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soutaro
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Jan 7, 2025
soutaro
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- The length of the tuple types must be same
- Record type with additional key cannot be a subtype of another record type
rhiroe
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Feb 26, 2026
When an array literal appears in an if-branch and the expected return type is a union of tuple types (e.g. [":", ".#"] | [".#", ":"]), the type checker was incorrectly inferring [::String, ::String] instead of the correct literal tuple type. The root cause: #try_tuple_type returns a Pair even when the inferred type doesn't match the given tuple hint. Previously, the first non-nil pair was accepted unconditionally, so ['.#', ':'] tried against hint [":", ".#"] produced [::String, ::String], which was accepted instead of trying the next hint [".#", ":"]. Fix: validate each candidate pair with a subtype check against the specific tuple hint. If no candidate passes the check, fall back to the first candidate (to preserve the FalseAssertion diagnostic for cases like [1, ""] #: [1, "", bool]). Fixes the regression introduced by soutaro#1460 (Strict record and tuple subtyping).
rhiroe
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Feb 26, 2026
When an array literal appears in an if-branch and the expected return type is a union of tuple types (e.g. ["yes", "ok"] | ["no", "error"]), the type checker was incorrectly inferring [::String, ::String] instead of the correct literal tuple type. The root cause: #try_tuple_type returns a Pair even when the inferred type does not match the given tuple hint. Previously, the first non-nil pair was accepted unconditionally, so ["no", "error"] tried against hint ["yes", "ok"] produced [::String, ::String], which was accepted instead of trying the next hint ["no", "error"]. Fix: validate each candidate pair with a subtype check against the specific tuple hint. If no candidate passes the check, fall back to the first candidate (to preserve the FalseAssertion diagnostic for cases like [1, ""] #: [1, "", bool]). Fixes the regression introduced by soutaro#1460 (Strict record and tuple subtyping).
rhiroe
added a commit
to rhiroe/steep
that referenced
this pull request
Feb 26, 2026
When an array literal appears in an if-branch and the expected return type is a union of tuple types (e.g. `["yes", "ok"]` | `["no", "error"]`), the type checker was incorrectly inferring `[::String, ::String]` instead of the correct literal tuple type. The root cause: `#try_tuple_type` returns a `Pair` even when the inferred type does not match the given tuple hint. Previously, the first non-nil pair was accepted unconditionally, so `["no", "error"]` tried against hint `["yes", "ok"]` produced `[::String, ::String]`, which was accepted instead of trying the next hint `["no", "error"]`. Fix: validate each candidate pair with a subtype check against the specific tuple hint. If no candidate passes the check, fall back to the first candidate (to preserve the `FalseAssertion` diagnostic for cases like `[1, ""]` `#: [1, "", bool]`). Fixes the regression introduced by soutaro#1460 (Strict record and tuple subtyping).
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