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<H1>erl_lint</H1>
</CENTER>

<H3>MODULE</H3>
<DIV CLASS=REFBODY>
erl_lint
</DIV>

<H3>MODULE SUMMARY</H3>
<DIV CLASS=REFBODY>
The Erlang Code Linter
</DIV>

<H3>DESCRIPTION</H3>
<DIV CLASS=REFBODY>

<P>This module is used to check Erlang code for illegal syntax and
other bugs. It also warns against coding practices which are
not recommended. 
<P>The errors detected include:
<P>
<UL>

<LI>
redefined and undefined functions
</LI>


<LI>
unbound and unsafe variables
</LI>


<LI>
illegal record usage.
</LI>


</UL>

<P>Warnings include:
<P>
<UL>

<LI>
unused functions and imports
</LI>


<LI>
unused variables
</LI>


<LI>
variables imported into matches
</LI>


<LI>
variables exported from
         <CODE>if</CODE>/<CODE>case</CODE>/<CODE>receive</CODE>
</LI>


<LI>
variables shadowed in lambdas and list
comprehensions.
</LI>


</UL>

<P>Some of the warnings are optional, and can be turned on by
giving the appropriate option, described below.
<P>The functions in this module are invoked automatically by the
Erlang compiler and there is no reason to invoke these
functions separately unless you have written your own Erlang
compiler.
</DIV>

<H3>EXPORTS</H3>

<P><A NAME="module/1"><STRONG><CODE>module(AbsForms) -&#62; {ok,Warnings} 
| {error,Errors,Warnings}</CODE></STRONG></A><BR>
<A NAME="module/2"><STRONG><CODE>module(AbsForms, FileName) -&#62; {ok,Warnings} 
| {error,Errors,Warnings}</CODE></STRONG></A><BR>
<A NAME="module/3"><STRONG><CODE>module(AbsForms, FileName, CompileOptions) -&#62; 
{ok,Warnings} | {error,Errors,Warnings}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>AbsForms = [term()]</CODE></STRONG><BR>
<STRONG><CODE>FileName = FileName2 = atom() | string()</CODE></STRONG><BR>
<STRONG><CODE>Warnings = Errors = [{Filename2,[ErrorInfo]}]</CODE></STRONG><BR>
<STRONG><CODE>ErrorInfo = see separate description below.</CODE></STRONG><BR>
<STRONG><CODE>CompileOptions = [term()]</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>This function checks all the forms in a module for errors.
It returns:


<P>
<DL>

<DT>
<CODE>{ok,Warnings}</CODE>
</DT>

<DD>
There were no errors in the module.<BR>

</DD>

<DT>
<CODE>{error,Errors,Warnings}</CODE>
</DT>

<DD>
There were errors in the module.<BR>

</DD>

</DL>

<P>Since this module is of interest only to the maintainers of
         the compiler, and to avoid having the same description in
         two places to avoid the usual maintainence nightmare, the
         elements of <CODE>Options</CODE> that control the warnings are
         only described in <A HREF="javascript:erlhref('../../../../', 'compiler', 'compile.html#erl_lint_options');">compile(3)</A>.


<P>The <CODE>AbsForms</CODE> of a module which comes from a file
that is read through <CODE>epp</CODE>, the Erlang pre-processor,
can come from many files. This means that any references to
errors must include the file name (see <A HREF="epp.html">epp(3)</A>, or parser <A HREF="erl_parse.html">erl_parse(3)</A> The warnings and
errors returned have the following format:


<PRE>
    [{FileName2,[ErrorInfo]}]
</PRE>

<P>The errors and warnings are listed in the order in which
they are encountered in the forms. This means that the
errors from one file may be split into different entries in
the list of errors.

</DIV>

<P><A NAME="is_guard_test/1"><STRONG><CODE>is_guard_test(Expr) -&#62; bool()</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Expr = term()</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>This function tests if <CODE>Expr</CODE> is a legal guard test.
         <CODE>Expr</CODE> is an Erlang term representing the abstract form
         for the expression. <CODE>erl_parse:parse_exprs(Tokens)</CODE> can
         be used to generate a list of <CODE>Expr</CODE>.

</DIV>

<P><A NAME="format_error/1"><STRONG><CODE>format_error(ErrorDescriptor) -&#62; Chars</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>ErrorDescriptor = errordesc()</CODE></STRONG><BR>
<STRONG><CODE>Chars = [char() | Chars]</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Takes an <CODE>ErrorDescriptor</CODE> and returns a string which
describes the error or warning. This function is usually
called implicitly when processing an <CODE>ErrorInfo</CODE>
structure (see below).

</DIV>

<H3>Error Information</H3>
<DIV CLASS=REFBODY>

<P>The <CODE>ErrorInfo</CODE> mentioned above is the standard
<CODE>ErrorInfo</CODE> structure which is returned from all IO
modules. It has the following format:


<PRE>
    {ErrorLine, Module, ErrorDescriptor}
</PRE>

<P>A string which describes the error is obtained with the following call:


<PRE>
apply(Module, format_error, ErrorDescriptor)
</PRE>

</DIV>

<H3>See Also</H3>
<DIV CLASS=REFBODY>

<P><A HREF="erl_parse.html">erl_parse(3)</A>,
<A HREF="epp.html">epp(3)</A>

</DIV>

<H3>AUTHORS</H3>
<DIV CLASS=REFBODY>
Robert Virding - support@erlang.ericsson.se<BR>

</DIV>
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