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Re-add undefined assignability check #53561

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Re-add undefined assignability check #53561

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ecbd96e
Re-add assignability check
Mar 28, 2023
0e2b261
Update baseline
Mar 28, 2023
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6 changes: 3 additions & 3 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -35664,8 +35664,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
const functionFlags = getFunctionFlags(func);
const type = returnType && unwrapReturnType(returnType, functionFlags);

// Functions with an explicitly specified 'undefined, 'void', 'any' or 'unknown' return type don't need any return expressions.
if (type && maybeTypeOfKind(type, TypeFlags.Undefined | TypeFlags.Void | TypeFlags.Any | TypeFlags.Unknown)) {
// Functions with an explicitly specified 'undefined, 'void' or 'any' return type don't need any return expressions.
if (type && maybeTypeOfKind(type, TypeFlags.Undefined | TypeFlags.Void | TypeFlags.Any)) {
return;
}

Expand All @@ -35691,7 +35691,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
error(errorNode, Diagnostics.A_function_whose_declared_type_is_neither_void_nor_any_must_return_a_value);
}
}
else if (type && strictNullChecks) {
else if (type && strictNullChecks && !isTypeAssignableTo(undefinedType, type)) {
error(errorNode, Diagnostics.Function_lacks_ending_return_statement_and_return_type_does_not_include_undefined);
}
else if (compilerOptions.noImplicitReturns) {
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5 changes: 4 additions & 1 deletion tests/baselines/reference/unknownType1.errors.txt
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Expand Up @@ -20,14 +20,15 @@ tests/cases/conformance/types/unknown/unknownType1.ts(128,5): error TS2322: Type
tests/cases/conformance/types/unknown/unknownType1.ts(129,5): error TS2322: Type 'number' is not assignable to type '{ [x: string]: unknown; }'.
tests/cases/conformance/types/unknown/unknownType1.ts(143,29): error TS2698: Spread types may only be created from object types.
tests/cases/conformance/types/unknown/unknownType1.ts(144,29): error TS2698: Spread types may only be created from object types.
tests/cases/conformance/types/unknown/unknownType1.ts(150,17): error TS2847: A function whose declared type is neither 'undefined', 'void', nor 'any' must return a value.
tests/cases/conformance/types/unknown/unknownType1.ts(156,14): error TS2700: Rest types may only be created from object types.
tests/cases/conformance/types/unknown/unknownType1.ts(162,5): error TS2564: Property 'a' has no initializer and is not definitely assigned in the constructor.
tests/cases/conformance/types/unknown/unknownType1.ts(170,9): error TS2322: Type 'T' is not assignable to type '{}'.
tests/cases/conformance/types/unknown/unknownType1.ts(171,9): error TS2322: Type 'U' is not assignable to type '{}'.
tests/cases/conformance/types/unknown/unknownType1.ts(181,5): error TS2322: Type 'T' is not assignable to type '{}'.


==== tests/cases/conformance/types/unknown/unknownType1.ts (26 errors) ====
==== tests/cases/conformance/types/unknown/unknownType1.ts (27 errors) ====
// In an intersection everything absorbs unknown

type T00 = unknown & null; // null
Expand Down Expand Up @@ -221,6 +222,8 @@ tests/cases/conformance/types/unknown/unknownType1.ts(181,5): error TS2322: Type
// Functions with unknown return type don't need return expressions

function f27(): unknown {
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Just to be sure: This error should be emitted because noImplicitReturns is true by default right?

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Actually no, this error is issued regardless of noImplicitReturns. It occurs when there are no return statements at all in the function body (i.e. when hasExplicitReturn is false).

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Got it.

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Wait then this comment is incorrect.

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I'm so confused. Can we get a playground link of what was desirable in TS 5.0, but is now incorrect in nightly?

~~~~~~~
!!! error TS2847: A function whose declared type is neither 'undefined', 'void', nor 'any' must return a value.
}

// Rest type cannot be created from unknown
Expand Down