Hi Richard,
Thanks for the reply. The problem has something to do with how LH
currently handles symbols. Internally, LH uses the idScope field to
identify whether a symbol is exported and handles them differently (e.g.
erase the unique id only when the symbol is exported). Ideally, we want
LH to be aware of the case where an exported Id is labeled as local but
it's probably easier to let GHC set the idScope as if we were accessing
from a different module.
We tried using tidyExpr to turn the LocalIds into GlobalIds
(https://github.com/jprider63/ghc-elaboration-test/blob/49b33d42bdefb597ac8fab49bb4cea4969c929b3/src/Test/Plugin.hs#L101)
but the output expression still shows lid for QQQ. Are there any flags
we need to set to "trick" GHC into setting those ids as globals?
Thanks,
-Yiyun
On 8/31/21 3:25 PM, Richard Eisenberg wrote:
I took a look at this today. I found
Note [GlobalId/LocalId]
~~~~~~~~~~~~~~~~~~~~~~~
A GlobalId is
* always a constant (top-level)
* imported, or data constructor, or primop, or record selector
* has a Unique that is globally unique across the whole
GHC invocation (a single invocation may compile multiple modules)
* never treated as a candidate by the free-variable finder;
it's a constant!
A LocalId is
* bound within an expression (lambda, case, local let(rec))
* or defined at top level in the module being compiled
* always treated as a candidate by the free-variable finder
After CoreTidy, top-level LocalIds are turned into GlobalIds
This suggests that the output you're seeing -- with "lid" in QQQ and "gid" in
PPP -- is correct. What has drawn your attention to this problem? Is there something else that's
misbehaving?
Thanks,
Richard
On Aug 25, 2021, at 4:16 PM, Yiyun Liu <liuyi...@terpmail.umd.edu> wrote:
Hi all,
We have a function in Liquidhaskell's code base for converting
refinement expressions into GHC's core expressions using the GHC API.
Its implementation is based on tcRnExpr
<https://gitlab.haskell.org/ghc/ghc/-/blob/ghc-8.10.6-release/compiler/typecheck/TcRnDriver.hs#L2358>except
we keep the typechecked expression and desugar it before returning.
However, our function fails to set the idScope information properly when
LiquidHaskell is invoked as a plugin (installed as a
typeCheckResultAction). This repo
<https://github.com/yiyunliu/ghc-elaboration-test>contains a minimal
example that demonstrates the issue. In the CoreExpr returned by
elabRnExpr
<https://github.com/yiyunliu/ghc-elaboration-test/blob/cb7397884b7949e6b7fb6617ded10e86ee5dcad2/src/Test/Plugin.hs#L71>,
every symbol from the current module that's being compiled is labeled as
local. The README.md file shows how the exported symbol testPlus is
marked as local in QQQ.hs, the module where it's defined.
Is there a function we should call to set the idScope information properly?
Thanks,
-Yiyun
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