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Compute flow types for function declarations #58411

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Compute flow types for function declarations #58411

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6 changes: 3 additions & 3 deletions src/compiler/checker.ts
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Expand Up @@ -29393,9 +29393,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {

const isAlias = localOrExportSymbol.flags & SymbolFlags.Alias;

// We only narrow variables and parameters occurring in a non-assignment position. For all other
// We only narrow variables, parameters and functions occurring in a non-assignment position. For all other
// entities we simply return the declared type.
Comment on lines +29396 to 29397
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tbf... if this is something the plan would like to pull in, we probably should enable narrowing on just anything. asserts make it possible to expand all non-nullable types

if (localOrExportSymbol.flags & SymbolFlags.Variable) {
if (localOrExportSymbol.flags & (SymbolFlags.Variable | SymbolFlags.Function)) {
if (assignmentKind === AssignmentKind.Definite) {
return isInCompoundLikeAssignment(node) ? getBaseTypeOfLiteralType(type) : type;
}
Expand Down Expand Up @@ -29443,7 +29443,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
// We only look for uninitialized variables in strict null checking mode, and only when we can analyze
// the entire control flow graph from the variable's declaration (i.e. when the flow container and
// declaration container are the same).
const assumeInitialized = isParameter || isAlias || isOuterVariable || isSpreadDestructuringAssignmentTarget || isModuleExports || isSameScopedBindingElement(node, declaration) ||
const assumeInitialized = localOrExportSymbol.flags & SymbolFlags.Function || isParameter || isAlias || isOuterVariable || isSpreadDestructuringAssignmentTarget || isModuleExports || isSameScopedBindingElement(node, declaration) ||
type !== autoType && type !== autoArrayType && (!strictNullChecks || (type.flags & (TypeFlags.AnyOrUnknown | TypeFlags.Void)) !== 0 ||
isInTypeQuery(node) || isInAmbientOrTypeNode(node) || node.parent.kind === SyntaxKind.ExportSpecifier) ||
node.parent.kind === SyntaxKind.NonNullExpression ||
Expand Down
65 changes: 65 additions & 0 deletions tests/baselines/reference/assertionTypePredicatesOnFunction1.symbols
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@@ -0,0 +1,65 @@
//// [tests/cases/conformance/controlFlow/assertionTypePredicatesOnFunction1.ts] ////

=== assertionTypePredicatesOnFunction1.ts ===
// https://github.com/microsoft/TypeScript/issues/41232

interface LabelledFunction {
>LabelledFunction : Symbol(LabelledFunction, Decl(assertionTypePredicatesOnFunction1.ts, 0, 0))

label: string;
>label : Symbol(LabelledFunction.label, Decl(assertionTypePredicatesOnFunction1.ts, 2, 28))
}

declare function assignLabel<T extends (...args: never) => unknown>(
>assignLabel : Symbol(assignLabel, Decl(assertionTypePredicatesOnFunction1.ts, 4, 1))
>T : Symbol(T, Decl(assertionTypePredicatesOnFunction1.ts, 6, 29))
>args : Symbol(args, Decl(assertionTypePredicatesOnFunction1.ts, 6, 40))

fn: T,
>fn : Symbol(fn, Decl(assertionTypePredicatesOnFunction1.ts, 6, 68))
>T : Symbol(T, Decl(assertionTypePredicatesOnFunction1.ts, 6, 29))

label: string,
>label : Symbol(label, Decl(assertionTypePredicatesOnFunction1.ts, 7, 8))

): asserts fn is T & LabelledFunction;
>fn : Symbol(fn, Decl(assertionTypePredicatesOnFunction1.ts, 6, 68))
>T : Symbol(T, Decl(assertionTypePredicatesOnFunction1.ts, 6, 29))
>LabelledFunction : Symbol(LabelledFunction, Decl(assertionTypePredicatesOnFunction1.ts, 0, 0))

function a() {}
>a : Symbol(a, Decl(assertionTypePredicatesOnFunction1.ts, 9, 38))

assignLabel(a, "a");
>assignLabel : Symbol(assignLabel, Decl(assertionTypePredicatesOnFunction1.ts, 4, 1))
>a : Symbol(a, Decl(assertionTypePredicatesOnFunction1.ts, 9, 38))

a.label;
>a.label : Symbol(LabelledFunction.label, Decl(assertionTypePredicatesOnFunction1.ts, 2, 28))
>a : Symbol(a, Decl(assertionTypePredicatesOnFunction1.ts, 9, 38))
>label : Symbol(LabelledFunction.label, Decl(assertionTypePredicatesOnFunction1.ts, 2, 28))

const b = function () {};
>b : Symbol(b, Decl(assertionTypePredicatesOnFunction1.ts, 15, 5))

assignLabel(b, "b");
>assignLabel : Symbol(assignLabel, Decl(assertionTypePredicatesOnFunction1.ts, 4, 1))
>b : Symbol(b, Decl(assertionTypePredicatesOnFunction1.ts, 15, 5))

b.label;
>b.label : Symbol(LabelledFunction.label, Decl(assertionTypePredicatesOnFunction1.ts, 2, 28))
>b : Symbol(b, Decl(assertionTypePredicatesOnFunction1.ts, 15, 5))
>label : Symbol(LabelledFunction.label, Decl(assertionTypePredicatesOnFunction1.ts, 2, 28))

const c = () => {};
>c : Symbol(c, Decl(assertionTypePredicatesOnFunction1.ts, 19, 5))

assignLabel(c, "c");
>assignLabel : Symbol(assignLabel, Decl(assertionTypePredicatesOnFunction1.ts, 4, 1))
>c : Symbol(c, Decl(assertionTypePredicatesOnFunction1.ts, 19, 5))

c.label;
>c.label : Symbol(LabelledFunction.label, Decl(assertionTypePredicatesOnFunction1.ts, 2, 28))
>c : Symbol(c, Decl(assertionTypePredicatesOnFunction1.ts, 19, 5))
>label : Symbol(LabelledFunction.label, Decl(assertionTypePredicatesOnFunction1.ts, 2, 28))

97 changes: 97 additions & 0 deletions tests/baselines/reference/assertionTypePredicatesOnFunction1.types
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@@ -0,0 +1,97 @@
//// [tests/cases/conformance/controlFlow/assertionTypePredicatesOnFunction1.ts] ////

=== assertionTypePredicatesOnFunction1.ts ===
// https://github.com/microsoft/TypeScript/issues/41232

interface LabelledFunction {
label: string;
>label : string
> : ^^^^^^
}

declare function assignLabel<T extends (...args: never) => unknown>(
>assignLabel : <T extends (...args: never) => unknown>(fn: T, label: string) => asserts fn is T & LabelledFunction
> : ^ ^^^^^^^^^^^^^ ^^ ^^^^^ ^^ ^^ ^^ ^^ ^^^^^
>args : never
> : ^^^^^

fn: T,
>fn : T
> : ^

label: string,
>label : string
> : ^^^^^^

): asserts fn is T & LabelledFunction;

function a() {}
>a : () => void
> : ^^^^^^^^^^

assignLabel(a, "a");
>assignLabel(a, "a") : void
> : ^^^^
>assignLabel : <T extends (...args: never) => unknown>(fn: T, label: string) => asserts fn is T & LabelledFunction
> : ^ ^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>a : () => void
> : ^^^^^^^^^^
>"a" : "a"
> : ^^^

a.label;
>a.label : string
> : ^^^^^^
>a : (() => void) & LabelledFunction
> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>label : string
> : ^^^^^^

const b = function () {};
>b : () => void
> : ^^^^^^^^^^
>function () {} : () => void
> : ^^^^^^^^^^

assignLabel(b, "b");
>assignLabel(b, "b") : void
> : ^^^^
>assignLabel : <T extends (...args: never) => unknown>(fn: T, label: string) => asserts fn is T & LabelledFunction
> : ^ ^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>b : () => void
> : ^^^^^^^^^^
>"b" : "b"
> : ^^^

b.label;
>b.label : string
> : ^^^^^^
>b : (() => void) & LabelledFunction
> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>label : string
> : ^^^^^^

const c = () => {};
>c : () => void
> : ^^^^^^^^^^
>() => {} : () => void
> : ^^^^^^^^^^

assignLabel(c, "c");
>assignLabel(c, "c") : void
> : ^^^^
>assignLabel : <T extends (...args: never) => unknown>(fn: T, label: string) => asserts fn is T & LabelledFunction
> : ^ ^^^^^^^^^^^^^ ^^ ^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>c : () => void
> : ^^^^^^^^^^
>"c" : "c"
> : ^^^

c.label;
>c.label : string
> : ^^^^^^
>c : (() => void) & LabelledFunction
> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>label : string
> : ^^^^^^

7 changes: 6 additions & 1 deletion tests/baselines/reference/uncalledFunctionChecksInConditional.errors.txt
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Expand Up @@ -2,14 +2,16 @@ uncalledFunctionChecksInConditional.ts(5,5): error TS2774: This condition will a
uncalledFunctionChecksInConditional.ts(9,5): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
uncalledFunctionChecksInConditional.ts(9,14): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
uncalledFunctionChecksInConditional.ts(13,5): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
uncalledFunctionChecksInConditional.ts(13,14): error TS2349: This expression is not callable.
Type 'never' has no call signatures.
uncalledFunctionChecksInConditional.ts(32,10): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
uncalledFunctionChecksInConditional.ts(36,5): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
uncalledFunctionChecksInConditional.ts(40,22): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
uncalledFunctionChecksInConditional.ts(44,16): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
uncalledFunctionChecksInConditional.ts(48,22): error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?


==== uncalledFunctionChecksInConditional.ts (9 errors) ====
==== uncalledFunctionChecksInConditional.ts (10 errors) ====
declare function isFoo(): boolean;
declare function isBar(): boolean;
declare const isUndefinedFoo: (() => boolean) | undefined;
Expand All @@ -31,6 +33,9 @@ uncalledFunctionChecksInConditional.ts(48,22): error TS2774: This condition will
if (isFoo || isFoo()) {
~~~~~
!!! error TS2774: This condition will always return true since this function is always defined. Did you mean to call it instead?
~~~~~
!!! error TS2349: This expression is not callable.
!!! error TS2349: Type 'never' has no call signatures.
// error on isFoo
}

Expand Down
8 changes: 4 additions & 4 deletions tests/baselines/reference/uncalledFunctionChecksInConditional.types
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Expand Up @@ -36,10 +36,10 @@ if (isFoo || isFoo()) {
> : ^^^^^^^^^^^^^
>isFoo : () => boolean
> : ^^^^^^^^^^^^^
>isFoo() : boolean
> : ^^^^^^^
>isFoo : () => boolean
> : ^^^^^^^^^^^^^
>isFoo() : any
> : ^^^
>isFoo : never
> : ^^^^^

// error on isFoo
}
Expand Down
25 changes: 25 additions & 0 deletions tests/cases/conformance/controlFlow/assertionTypePredicatesOnFunction1.ts
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@@ -0,0 +1,25 @@
// @strict: true
// @noEmit: true

// https://github.com/microsoft/TypeScript/issues/41232

interface LabelledFunction {
label: string;
}

declare function assignLabel<T extends (...args: never) => unknown>(
fn: T,
label: string,
): asserts fn is T & LabelledFunction;

function a() {}
assignLabel(a, "a");
a.label;

const b = function () {};
assignLabel(b, "b");
b.label;

const c = () => {};
assignLabel(c, "c");
c.label;