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fix(64974): fix contextual typing for destructured parameter defaults #64978

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09da3d0
fix(64974): fix contextual typing for destructured parameter defaults
a-tarasyuk Oct 27, 2026
667c4f2
add additional tests
a-tarasyuk Oct 27, 2026
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5 changes: 3 additions & 2 deletions tsc/internal/checker/checker.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17219,11 +17219,12 @@ func (c *Checker) checkDeclarationInitializer(declaration *ast.Node, checkMode C
t = c.checkExpressionCachedEx(initializer, checkMode)
}
}
if ast.IsParameterDeclaration(ast.GetRootDeclaration(declaration)) {
root := ast.GetRootDeclaration(declaration)
if ast.IsParameterDeclaration(root) {
name := declaration.Name()
switch name.Kind {
case ast.KindObjectBindingPattern:
if isObjectLiteralType(t) {
if isObjectLiteralType(t) && c.getContextualTypeForVariableLikeDeclaration(root, ContextFlagsNone) == nil {
return c.padObjectLiteralType(t, name)
}
case ast.KindArrayBindingPattern:
Expand Down
99 changes: 98 additions & 1 deletion ...stdata/baselines/reference/compiler/objectBindingPatternDefaultMissingElements.errors.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,24 @@
/main.ts(5,5): error TS7031: Binding element 'required' implicitly has an 'any' type.
/main.ts(10,5): error TS7031: Binding element 'required' implicitly has an 'any' type.
/main.ts(15,5): error TS7031: Binding element 'required' implicitly has an 'any' type.
/main.ts(35,11): error TS2322: Type 'string | undefined' is not assignable to type 'number'.
Type 'undefined' is not assignable to type 'number'.
/main.ts(36,11): error TS2322: Type 'number | undefined' is not assignable to type 'string'.
Type 'undefined' is not assignable to type 'string'.
/main.ts(41,11): error TS2322: Type 'number | undefined' is not assignable to type 'string'.
Type 'undefined' is not assignable to type 'string'.
/main.ts(46,11): error TS2322: Type 'number | undefined' is not assignable to type 'string'.
Type 'undefined' is not assignable to type 'string'.
/main.ts(50,59): error TS2339: Property 'b' does not exist on type '{ a?: number | undefined; }'.
/main.ts(51,11): error TS2322: Type 'number | undefined' is not assignable to type 'string'.
Type 'undefined' is not assignable to type 'string'.
/main.ts(55,11): error TS2322: Type 'number | undefined' is not assignable to type 'string'.
Type 'undefined' is not assignable to type 'string'.
/main.ts(59,11): error TS2322: Type 'number' is not assignable to type 'string'.
/main.ts(68,11): error TS2322: Type 'number | undefined' is not assignable to type 'string'.
Type 'undefined' is not assignable to type 'string'.
/main.ts(72,11): error TS2322: Type 'number | undefined' is not assignable to type 'string'.
Type 'undefined' is not assignable to type 'string'.


==== /unchecked.js (0 errors) ====
Expand Down Expand Up @@ -32,7 +50,7 @@
optional = false,
] = []) => {};

==== /main.ts (3 errors) ====
==== /main.ts (13 errors) ====
import { checkedArray, checkedObject } from "./checked";
import { uncheckedArray, uncheckedObject } from "./unchecked";

Expand Down Expand Up @@ -65,4 +83,83 @@
checkedArray(["value"]);
typedObject({ required: "value" });
typedArray(["value"]);

type F = (input?: { a?: string; b?: number }) => number;
export const f1: F = ({ a, b } = {}) => (a ? 1 : 0) + (b ?? 0);

export const f2: (input: { a?: string; b?: number }) => number = ({ a, b } = {}) => (a ? 1 : 0) + (b ?? 0);

declare function f3(callback: F): void;
f3(({ a, b } = {}) => {
const c: number = a;
~
!!! error TS2322: Type 'string | undefined' is not assignable to type 'number'.
!!! error TS2322: Type 'undefined' is not assignable to type 'number'.
const d: string = b;
~
!!! error TS2322: Type 'number | undefined' is not assignable to type 'string'.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
return 0;
});

export const f4: (input?: { a?: { b?: number } }) => number = ({ a: { b } = {} } = {}) => {
const c: string = b;
~
!!! error TS2322: Type 'number | undefined' is not assignable to type 'string'.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
return b ?? 0;
};

export function f5({ a: { b } = {} }: { a?: { b?: number } }) {
const c: string = b;
~
!!! error TS2322: Type 'number | undefined' is not assignable to type 'string'.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
return b;
}

export const f6: (input?: { a?: number }) => void = ({ a, b } = {}) => {
~
!!! error TS2339: Property 'b' does not exist on type '{ a?: number | undefined; }'.
const c: string = a;
~
!!! error TS2322: Type 'number | undefined' is not assignable to type 'string'.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
};

export const f7: (input?: [{ a?: number }?]) => void = ([{ a } = {}] = []) => {
const b: string = a;
~
!!! error TS2322: Type 'number | undefined' is not assignable to type 'string'.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
};

export const f8: (input?: { [key: string]: number }) => void = ({ a } = {}) => {
const b: string = a;
~
!!! error TS2322: Type 'number' is not assignable to type 'string'.
};

export const f9: (input?: any) => void = ({ a: { b } = {} } = {}) => {
b;
};

declare function f10<T>(value: T, callback: (input?: Partial<T>) => void): void;
f10({ a: 1 }, ({ a } = {}) => {
const b: string = a;
~
!!! error TS2322: Type 'number | undefined' is not assignable to type 'string'.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
});

export const f11: (input?: { a?: number }[]) => void = ([...[{ a } = {}]] = []) => {
const b: string = a;
~
!!! error TS2322: Type 'number | undefined' is not assignable to type 'string'.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
};

export const f12: (input: { a: boolean; b?: string }) => string = ({ a, b } = { a: false }) => `${a}${b}`;

export const f13 = (input: { a?: number; b?: string }[]) => input.map(({ a, b } = {}) => `${a}${b}`);

180 changes: 180 additions & 0 deletions tsc/testdata/baselines/reference/compiler/objectBindingPatternDefaultMissingElements.symbols
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Original file line number Diff line number Diff line change
Expand Up @@ -114,3 +114,183 @@ typedObject({ required: "value" });
typedArray(["value"]);
>typedArray : Symbol(typedArray, Decl(main.ts, 8, 12))

type F = (input?: { a?: string; b?: number }) => number;
>F : Symbol(F, Decl(main.ts, 25, 22))
>input : Symbol(input, Decl(main.ts, 27, 10))
>a : Symbol(a, Decl(main.ts, 27, 19))
>b : Symbol(b, Decl(main.ts, 27, 31))

export const f1: F = ({ a, b } = {}) => (a ? 1 : 0) + (b ?? 0);
>f1 : Symbol(f1, Decl(main.ts, 28, 12))
>F : Symbol(F, Decl(main.ts, 25, 22))
>a : Symbol(a, Decl(main.ts, 28, 23))
>b : Symbol(b, Decl(main.ts, 28, 26))
>a : Symbol(a, Decl(main.ts, 28, 23))
>b : Symbol(b, Decl(main.ts, 28, 26))

export const f2: (input: { a?: string; b?: number }) => number = ({ a, b } = {}) => (a ? 1 : 0) + (b ?? 0);
>f2 : Symbol(f2, Decl(main.ts, 30, 12))
>input : Symbol(input, Decl(main.ts, 30, 18))
>a : Symbol(a, Decl(main.ts, 30, 26))
>b : Symbol(b, Decl(main.ts, 30, 38))
>a : Symbol(a, Decl(main.ts, 30, 67))
>b : Symbol(b, Decl(main.ts, 30, 70))
>a : Symbol(a, Decl(main.ts, 30, 67))
>b : Symbol(b, Decl(main.ts, 30, 70))

declare function f3(callback: F): void;
>f3 : Symbol(f3, Decl(main.ts, 30, 107))
>callback : Symbol(callback, Decl(main.ts, 32, 20))
>F : Symbol(F, Decl(main.ts, 25, 22))

f3(({ a, b } = {}) => {
>f3 : Symbol(f3, Decl(main.ts, 30, 107))
>a : Symbol(a, Decl(main.ts, 33, 5))
>b : Symbol(b, Decl(main.ts, 33, 8))

const c: number = a;
>c : Symbol(c, Decl(main.ts, 34, 9))
>a : Symbol(a, Decl(main.ts, 33, 5))

const d: string = b;
>d : Symbol(d, Decl(main.ts, 35, 9))
>b : Symbol(b, Decl(main.ts, 33, 8))

return 0;
});

export const f4: (input?: { a?: { b?: number } }) => number = ({ a: { b } = {} } = {}) => {
>f4 : Symbol(f4, Decl(main.ts, 39, 12))
>input : Symbol(input, Decl(main.ts, 39, 18))
>a : Symbol(a, Decl(main.ts, 39, 27))
>b : Symbol(b, Decl(main.ts, 39, 33))
>b : Symbol(b, Decl(main.ts, 39, 69))

const c: string = b;
>c : Symbol(c, Decl(main.ts, 40, 9))
>b : Symbol(b, Decl(main.ts, 39, 69))

return b ?? 0;
>b : Symbol(b, Decl(main.ts, 39, 69))

};

export function f5({ a: { b } = {} }: { a?: { b?: number } }) {
>f5 : Symbol(f5, Decl(main.ts, 42, 2))
>a : Symbol(a, Decl(main.ts, 44, 39))
>b : Symbol(b, Decl(main.ts, 44, 25))
>a : Symbol(a, Decl(main.ts, 44, 39))
>b : Symbol(b, Decl(main.ts, 44, 45))

const c: string = b;
>c : Symbol(c, Decl(main.ts, 45, 9))
>b : Symbol(b, Decl(main.ts, 44, 25))

return b;
>b : Symbol(b, Decl(main.ts, 44, 25))
}

export const f6: (input?: { a?: number }) => void = ({ a, b } = {}) => {
>f6 : Symbol(f6, Decl(main.ts, 49, 12))
>input : Symbol(input, Decl(main.ts, 49, 18))
>a : Symbol(a, Decl(main.ts, 49, 27))
>a : Symbol(a, Decl(main.ts, 49, 54))
>b : Symbol(b, Decl(main.ts, 49, 57))

const c: string = a;
>c : Symbol(c, Decl(main.ts, 50, 9))
>a : Symbol(a, Decl(main.ts, 49, 54))

};

export const f7: (input?: [{ a?: number }?]) => void = ([{ a } = {}] = []) => {
>f7 : Symbol(f7, Decl(main.ts, 53, 12))
>input : Symbol(input, Decl(main.ts, 53, 18))
>a : Symbol(a, Decl(main.ts, 53, 28))
>a : Symbol(a, Decl(main.ts, 53, 58))

const b: string = a;
>b : Symbol(b, Decl(main.ts, 54, 9))
>a : Symbol(a, Decl(main.ts, 53, 58))

};

export const f8: (input?: { [key: string]: number }) => void = ({ a } = {}) => {
>f8 : Symbol(f8, Decl(main.ts, 57, 12))
>input : Symbol(input, Decl(main.ts, 57, 18))
>key : Symbol(key, Decl(main.ts, 57, 29))
>a : Symbol(a, Decl(main.ts, 57, 65))

const b: string = a;
>b : Symbol(b, Decl(main.ts, 58, 9))
>a : Symbol(a, Decl(main.ts, 57, 65))

};

export const f9: (input?: any) => void = ({ a: { b } = {} } = {}) => {
>f9 : Symbol(f9, Decl(main.ts, 61, 12))
>input : Symbol(input, Decl(main.ts, 61, 18))
>b : Symbol(b, Decl(main.ts, 61, 48))

b;
>b : Symbol(b, Decl(main.ts, 61, 48))

};

declare function f10<T>(value: T, callback: (input?: Partial<T>) => void): void;
>f10 : Symbol(f10, Decl(main.ts, 63, 2))
>T : Symbol(T, Decl(main.ts, 65, 21))
>value : Symbol(value, Decl(main.ts, 65, 24))
>T : Symbol(T, Decl(main.ts, 65, 21))
>callback : Symbol(callback, Decl(main.ts, 65, 33))
>input : Symbol(input, Decl(main.ts, 65, 45))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>T : Symbol(T, Decl(main.ts, 65, 21))

f10({ a: 1 }, ({ a } = {}) => {
>f10 : Symbol(f10, Decl(main.ts, 63, 2))
>a : Symbol(a, Decl(main.ts, 66, 5))
>a : Symbol(a, Decl(main.ts, 66, 16))

const b: string = a;
>b : Symbol(b, Decl(main.ts, 67, 9))
>a : Symbol(a, Decl(main.ts, 66, 16))

});

export const f11: (input?: { a?: number }[]) => void = ([...[{ a } = {}]] = []) => {
>f11 : Symbol(f11, Decl(main.ts, 70, 12))
>input : Symbol(input, Decl(main.ts, 70, 19))
>a : Symbol(a, Decl(main.ts, 70, 28))
>a : Symbol(a, Decl(main.ts, 70, 62))

const b: string = a;
>b : Symbol(b, Decl(main.ts, 71, 9))
>a : Symbol(a, Decl(main.ts, 70, 62))

};

export const f12: (input: { a: boolean; b?: string }) => string = ({ a, b } = { a: false }) => `${a}${b}`;
>f12 : Symbol(f12, Decl(main.ts, 74, 12))
>input : Symbol(input, Decl(main.ts, 74, 19))
>a : Symbol(a, Decl(main.ts, 74, 27))
>b : Symbol(b, Decl(main.ts, 74, 39))
>a : Symbol(a, Decl(main.ts, 74, 68))
>b : Symbol(b, Decl(main.ts, 74, 71))
>a : Symbol(a, Decl(main.ts, 74, 79))
>a : Symbol(a, Decl(main.ts, 74, 68))
>b : Symbol(b, Decl(main.ts, 74, 71))

export const f13 = (input: { a?: number; b?: string }[]) => input.map(({ a, b } = {}) => `${a}${b}`);
>f13 : Symbol(f13, Decl(main.ts, 76, 12))
>input : Symbol(input, Decl(main.ts, 76, 20))
>a : Symbol(a, Decl(main.ts, 76, 28))
>b : Symbol(b, Decl(main.ts, 76, 40))
>input.map : Symbol(Array.map, Decl(lib.es5.d.ts, --, --))
>input : Symbol(input, Decl(main.ts, 76, 20))
>map : Symbol(Array.map, Decl(lib.es5.d.ts, --, --))
>a : Symbol(a, Decl(main.ts, 76, 72))
>b : Symbol(b, Decl(main.ts, 76, 75))
>a : Symbol(a, Decl(main.ts, 76, 72))
>b : Symbol(b, Decl(main.ts, 76, 75))

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