Give strong preference to type variable names in scope when reporting hole contexts
When using ScopedTypeVariables
with typed holes, I want GHC to bend over backwards to preserve the names of type variables that the user has chosen to bring into scope. I can't immediately reproduce the situations I've run into recently where that hasn't happened, but sometimes I've had a signature like
foo :: forall bar . ...
foo = ... _ ...
and yet the typed hole message shows that bar
has been lost in unification and replaced by some unrelated name. I would very much prefer if this never happened.
Trac metadata
Trac field | Value |
---|---|
Version | 7.10.2 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
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Blocking | |
CC | |
Operating system | |
Architecture |