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Speed up record inclusion check. #6289

Merged
merged 4 commits into from
Jun 7, 2023
Merged

Speed up record inclusion check. #6289

merged 4 commits into from
Jun 7, 2023

Commits on Jun 7, 2023

  1. Speed up record inclusion check. 

    Speed up record inclusion check.
Fixes #6284

Record inclusion check (between implementation and interface) is quadratic.

Example:
```res
module M : {
  type t<'a, 'b, 'c> = {x:list<('a, 'b)>, y:int, z:int}
} = {
  type t<'a, 'b, 'c> = {x:list<('a, 'c)>, y:int, z:int}
}
```

The algorithm tries to instantiate type parameters. It only reports an error if there is an inconsistency. This requires solving type equations involving many types at once.

To improve error message, the first problematic field is reported. So the type equations are checked again and again with size 1, 2, ...n where n is the number of fields. (Plus the type parameters).

This is quadratic and is problematic for types of ~1K elements.

This PR provides a fast path which just checks if there is an error, without blaming a specific field.
The fast path is linear.
Only if an error is detected, the quadratic path is take to blame precisely which field is involved.
    @cristianoc
    cristianoc committed Jun 7, 2023
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  2. Add text for record inclusion. 

    So that there's some minimal sanity check that record type inclusion works as expected on a nontrivial case.
    @cristianoc
    cristianoc committed Jun 7, 2023
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  3. Update CHANGELOG.md

    @cristianoc
    cristianoc committed Jun 7, 2023
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  4. Refactor into a single function.

    @cristianoc
    cristianoc committed Jun 7, 2023
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