#6060: the 'impossible' happened
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Reporter: lerkok | Owner:
Type: bug | Status: patch
Priority: normal | Milestone: 7.6.1
Component: Compiler | Version: 7.4.1
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: Compile-time crash
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by simonpj@…):
commit 67c793a3a13482bc897810e3b5e13f96942afc68
{{{
Author: Simon Peyton Jones <[email protected]>
Date: Tue May 1 08:07:52 2012 +0100
Tidy up a remaining glitch in unification
There was one place, in type checking parallel list comprehensions
where we were unifying types, but had no convenient way to use the
resulting coercion; instead we just checked that it was Refl. This
was Wrong Wrong; it might fail unpredicably in a GADT-like situation,
and it led to extra error-generation code used only in this one place.
This patch tidies it all up, by moving the 'return' method from the
*comprehension* to the ParStmtBlock. The latter is a new data type,
now used for each sub-chunk of a parallel list comprehension.
Because of the data type change, quite a few modules are touched,
but only in a fairly trivial way. The real changes are in TcMatches
(and corresponding desugaring); plus deleting code from TcUnify.
This patch also fixes the pretty-printing bug in Trac #6060
compiler/deSugar/Coverage.lhs | 14 ++++----
compiler/deSugar/DsArrows.lhs | 4 +-
compiler/deSugar/DsListComp.lhs | 39 ++++++++++-----------
compiler/hsSyn/Convert.lhs | 4 +-
compiler/hsSyn/HsExpr.lhs | 33 ++++++++++++------
compiler/hsSyn/HsUtils.lhs | 12 +++---
compiler/main/HscMain.hs | 4 +-
compiler/parser/Parser.y.pp | 3 +-
compiler/rename/RnExpr.lhs | 29 +++++++--------
compiler/typecheck/TcErrors.lhs | 8 ----
compiler/typecheck/TcHsSyn.lhs | 23 ++++++------
compiler/typecheck/TcMatches.lhs | 70
++++++++++----------------------------
compiler/typecheck/TcUnify.lhs | 11 ------
13 files changed, 104 insertions(+), 150 deletions(-)
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6060#comment:3>
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