esl/parse_trans — pull request #6 by nox (2012-04-23 20:31:44+00:00)
Title: Let error markers through parse_transform:do/5

Error markers (`{error, Term}` tuples) in `Forms` are special-cased by `do/5` and make it return a error tuple itself instead of just letting them through. I don't think it is good behaviour as the compiler and its friends already handle error markers correctly. Furthermore it makes `parse_trans_codegen:parse_transform/2` fails when passing the error tuple to `parse_trans:revert/1`.

erlc output before:
```
src/henshin_module.erl:none: error in parse transform 'parse_trans_codegen': {function_clause,
[{lists,flatten,
[error],
[{file,"lists.erl"},
{line,550}]},
{parse_trans,revert,1,
[{file,
"src/parse_trans.erl"},
{line,515}]},
{compile,
'-foldl_transform/2-anonymous-2-',
2,
[{file,"compile.erl"},
{line,843}]},
{compile,foldl_transform,2,
[{file,"compile.erl"},
{line,845}]},
{compile,
'-internal_comp/4-anonymous-1-',
2,
[{file,"compile.erl"},
{line,269}]},
{compile,fold_comp,3,
[{file,"compile.erl"},
{line,287}]},
{compile,internal_comp,4,
[{file,"compile.erl"},
{line,271}]},
{compile,internal,3,
[{file,"compile.erl"},
{line,246}]}]}
```

erlc output after:
```
src/henshin_module.erl:189: syntax error before: '<-'
src/henshin_module.erl:59: Warning: variable 'TransformedRules' is unused
src/henshin_module.erl:60: Warning: variable 'HenshinMods' is unused
src/henshin_module.erl:60: Warning: variable 'OptsErrors' is unused
```