a765333738
During well-formed checking, we walk through all types 'nested' in generic arguments. For example, WF-checking `Option<MyStruct<u8>>` will cause us to check `MyStruct<u8>` and `u8`. However, this is done on a `rustc_middle::ty::Ty`, which has no span information. As a result, any errors that occur will have a very general span (e.g. the definintion of an associated item). This becomes a problem when macros are involved. In general, an associated type like `type MyType = Option<MyStruct<u8>>;` may have completely different spans for each nested type in the HIR. Using the span of the entire associated item might end up pointing to a macro invocation, even though a user-provided span is available in one of the nested types. This PR adds a framework for HIR-based well formed checking. This check is only run during error reporting, and is used to obtain a more precise span for an existing error. This is accomplished by individually checking each 'nested' type in the HIR for the type, allowing us to find the most-specific type (and span) that produces a given error. The majority of the changes are to the error-reporting code. However, some of the general trait code is modified to pass through more information. Since this has no soundness implications, I've implemented a minimal version to begin with, which can be extended over time. In particular, this only works for HIR items with a corresponding `DefId` (e.g. it will not work for WF-checking performed within function bodies). |
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| .. | ||
| keys.rs | ||
| lib.rs | ||
| plumbing.rs | ||
| profiling_support.rs | ||
| README.md | ||
| stats.rs | ||
| values.rs | ||
For more information about how the query system works, see the rustc dev guide.