The problem is round-tripping cases like this, which are valid
( /// ) :: Int -> Int -> Int
a /// b = 3
baz :: Int -> Int -> Int
a ` baz ` b = 4
There can be arbitrary spaces between the surrounding parens and the
operator name, and between the backquotes and the identifier in the infix
version.
In each case we simply get a RdrName, which in turn is wrapped in HsVar or
whatever.
The D538 productions are of the form
var :: { Located RdrName }
: varid { $1 }
| '(' varsym ')' {% ams (sLL $1 $> (unLoc $2))
[mo $1,mj AnnVal $2,mc $3] }
and
tyvarop :: { Located RdrName }
tyvarop : '`' tyvarid '`' {% ams (sLL $1 $> (unLoc $2))
[mj AnnBackquote $1,mj AnnVal $2
,mj AnnBackquote $3] }
So the location tracks the entire span, but we need annotations for the
three individual parts.
Note: I did not check how far close to the limit the performance was prior
to this change, it may have been the last 1% to take it over.
Alan
On Fri, Dec 12, 2014 at 11:03 PM, Simon Peyton Jones
I am now adding an `AnnVal` to every RdrName, to be able to separate it out from any decoration, such as surrounding backticks or parens.
That seems like overkill to me. (a `op` b) is an HsOpApp, and must of course have backticks unless op is an operator like (a + b), in which case it doesn’t.
The corner case is something like ((`op`) a b), which will parse as (HsApp (HsApp (HsVar op) (HsVar a)) (HsVar b)). But it would be silly for us to get bent out of shape because of such a vanishingly rare corner case. Instead, if you really want to reflect it faithfully, add a new constructor for “parens around backticks”).
Let’s only take these overheads when there is real reason to do so.
Simon
*From:* ghc-devs [mailto:ghc-devs-bounces@haskell.org] *On Behalf Of *Alan & Kim Zimmerman *Sent:* 12 December 2014 14:22 *To:* ghc-devs@haskell.org *Subject:* D538 and compiler performance spec
For API annotations I am working in the details of RdrNames, which come in a bewildering variety of syntactic forms.
My latest change causes perf/compiler to fail, with
bytes allocated value is too high: Expected parsing001(normal) bytes allocated: 587079016 +/-5% Lower bound parsing001(normal) bytes allocated: 557725065 Upper bound parsing001(normal) bytes allocated: 616432967 Actual parsing001(normal) bytes allocated: 704940512 Deviation parsing001(normal) bytes allocated: 20.1 %
I am now adding an `AnnVal` to every RdrName, to be able to separate it out from any decoration, such as surrounding backticks or parens.
Is this a problem? The alternative would be to add a SourceText field to RdrName.
Alan