#4430: Better support for resolving infix expressions in template haskell
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Reporter: reinerp | Owner: igloo
Type: feature request | Status: patch
Priority: normal | Milestone: 7.4.1
Component: Template Haskell | Version: 6.12.3
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by reinerp):
Because our hypothetical quasiquoter doesn't know that it's illegal (you
need to know the operator fixities for that). And even though there is at
most one legal way to resolve the expression {{{(1 + 2 +)}}}, namely to
{{{((1 + 2) +)}}}, it would not be acceptable for our quasiquoter to do
this conversion:
* firstly, this turns some illegal haskell expressions into legal ones,
which in itself is not a huge problem
* more importantly, some (illegal, but plausible) expressions will be
given surprising meanings. For instance, consider {{{(* 2 + 1)}}}. It is
illegal in haskell, but one might think it should mean {{{(\x -> x * 2 +
1)}}}. However, the above conversion would turn it into {{{(* (2 + 1))}}},
which is completely different.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4430#comment:19>
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