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 |