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| author | Vladislav Zavialov <vlad.z.4096@gmail.com> | 2019-12-02 23:10:33 +0300 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-12-05 16:07:49 -0500 |
| commit | 3354c68ec6c90bbccc0f361aa7973eeb75ea229c (patch) | |
| tree | b9c5e2f9627b25b6d7bdf745b281b6771b8d5990 /testsuite/tests/indexed-types/should_fail/T9171.stderr | |
| parent | c4ca29c796fa86ad9d5cd4dfa1a5cdd4e0565fb0 (diff) | |
| download | haskell-3354c68ec6c90bbccc0f361aa7973eeb75ea229c.tar.gz | |
Pretty-printing of the * kind
Before this patch, GHC always printed the * kind unparenthesized.
This led to two issues:
1. Sometimes GHC printed invalid or incorrect code.
For example, GHC would print: type F @* x = x
when it meant to print: type F @(*) x = x
In the former case, instead of a kind application we were getting a
type operator (@*).
2. Sometimes GHC printed kinds that were correct but hard to read.
Should Either * Int be read as Either (*) Int
or as (*) Either Int ?
This depends on whether -XStarIsType is enabled, but it would be
easier if we didn't have to check for the flag when reading the code.
We can solve both problems by assigning (*) a different precedence. Note
that Haskell98 kinds are not affected:
((* -> *) -> *) -> * does NOT become (((*) -> (*)) -> (*)) -> (*)
The parentheses are added when (*) is used in a function argument
position:
F * * * becomes F (*) (*) (*)
F A * B becomes F A (*) B
Proxy * becomes Proxy (*)
a * -> * becomes a (*) -> *
Diffstat (limited to 'testsuite/tests/indexed-types/should_fail/T9171.stderr')
| -rw-r--r-- | testsuite/tests/indexed-types/should_fail/T9171.stderr | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/testsuite/tests/indexed-types/should_fail/T9171.stderr b/testsuite/tests/indexed-types/should_fail/T9171.stderr index 6567570d46..320a6add8d 100644 --- a/testsuite/tests/indexed-types/should_fail/T9171.stderr +++ b/testsuite/tests/indexed-types/should_fail/T9171.stderr @@ -1,9 +1,9 @@ T9171.hs:10:20: error: • Couldn't match expected type ‘GetParam - @* @k2 @* Base (GetParam @* @* @k2 Base Int)’ + @(*) @k2 @(*) Base (GetParam @(*) @(*) @k2 Base Int)’ with actual type ‘GetParam - @* @k20 @* Base (GetParam @* @* @k20 Base Int)’ + @(*) @k20 @(*) Base (GetParam @(*) @(*) @k20 Base Int)’ NB: ‘GetParam’ is a non-injective type family The type variable ‘k20’ is ambiguous • In the ambiguity check for an expression type signature |