Add class/context information to typed hole relevant bindings
GHC's typed hole messages don't currently include any known context information for relevant bindings. For example:
bar :: a ~ b => a -> b -> Int
bar x y = _gets me
Found hole ‘_’ with type: Int
Relevant bindings include
y :: b (bound at <interactive>:8:42)
x :: a (bound at <interactive>:8:40)
bar :: a -> b -> Int (bound at <interactive>:8:36)
In the expression: _
In an equation for ‘bar’: bar x y = _The types a and b are not unified, and the a ~ b constraint is not shown.
foo :: Show a => a -> Int
foo x = _gets me
Found hole ‘_’ with type: Int
Relevant bindings include
x :: a (bound at <interactive>:4:36)
foo :: a -> Int (bound at <interactive>:4:32)
In the expression: _
In an equation for ‘foo’: foo x = _The Show constraint is lost.
What I want
I'd like context information for all type variables in known bindings, so I can see all the pieces available to help me fill in the hole.
Related ticket
In #9479 (closed), Dominique Devriese wants to see any constraints on an ambiguously-typed hole.
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 | |
| BlockedBy | |
| Related | #9479 (closed) |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |