infix precedence of backtick functions defined in ghci is not reported by :info

[EyalLotem]

excerpt from ghci:

Prelude> let infixr 9 `f` ; f = (+)
let infixr 9 `f` ; f = (+)
Prelude> 5 * 3 `f` 4
35
Prelude> :info f
f :: Integer -> Integer -> Integer
  	-- Defined at <interactive>:1:19
Prelude> :info `f`
f :: Integer -> Integer -> Integer
  	-- Defined at <interactive>:1:19

[EyalLotem]

In fact, the bug is more severe, the infix declaration in ghci is not used at all:

Prelude> let infixr 0 `f` ; f = (*)
let infixr 0 `f` ; f = (*)
Prelude> 5 `f` 3 + 4
19
Prelude> :info `f`
f :: Integer -> Integer -> Integer
  	-- Defined at <interactive>:1:19

[simonpj]

Good point. Based on a quick look at the code, it looks as if we simply ignore fixities in let-bound definitions in GHCi.

Fixing this would not be too hard; it's just a question of adding a FixityEnv to InteractiveContext and plumbing it around. Volunteers?

Let's also see if anyone else cares. (An alternative would be simply to warn that the fixity is ignored.)

Simon

[Jedai]

Note that this doesn't only concern backtick functions, but also operators. This is surprising but not really vital (one can always use parenthesis) so maybe a simple warning would be sufficient at least at first.

[pcapriotti]

Added patch.

[simonmar]

Patch looks ok to me.

[p.capriotti@…]

commit 215c8265e72a7f2a8d57793d5a5dec4c0deed08a

Author: Paolo Capriotti <p.capriotti@gmail.com>
Date:   Wed May 2 19:22:10 2012 +0100

    Add a fixity environment to InteractiveContext (#2947)

 compiler/main/HscMain.hs          |    8 ++++----
 compiler/main/HscTypes.lhs        |    4 ++++
 compiler/main/InteractiveEval.hs  |   17 ++++++++++++++---
 compiler/typecheck/TcRnDriver.lhs |   29 +++++++++++++++++------------
 4 files changed, 39 insertions(+), 19 deletions(-)