Promoted type constructors don't print right in HsType
Consider this
ghci> import Data.Proxy
ghci> undefined :: '() -> Int
<interactive>:11:14: error:
• Expected a type, but ‘ '()’ has kind ‘()’
• In an expression type signature: '() -> IntWhat is that strange space doing before the '()?
Similarly
undefined :: Proxy '() Int
<interactive>:12:14: error:
• Expected kind ‘* -> *’, but ‘Proxy '()’ has kind ‘*’
• In an expression type signature: Proxy '() IntAgain, the strange space.
It comes from the HsType pretty printer, which is worried
about printing the type
'['K]That is, a promoted list with one element K. The trouble is that looks
like a character literal '['.
So we add an extra space, thus '[ 'K]. ''But we add it before every
promoded data constructor!" Hence the spurious spaces.
In IfaceType exactly the same thing happens, but we are more clever,
and only print the leading space if the promoted data con immediately
follows '[ or '(. We should do the same thing for HsType.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.6.2 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |