextualTypePredicate, i));
}

function checkIfExpressionRefinesParameter(func: FunctionLikeDeclaration, expr: Expression, param: ParameterDeclaration, initType: Type): Type | undefined {
function getTypePredicateIfRefinesParameterAtIndex(func: FunctionLikeDeclaration, expr: Expression, contextualTypePredicate: IdentifierTypePredicate | undefined, parameterIndex: number): TypePredicate | undefined {
const param = func.parameters[parameterIndex];
const initType = getTypeOfSymbol(param.symbol);
if (!initType || initType.flags & TypeFlags.Boolean || !isIdentifier(param.name) || isSymbolAssigned(param.symbol) || isRestParameter(param)) {
// Refining "x: boolean" to "x is true" or "x is false" isn't useful.
return;
}
const antecedent = canHaveFlowNode(expr) && expr.flowNode ||
expr.parent.kind === SyntaxKind.ReturnStatement && (expr.parent as ReturnStatement).flowNode ||
createFlowNode(FlowFlags.Start, /*node*/ undefined, /*antecedent*/ undefined);
const trueCondition = createFlowNode(FlowFlags.TrueCondition, expr, antecedent);

const trueType = getFlowTypeOfReference(param.name, initType, initType, func, trueCondition);
if (trueType === initType) return undefined;

if (!contextualTypePredicate && trueType === initType) {
return undefined;
}
// "x is T" means that x is T if and only if it returns true. If it returns false then x is not T.
// This means that if the function is called with an argument of type trueType, there can't be anything left in the `else` branch. It must reduce to `never`.
const falseCondition = createFlowNode(FlowFlags.FalseCondition, expr, antecedent);
const falseSubtype = getFlowTypeOfReference(param.name, initType, trueType, func, falseCondition);
return falseSubtype.flags & TypeFlags.Never ? trueType : undefined;
return falseSubtype.flags & TypeFlags.Never ? createTypePredicate(TypePredicateKind.Identifier, unescapeLeadingUnderscores(param.name.escapedText), parameterIndex, trueType) : undefined;
}

/**
Expand Down Expand Up @@ -38978,10 +38980,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
inferFromAnnotatedParameters(signature, contextualSignature, inferenceContext!);
}
}
if (contextualSignature && !getReturnTypeFromAnnotation(node) && !signature.resolvedReturnType) {
const returnType = getReturnTypeFromBody(node, checkMode);
if (!signature.resolvedReturnType) {
signature.resolvedReturnType = returnType;
if (contextualSignature && !getReturnTypeFromAnnotation(node)) {
const returnType = signature.resolvedReturnType ?? getReturnTypeFromBody(node, checkMode);
signature.resolvedReturnType ??= returnType;
if (signature.resolvedReturnType.flags && TypeFlags.Boolean && contextualSignature.resolvedTypePredicate && contextualSignature.resolvedTypePredicate !== noTypePredicate && contextualSignature.resolvedTypePredicate.kind === TypePredicateKind.Identifier) {
signature.resolvedTypePredicate ??= getTypePredicateFromBody(node, contextualSignature.resolvedTypePredicate) ?? noTypePredicate;
}
}
checkSignatureDeclaration(node);
Expand Down
45 changes: 45 additions & 0 deletions tests/baselines/reference/inferContextualTypePredicates1.errors.txt
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@@ -0,0 +1,45 @@
inferContextualTypePredicates1.ts(17,7): error TS2322: Type '(a: string | null, b: string | null) => boolean' is not assignable to type '(a: string | null, b: string | null) => b is string'.
Signature '(a: string | null, b: string | null): boolean' must be a type predicate.


==== inferContextualTypePredicates1.ts (1 errors) ====
type Foo = { type: "foo"; foo: number };
type Bar = { type: "bar"; bar: string };

declare function skipIf<A, B extends A>(
as: A[],
predicate: (a: A) => a is B,
): Exclude<A, B>[];

declare const items: (Foo | Bar)[];

const r1 = skipIf(items, (item) => item.type === "foo"); // ok
const r2 = skipIf(items, (item) => item.type === "foo" || item.type === "bar"); // ok
const r3 = skipIf(items, (item) => false); // ok
const r4 = skipIf(items, (item) => true); // ok

const pred1: (a: string | null, b: string | null) => b is string = (a, b) => typeof b === 'string'; // ok
const pred2: (a: string | null, b: string | null) => b is string = (a, b) => typeof a === 'string'; // error
~~~~~
!!! error TS2322: Type '(a: string | null, b: string | null) => boolean' is not assignable to type '(a: string | null, b: string | null) => b is string'.
!!! error TS2322: Signature '(a: string | null, b: string | null): boolean' must be a type predicate.

export declare function every<T, U extends T>(array: readonly T[], callback: (element: T, index: number) => element is U): array is readonly U[];
export declare function every<T, U extends T>(array: readonly T[] | undefined, callback: (element: T, index: number) => element is U): array is readonly U[] | undefined;
export declare function every<T>(array: readonly T[] | undefined, callback: (element: T, index: number) => boolean): boolean;

type Type = {
kind: number;
flags: number;
};

function testEvery(typeSet: Type[]) {
if (every(typeSet, (t) => t.kind === 1)) {
return 1;
}
if (every(typeSet, (t) => t.kind === 2)) {
return 2;
}
return -1;
}

172 changes: 172 additions & 0 deletions tests/baselines/reference/inferContextualTypePredicates1.symbols
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Original file line number Diff line number Diff line change
@@ -0,0 +1,172 @@
//// [tests/cases/compiler/inferContextualTypePredicates1.ts] ////

=== inferContextualTypePredicates1.ts ===
type Foo = { type: "foo"; foo: number };
>Foo : Symbol(Foo, Decl(inferContextualTypePredicates1.ts, 0, 0))
>type : Symbol(type, Decl(inferContextualTypePredicates1.ts, 0, 12))
>foo : Symbol(foo, Decl(inferContextualTypePredicates1.ts, 0, 25))

type Bar = { type: "bar"; bar: string };
>Bar : Symbol(Bar, Decl(inferContextualTypePredicates1.ts, 0, 40))
>type : Symbol(type, Decl(inferContextualTypePredicates1.ts, 1, 12))
>bar : Symbol(bar, Decl(inferContextualTypePredicates1.ts, 1, 25))

declare function skipIf<A, B extends A>(
>skipIf : Symbol(skipIf, Decl(inferContextualTypePredicates1.ts, 1, 40))
>A : Symbol(A, Decl(inferContextualTypePredicates1.ts, 3, 24))
>B : Symbol(B, Decl(inferContextualTypePredicates1.ts, 3, 26))
>A : Symbol(A, Decl(inferContextualTypePredicates1.ts, 3, 24))

as: A[],
>as : Symbol(as, Decl(inferContextualTypePredicates1.ts, 3, 40))
>A : Symbol(A, Decl(inferContextualTypePredicates1.ts, 3, 24))

predicate: (a: A) => a is B,
>predicate : Symbol(predicate, Decl(inferContextualTypePredicates1.ts, 4, 10))
>a : Symbol(a, Decl(inferContextualTypePredicates1.ts, 5, 14))
>A : Symbol(A, Decl(inferContextualTypePredicates1.ts, 3, 24))
>a : Symbol(a, Decl(inferContextualTypePredicates1.ts, 5, 14))
>B : Symbol(B, Decl(inferContextualTypePredicates1.ts, 3, 26))

): Exclude<A, B>[];
>Exclude : Symbol(Exclude, Decl(lib.es5.d.ts, --, --))
>A : Symbol(A, Decl(inferContextualTypePredicates1.ts, 3, 24))
>B : Symbol(B, Decl(inferContextualTypePredicates1.ts, 3, 26))

declare const items: (Foo | Bar)[];
>items : Symbol(items, Decl(inferContextualTypePredicates1.ts, 8, 13))
>Foo : Symbol(Foo, Decl(inferContextualTypePredicates1.ts, 0, 0))
>Bar : Symbol(Bar, Decl(inferContextualTypePredicates1.ts, 0, 40))

const r1 = skipIf(items, (item) => item.type === "foo"); // ok
>r1 : Symbol(r1, Decl(inferContextualTypePredicates1.ts, 10, 5))
>skipIf : Symbol(skipIf, Decl(inferContextualTypePredicates1.ts, 1, 40))
>items : Symbol(items, Decl(inferContextualTypePredicates1.ts, 8, 13))
>item : Symbol(item, Decl(inferContextualTypePredicates1.ts, 10, 26))
>item.type : Symbol(type, Decl(inferContextualTypePredicates1.ts, 0, 12), Decl(inferContextualTypePredicates1.ts, 1, 12))
>item : Symbol(item, Decl(inferContextualTypePredicates1.ts, 10, 26))
>type : Symbol(type, Decl(inferContextualTypePredicates1.ts, 0, 12), Decl(inferContextualTypePredicates1.ts, 1, 12))

const r2 = skipIf(items, (item) => item.type === "foo" || item.type === "bar"); // ok
>r2 : Symbol(r2, Decl(inferContextualTypePredicates1.ts, 11, 5))
>skipIf : Symbol(skipIf, Decl(inferContextualTypePredicates1.ts, 1, 40))
>items : Symbol(items, Decl(inferContextualTypePredicates1.ts, 8, 13))
>item : Symbol(item, Decl(inferContextualTypePredicates1.ts, 11, 26))
>item.type : Symbol(type, Decl(inferContextualTypePredicates1.ts, 0, 12), Decl(inferContextualTypePredicates1.ts, 1, 12))
>item : Symbol(item, Decl(inferContextualTypePredicates1.ts, 11, 26))
>type : Symbol(type, Decl(inferContextualTypePredicates1.ts, 0, 12), Decl(inferContextualTypePredicates1.ts, 1, 12))
>item.type : Symbol(type, Decl(inferContextualTypePredicates1.ts, 1, 12))
>item : Symbol(item, Decl(inferContextualTypePredicates1.ts, 11, 26))
>type : Symbol(type, Decl(inferContextualTypePredicates1.ts, 1, 12))

const r3 = skipIf(items, (item) => false); // ok
>r3 : Symbol(r3, Decl(inferContextualTypePredicates1.ts, 12, 5))
>skipIf : Symbol(skipIf, Decl(inferContextualTypePredicates1.ts, 1, 40))
>items : Symbol(items, Decl(inferContextualTypePredicates1.ts, 8, 13))
>item : Symbol(item, Decl(inferContextualTypePredicates1.ts, 12, 26))

const r4 = skipIf(items, (item) => true); // ok
>r4 : Symbol(r4, Decl(inferContextualTypePredicates1.ts, 13, 5))
>skipIf : Symbol(skipIf, Decl(inferContextualTypePredicates1.ts, 1, 40))
>items : Symbol(items, Decl(inferContextualTypePredicates1.ts, 8, 13))
>item : Symbol(item, Decl(inferContextualTypePredicates1.ts, 13, 26))

const pred1: (a: string | null, b: string | null) => b is string = (a, b) => typeof b === 'string'; // ok
>pred1 : Symbol(pred1, Decl(inferContextualTypePredicates1.ts, 15, 5))
>a : Symbol(a, Decl(inferContextualTypePredicates1.ts, 15, 14))
>b : Symbol(b, Decl(inferContextualTypePredicates1.ts, 15, 31))
>b : Symbol(b, Decl(inferContextualTypePredicates1.ts, 15, 31))
>a : Symbol(a, Decl(inferContextualTypePredicates1.ts, 15, 68))
>b : Symbol(b, Decl(inferContextualTypePredicates1.ts, 15, 70))
>b : Symbol(b, Decl(inferContextualTypePredicates1.ts, 15, 70))

const pred2: (a: string | null, b: string | null) => b is string = (a, b) => typeof a === 'string'; // error
>pred2 : Symbol(pred2, Decl(inferContextualTypePredicates1.ts, 16, 5))
>a : Symbol(a, Decl(inferContextualTypePredicates1.ts, 16, 14))
>b : Symbol(b, Decl(inferContextualTypePredicates1.ts, 16, 31))
>b : Symbol(b, Decl(inferContextualTypePredicates1.ts, 16, 31))
>a : Symbol(a, Decl(inferContextualTypePredicates1.ts, 16, 68))
>b : Symbol(b, Decl(inferContextualTypePredicates1.ts, 16, 70))
>a : Symbol(a, Decl(inferContextualTypePredicates1.ts, 16, 68))

export declare function every<T, U extends T>(array: readonly T[], callback: (element: T, index: number) => element is U): array is readonly U[];
>every : Symbol(every, Decl(inferContextualTypePredicates1.ts, 16, 99), Decl(inferContextualTypePredicates1.ts, 18, 145), Decl(inferContextualTypePredicates1.ts, 19, 169))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 18, 30))
>U : Symbol(U, Decl(inferContextualTypePredicates1.ts, 18, 32))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 18, 30))
>array : Symbol(array, Decl(inferContextualTypePredicates1.ts, 18, 46))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 18, 30))
>callback : Symbol(callback, Decl(inferContextualTypePredicates1.ts, 18, 66))
>element : Symbol(element, Decl(inferContextualTypePredicates1.ts, 18, 78))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 18, 30))
>index : Symbol(index, Decl(inferContextualTypePredicates1.ts, 18, 89))
>element : Symbol(element, Decl(inferContextualTypePredicates1.ts, 18, 78))
>U : Symbol(U, Decl(inferContextualTypePredicates1.ts, 18, 32))
>array : Symbol(array, Decl(inferContextualTypePredicates1.ts, 18, 46))
>U : Symbol(U, Decl(inferContextualTypePredicates1.ts, 18, 32))

export declare function every<T, U extends T>(array: readonly T[] | undefined, callback: (element: T, index: number) => element is U): array is readonly U[] | undefined;
>every : Symbol(every, Decl(inferContextualTypePredicates1.ts, 16, 99), Decl(inferContextualTypePredicates1.ts, 18, 145), Decl(inferContextualTypePredicates1.ts, 19, 169))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 19, 30))
>U : Symbol(U, Decl(inferContextualTypePredicates1.ts, 19, 32))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 19, 30))
>array : Symbol(array, Decl(inferContextualTypePredicates1.ts, 19, 46))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 19, 30))
>callback : Symbol(callback, Decl(inferContextualTypePredicates1.ts, 19, 78))
>element : Symbol(element, Decl(inferContextualTypePredicates1.ts, 19, 90))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 19, 30))
>index : Symbol(index, Decl(inferContextualTypePredicates1.ts, 19, 101))
>element : Symbol(element, Decl(inferContextualTypePredicates1.ts, 19, 90))
>U : Symbol(U, Decl(inferContextualTypePredicates1.ts, 19, 32))
>array : Symbol(array, Decl(inferContextualTypePredicates1.ts, 19, 46))
>U : Symbol(U, Decl(inferContextualTypePredicates1.ts, 19, 32))

export declare function every<T>(array: readonly T[] | undefined, callback: (element: T, index: number) => boolean): boolean;
>every : Symbol(every, Decl(inferContextualTypePredicates1.ts, 16, 99), Decl(inferContextualTypePredicates1.ts, 18, 145), Decl(inferContextualTypePredicates1.ts, 19, 169))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 20, 30))
>array : Symbol(array, Decl(inferContextualTypePredicates1.ts, 20, 33))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 20, 30))
>callback : Symbol(callback, Decl(inferContextualTypePredicates1.ts, 20, 65))
>element : Symbol(element, Decl(inferContextualTypePredicates1.ts, 20, 77))
>T : Symbol(T, Decl(inferContextualTypePredicates1.ts, 20, 30))
>index : Symbol(index, Decl(inferContextualTypePredicates1.ts, 20, 88))

type Type = {
>Type : Symbol(Type, Decl(inferContextualTypePredicates1.ts, 20, 125))

kind: number;
>kind : Symbol(kind, Decl(inferContextualTypePredicates1.ts, 22, 13))

flags: number;
>flags : Symbol(flags, Decl(inferContextualTypePredicates1.ts, 23, 15))

};

function testEvery(typeSet: Type[]) {
>testEvery : Symbol(testEvery, Decl(inferContextualTypePredicates1.ts, 25, 2))
>typeSet : Symbol(typeSet, Decl(inferContextualTypePredicates1.ts, 27, 19))
>Type : Symbol(Type, Decl(inferContextualTypePredicates1.ts, 20, 125))

if (every(typeSet, (t) => t.kind === 1)) {
>every : Symbol(every, Decl(inferContextualTypePredicates1.ts, 16, 99), Decl(inferContextualTypePredicates1.ts, 18, 145), Decl(inferContextualTypePredicates1.ts, 19, 169))
>typeSet : Symbol(typeSet, Decl(inferContextualTypePredicates1.ts, 27, 19))
>t : Symbol(t, Decl(inferContextualTypePredicates1.ts, 28, 22))
>t.kind : Symbol(kind, Decl(inferContextualTypePredicates1.ts, 22, 13))
>t : Symbol(t, Decl(inferContextualTypePredicates1.ts, 28, 22))
>kind : Symbol(kind, Decl(inferContextualTypePredicates1.ts, 22, 13))

return 1;
}
if (every(typeSet, (t) => t.kind === 2)) {
>every : Symbol(every, Decl(inferContextualTypePredicates1.ts, 16, 99), Decl(inferContextualTypePredicates1.ts, 18, 145), Decl(inferContextualTypePredicates1.ts, 19, 169))
>typeSet : Symbol(typeSet, Decl(inferContextualTypePredicates1.ts, 27, 19))
>t : Symbol(t, Decl(inferContextualTypePredicates1.ts, 31, 22))
>t.kind : Symbol(kind, Decl(inferContextualTypePredicates1.ts, 22, 13))
>t : Symbol(t, Decl(inferContextualTypePredicates1.ts, 31, 22))
>kind : Symbol(kind, Decl(inferContextualTypePredicates1.ts, 22, 13))

return 2;
}
return -1;
}

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