#5910: Holes with other constraints
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Reporter: xnyhps | Owner:
Type: feature request | Status: new
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 7.5
Keywords: holes | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: Other
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Changes (by spl):
* failure: Incorrect warning at compile-time => Other
Comment:
If {{{-XHoles}}} is set, we want the following:
* The program should be type-checked as if every hole {{{_?h}}} is
replaced by {{{undefined}}}, except:
* If type-checking would fail due to unsolved constraints that could
be solved by giving a type to a hole.
* If the program is well-typed, then:
* The types of all holes should be reported.
* Reporting the hole types should not cause type-checking (or
compiling in general) to stop (in error).
* (optional) If the program is ill-typed, then:
* The types of all holes should be reported.
The above should hold true with and without the monomorphism restriction.
In particular, if an {{{undefined}}} somewhere in a program type-checked
with the monomorphism restriction would cause type-checking to fail, then
a hole in that same position should also cause type-checking to fail.
The type of a hole should be the resolved type with minimum constraints.
That is, the type of a hole should only have constraints that have not be
solved but are either inferred from the context (e.g. {{{show _?h}}}) or
given in a type annotation/signature (e.g. {{{_?h :: Show a => a}}}.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5910#comment:12>
GHC <http://www.haskell.org/ghc/>
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