#5763: Confusing error message -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.2.2 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: | Blocked By: None/Unknown | Related Tickets: Test Case: indexed- | types/should_fail/T5763 | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by thomie): Is this problem solved? `T4272` doesn't show the `Occurs check` message anymore (as also noted by SPJ in da71a9524ffff0865222127bef09fd04a1359a53), but maybe this is incidental? I can not find test `T5763` anywhere, so I'll leave this open for now. Output of running the command "git show 0b3c3c81792c88ee40687f86bed4935e721dabe0 testsuite/tests/indexed- types/should_fail/T4272.stderr": {{{ Author: Dimitrios.Vytiniotis <> Date: Wed Apr 4 14:41:11 2012 +0100 Error message modifications following ghc-new-solver modifications diff --git a/testsuite/tests/indexed-types/should_fail/T4272.stderr b/testsuite/tests/indexed-types/should_fail/T4272.stderr index 24f0cbd..e809d9c 100644 --- a/testsuite/tests/indexed-types/should_fail/T4272.stderr +++ b/testsuite/tests/indexed-types/should_fail/T4272.stderr @@ -1,29 +1,6 @@ -T4272.hs:11:16: - Couldn't match type `TermFamily (TermFamily x0 x0)' - with `TermFamily x0' - NB: `TermFamily' is a type function, and may not be injective - The type variable `x0' is ambiguous - Possible fix: add a type signature that fixes these type variable(s) - Expected type: TermFamily x0 x0 - Actual type: TermFamily a a - In the first argument of `prune', namely `t' - In the expression: prune t (terms (undefined :: TermFamily a a)) - In an equation for `laws': - laws t = prune t (terms (undefined :: TermFamily a a)) - -T4272.hs:11:16: - Occurs check: cannot construct the infinite type: - x0 = TermFamily x0 x0 - Expected type: TermFamily x0 x0 - Actual type: TermFamily a a - In the first argument of `prune', namely `t' - In the expression: prune t (terms (undefined :: TermFamily a a)) - In an equation for `laws': - laws t = prune t (terms (undefined :: TermFamily a a)) - -T4272.hs:11:19: - Could not deduce (a ~ TermFamily x0 x0) +T4272.hs:11:26: + Could not deduce (a ~ TermFamily a a) from the context (TermLike a) bound by the type signature for laws :: TermLike a => TermFamily a a -> b @@ -31,7 +8,10 @@ T4272.hs:11:19: `a' is a rigid type variable bound by the type signature for laws :: TermLike a => TermFamily a a -> b at T4272.hs:10:16 - In the return type of a call of `terms' + Expected type: TermFamily a (TermFamily a a) + Actual type: TermFamily a a + In the first argument of `terms', namely + `(undefined :: TermFamily a a)' In the second argument of `prune', namely `(terms (undefined :: TermFamily a a))' In the expression: prune t (terms (undefined :: TermFamily a a)) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/5763#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler