microsoft/pyright
1
1
Fork 0
mirror of https://github.com/microsoft/pyright.git synced 2024-08-16 11:20:22 +03:00
Code Issues Projects Releases Wiki Activity

Further clarified the new overload behavior in the documentation.

Browse Source
This commit is contained in:
Eric Traut 2022-12-18 08:06:47 -08:00
parent c9e43d2594
commit 8d3a6e62c8
1 changed files with 3 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
docs/type-concepts.md
View File

@ -410,7 +410,9 @@ Some functions or methods can return one of several different types. In cases wh
3. If only one overload remains, it is the “winner”.
4. If more than one overload remains, the “winner” is chosen based on the order in which the overloads are declared. In general, the first remaining overload is the “winner”. One exception to this rule is when a `*args` (unpacked) argument matches a `*args` parameter in one of the overload signatures. This situation overrides the normal order-based rule. Another exception is when two or more overloads match because an argument evaluates to `Any` or `Unknown`. In this situation, the matching overload is ambiguous, so the call expression evaluates to `Unknown`.
4. If more than one overload remains, the “winner” is chosen based on the order in which the overloads are declared. In general, the first remaining overload is the “winner”. There are two exceptions to this rule.
Exception 1: When an `*args` (unpacked) argument matches a `*args` parameter in one of the overload signatures, this overrides the normal order-based rule.
Exception 2: When two or more overloads match because an argument evaluates to `Any` or `Unknown`, the matching overload is ambiguous. In this case, pyright examines the return types of the remaining overloads and eliminates types that are duplicates or are subsumed by (i.e. proper subtypes of) other types in the list. If only one type remains after this coalescing step, that type is used. If more than one type remains after this coalescing step, the type of the call expression evaluates to `Unknown`. For example, if two overloads are matched due to an argument that evaluates to `Any`, and those two overloads have return types of `str` and `LiteralString`, pyright will coalesce this to just `str` because `LiteralString` is a proper subtype of `str`. If the two overloads have return types of `str` and `bytes`, the call expression will evaluate to `Unknown` because `str` and `bytes` have no overlap.
5. If no overloads remain, Pyright considers whether any of the arguments are union types. If so, these union types are expanded into their constituent subtypes, and the entire process of overload matching is repeated with the expanded argument types. If two or more overloads match, the union of their respective return types form the final return type for the call expression.