Fix misattributed type inference error span for index expressions#156885
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Fix misattributed type inference error span for index expressions#156885Dnreikronos wants to merge 1 commit into
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When an index expression with an ambiguous type (e.g. `arr[idx.into()]`) appears inside a cast or binary operation, the type inference error was incorrectly attributed to the outer expression instead of the `.into()` call. Resolve the index sub-expression type first so the error points at the actual ambiguous site.
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If
arr[idx.into()]appears inside a cast or binary op, the type inference error gets blamed on the wrong expression.Before:
[1, 2, 3][bad_idx.into()] as i32→ error points at[1, 2, 3][bad_idx.into()](the whole indexing expr)0 + [1, 2, 3][bad_idx.into()]→ error points at+After:
.into(), which is where the ambiguity actually is.In
cast.rs, before resolving the cast expression type, we check if it's an index with an unresolved index type. If so, resolve the index sub-expression first at its own span so the error lands there. If that already errored, skip the broader resolution to avoid duplicates.In
op.rs, after writing the method call for an overloaded binary op, if the return type still has inference variables and the RHS is an index expression, force resolution of the index type at its span.Fixes #156738
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