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| author | Edward Z. Yang <ezyang@cs.stanford.edu> | 2016-10-28 17:54:36 -0700 |
|---|---|---|
| committer | Edward Z. Yang <ezyang@cs.stanford.edu> | 2016-11-16 21:31:59 -0800 |
| commit | 31398fbc6d9ee0bd95de64b08becc38faf188972 (patch) | |
| tree | 0ae632f650671447b96ce231781240b4d840097f /compiler/typecheck/TcBinds.hs | |
| parent | b76958671cda1df9f6f0e1d54d681144d09cb06e (diff) | |
| download | haskell-31398fbc6d9ee0bd95de64b08becc38faf188972.tar.gz | |
Test for type synonym loops on TyCon.
Summary:
Previously, we tested for type synonym loops by doing
a syntactic test on the literal type synonym declarations.
However, in some cases, loops could go through hs-boot
files, leading to an infinite loop (#12042); a similar
situation can occur when signature merging.
This commit replaces the syntactic test with a test on
TyCon, simply by walking down all type synonyms until
we bottom out, or find we've looped back. It's a lot
simpler.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
Test Plan: validate
Reviewers: simonpj, austin, bgamari
Subscribers: goldfire, thomie
Differential Revision: https://phabricator.haskell.org/D2656
GHC Trac Issues: #12042
Diffstat (limited to 'compiler/typecheck/TcBinds.hs')
| -rw-r--r-- | compiler/typecheck/TcBinds.hs | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/compiler/typecheck/TcBinds.hs b/compiler/typecheck/TcBinds.hs index 09746d3cba..60ef82671c 100644 --- a/compiler/typecheck/TcBinds.hs +++ b/compiler/typecheck/TcBinds.hs @@ -1134,7 +1134,9 @@ tcMonoBinds is_rec sig_fn no_gen -- Single function binding, | NonRecursive <- is_rec -- ...binder isn't mentioned in RHS , Nothing <- sig_fn name -- ...with no type signature - = -- In this very special case we infer the type of the + = -- Note [Single function non-recursive binding special-case] + -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + -- In this very special case we infer the type of the -- right hand side first (it may have a higher-rank type) -- and *then* make the monomorphic Id for the LHS -- e.g. f = \(x::forall a. a->a) -> <body> |