Allow implicit return with explicit undefined return type
#53092
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The TypeScript team hasn't accepted the linked issue #36288. If you can get it accepted, this PR will have a better chance of being reviewed. |
saschanaz
commented
Mar 4, 2023
| // Fine since are typed any. | ||
| return; | ||
| } | ||
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| function f9(): void { | ||
| function f9(): any { | ||
| // Fine since we are typed any and return undefined |
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(To match the comments, as otherwise these two are exactly same with f5 and f6.)
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tests/baselines/reference/functionsMissingReturnStatementsAndExpressions.errors.txt
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There's this check below your code else if (type && strictNullChecks && !isTypeAssignableTo(undefinedType, type)) {
error(errorNode, Diagnostics.Function_lacks_ending_return_statement_and_return_type_does_not_include_undefined);
}Do we need the assignability check anymore? - else if (type && strictNullChecks && !isTypeAssignableTo(undefinedType, type)) {
+ else if (type && strictNullChecks) {
error(errorNode, Diagnostics.Function_lacks_ending_return_statement_and_return_type_does_not_include_undefined);
} |
…xpressions.errors.txt Co-authored-by: Daniel Rosenwasser <[email protected]>
jakebailey
reviewed
Mar 6, 2023
| // Okay; return type allows implicit return of undefined | ||
| } | ||
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| function f23(): undefined | number { |
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I think your last commit only included this baseline, as f23 doesn't appear to be anywhere else.
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I just tapped the commit button from GitHub, will add it with the another change for the feedback.
I'm not sure, isn't that for some different situation, as there's still a test for that: TypeScript/tests/cases/compiler/getterControlFlowStrictNull.ts Lines 3 to 11 in 79ef86f |
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You're saying that TypeScript no longer issues an error in that test if you remove that assignability check? I can't see why that would happen. |
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saschanaz
commented
Mar 6, 2023
jakebailey
requested changes
Mar 17, 2023
src/compiler/diagnosticMessages.json
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| @@ -1868,7 +1868,7 @@ | |||
| "category": "Error", | |||
| "code": 2354 | |||
| }, | |||
| "A function whose declared type is neither 'void' nor 'any' must return a value.": { | |||
| "A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.": { | |||
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I think I'd rather us duplicate this message to have two (@DanielRosenwasser may be able to better write these):
A function whose declared type is neither 'void' nor 'any' must return a value.
A function whose declared type is not 'void', 'any', or 'undefined' must return a value.
Then, conditionally emit one based on the variable strictNullChecks.
Then below in codefixes/returnValueCorrect.ts, handle both.
jakebailey
approved these changes
Mar 17, 2023
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LGTM but deferring to @DanielRosenwasser for diagnostic wording.
DanielRosenwasser
approved these changes
Mar 17, 2023
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ahejlsberg
reviewed
Mar 28, 2023
| } | ||
| else if (type && strictNullChecks && !isTypeAssignableTo(undefinedType, type)) { | ||
| else if (type && strictNullChecks) { |
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@jakebailey @DanielRosenwasser The removal of this assignability check has caused a regression. This example now errors when it shouldn't:
function fx2(x: boolean): unknown {
if (x) {
return "hello";
}
};There was a problem hiding this comment.
I noticed the regression here: #53515 (comment)
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Funny. We were just talking about adding this check back again in #53490
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I'll look into why it's not working as we expected.
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Oh, no, that PR was exactly to fix the issue you mentioned. So it should be fixed in main now.
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Checked, and it is fixed, yep.
This was referenced Mar 28, 2023
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Fixes #36288