equality constraints exposed by patterns mess up constraint inference
When patterns bring (equality) constraints into scope, the inference mechanism for other (unrelated) constraints breaks down.
This is a new problem that appeared between
- ghc-7.7.20121025 and
- ghc-7.7.20121114
I can try to track down the commit if that helps.
Testcase against HEAD attached.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.7 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |