Expand the tuple contextual type to the target's shape when it comes from a binding pattern #52630
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Andarist
commented
Feb 6, 2023
src/compiler/checker.ts
Outdated
| // this allows us to infer tuples even if the binding pattern is shorter than the target type, like here: | ||
| // declare function fn<T>(t: T) => [T, string[]]; | ||
| // const [[x]] = fn(['hi']); | ||
| else if (isTupleType(contextualType) && isTupleType(inferenceTargetType)) { |
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this doesn't handle the case when inferenceTargetType is a union of tuple types but I have no idea how "expansion" towards that shape should work - unless all union members would have the very same shape
…from a binding pattern
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This seems pretty reasonable to me. @typescript-bot user test this |
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Heya @andrewbranch, I've started to run the diff-based top-repos suite on this PR at cfc350b. You can monitor the build here. Update: The results are in! |
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Heya @andrewbranch, I've started to run the diff-based user code test suite on this PR at cfc350b. You can monitor the build here. Update: The results are in! |
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Heya @andrewbranch, I've started to run the perf test suite on this PR at cfc350b. You can monitor the build here. Update: The results are in! |
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@andrewbranch Here are the results of running the user test suite comparing Everything looks good! |
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@andrewbranch Here are the results of running the top-repos suite comparing Everything looks good! |
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@andrewbranch Here they are:
CompilerComparison Report - main..52630
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TSServerComparison Report - main..52630
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StartupComparison Report - main..52630
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Developer Information: |
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# Conflicts: # tests/baselines/reference/inferTupleFromBindingPattern.js # tests/baselines/reference/inferTupleFromBindingPattern.symbols # tests/baselines/reference/inferTupleFromBindingPattern.types
weswigham
reviewed
Jun 13, 2023
| resultFlags = source.target.elementFlags.slice(); | ||
| } | ||
| const targetFlag = target.target.elementFlags[i]; | ||
| resultTypes.push(anyType); |
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Rather than any with the target flags, shouldn't it be never with the optional flag? To reflect how the consumer never reads the member?
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This gets superseded by #56875 since this PR here aimed to solve the problem through special-casing and the new PR takes a much more general approach to this and similar problems. |
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fixes #42969
cc @andrewbranch