Happy parser file compilation causes panic

Sorry I can't be more descriptive, but I'm not exactly sure what's causing the compile time crash. I can compile it on GHC 7.4.1, but it crashes for GHC 7.6.3.

╭─ting@noa ~/panic  ‹python-2.7.3›  ‹master›
╰─➤  ghc DeclareParse.hs
[1 of 4] Compiling Base             ( Base.hs, Base.o )
[2 of 4] Compiling Lexer            ( Lexer.hs, Lexer.o )
[3 of 4] Compiling Declare          ( Declare.hs, Declare.o )
[4 of 4] Compiling DeclareParse     ( DeclareParse.hs, DeclareParse.o )
ghc: panic! (the 'impossible' happened)
(GHC version 7.6.3 for x86_64-unknown-linux):
    Prelude.head: empty list

    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

I've uploaded all the files here to check out: https://gist.github.com/wting/a6787a3f50ee41dda611

Trac metadata

Trac field	Value
Version	7.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 5

added Tbug Trac import labels

Attached file Base.hs ($950).

Attached file Declare.hs ($951).

Attached file DeclareParse.hs ($952).

Attached file DeclareTest.hs ($953).

Attached file Lexer.hs ($954).

Attached file README.md (download).

Sorry, this also fails on 7.4.1:

╭─ting@sloth ~/code/cs345  ‹python-2.7.3›  ‹hw2› 
╰─➤  ghc DeclareParse.hs
[1 of 4] Compiling Base             ( Base.hs, Base.o )
[2 of 4] Compiling Lexer            ( Lexer.hs, Lexer.o )
[3 of 4] Compiling Declare          ( Declare.hs, Declare.o )
[4 of 4] Compiling DeclareParse     ( DeclareParse.hs, DeclareParse.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.4.1 for x86_64-unknown-linux):
	Prelude.head: empty list

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

I'm going to try and investigate further.

closed

This seems to be fixed in 7.8:

23:18:03 ~/temp/bug> ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.8.20140130
23:18:06 ~/temp/bug> ghc DeclareParse.hs
[1 of 4] Compiling Base             ( Base.hs, Base.o )
[2 of 4] Compiling Lexer            ( Lexer.hs, Lexer.o )
[3 of 4] Compiling Declare          ( Declare.hs, Declare.o )
[4 of 4] Compiling DeclareParse     ( DeclareParse.hs, DeclareParse.o )

DeclareParse.hs:177:11: Not in scope: data constructor ‛Subtract’

DeclareParse.hs:193:11: Not in scope: data constructor ‛Multiply’

DeclareParse.hs:202:11: Not in scope: data constructor ‛Divide’

For the record, I was able to reproduce the bug with 7.6.3.

Thanks for reporting!

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedDuplicate

For the record: it's bug #7882 (closed).

added compiler crash label

added Pnormal label