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<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>1996</year><year>2016</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>erl_lint</title>
    <prepared>Robert Virding</prepared>
    <responsible>Bjarne Dacker</responsible>
    <docno>1</docno>
    <approved>Bjarne D&auml;cker</approved>
    <checked></checked>
    <date>1997-01-27</date>
    <rev>B</rev>
    <file>erl_lint.xml</file>
  </header>
  <module>erl_lint</module>
  <modulesummary>The Erlang code linter.</modulesummary>
  <description>
    <p>This module is used to check Erlang code for illegal syntax and
      other bugs. It also warns against coding practices that are
      not recommended.</p>

    <p>The errors detected include:</p>

    <list type="bulleted">
      <item>Redefined and undefined functions</item>
      <item>Unbound and unsafe variables</item>
      <item>Illegal record use</item>
    </list>

    <p>The warnings detected include:</p>

    <list type="bulleted">
      <item>Unused functions and imports</item>
      <item>Unused variables</item>
      <item>Variables imported into matches</item>
      <item>Variables exported from
        <c>if</c>/<c>case</c>/<c>receive</c></item>
      <item>Variables shadowed in funs and list comprehensions</item>
    </list>

    <p>Some of the warnings are optional, and can be turned on by
      specifying the appropriate option, described below.</p>

    <p>The functions in this module are invoked automatically by the
      Erlang compiler. There is no reason to invoke these
      functions separately unless you have written your own Erlang
      compiler.</p>
  </description>

  <datatypes>
    <datatype>
      <name name="error_info"/>
    </datatype>
    <datatype>
      <name name="error_description"/>
    </datatype>
  </datatypes>

  <funcs>
    <func>
      <name name="format_error" arity="1"/>
      <fsummary>Format an error descriptor.</fsummary>
      <desc>
        <p>Takes an <c><anno>ErrorDescriptor</anno></c> and returns a string
          that describes the error or warning. This function is usually
          called implicitly when processing an <c>ErrorInfo</c> structure
          (see section
          <seealso marker="#errorinfo">Error Information</seealso>).</p>
      </desc>
    </func>

    <func>
      <name name="is_guard_test" arity="1"/>
      <fsummary>Test for a guard test.</fsummary>
      <desc>
        <p>Tests if <c><anno>Expr</anno></c> is a legal guard test.
          <c><anno>Expr</anno></c> is an Erlang term representing the abstract
          form for the expression. <seealso marker="erl_parse#parse_exprs/1">
          <c>erl_parse:parse_exprs(Tokens)</c></seealso>
          can be used to generate a list of <c><anno>Expr</anno></c>.</p>
      </desc>
    </func>

    <func>
      <name name="module" arity="1"/>
      <name name="module" arity="2"/>
      <name name="module" arity="3"/>
      <fsummary>Check a module for errors.</fsummary>
      <desc>
        <p>Checks all the forms in a module for errors. It returns:</p>
        <taglist>
          <tag><c>{ok,<anno>Warnings</anno>}</c></tag>
          <item>
            <p>There are no errors in the module.</p>
          </item>
          <tag><c>{error,<anno>Errors</anno>,<anno>Warnings</anno>}</c></tag>
          <item>
            <p>There are errors in the module.</p>
          </item>
        </taglist>
        <p>As this module is of interest only to the maintainers of the
          compiler, and to avoid the same description in two places, the
          elements of <c>Options</c> that control the warnings are
          only described in the
          <seealso marker="compiler:compile#erl_lint_options">
          <c>compile(3)</c></seealso> module.</p>
        <p><c><anno>AbsForms</anno></c> of a module, which comes from a file
          that is read through <c>epp</c>, the Erlang preprocessor, can come
          from many files. This means that any references to errors must
          include the filename, see the <seealso marker="epp">
          <c>epp(3)</c></seealso> module or parser (see the
          <seealso marker="erl_parse"><c>erl_parse(3)</c></seealso> module).
          The returned errors and warnings have the following format:</p>
        <code type="none">
[{<anno>FileName2</anno>,[<anno>ErrorInfo</anno>]}]</code>
        <p>The errors and warnings are listed in the order in which they are
          encountered in the forms. The errors from one file can therefore be
          split into different entries in the list of errors.</p>
      </desc>
    </func>
  </funcs>

  <section>
    <marker id="errorinfo"/>
    <title>Error Information</title>
    <p><c>ErrorInfo</c> is the standard <c>ErrorInfo</c> structure that is
      returned from all I/O modules. The format is as follows:</p>
    <code type="none">
{ErrorLine, Module, ErrorDescriptor}</code>
    <p>A string describing the error is obtained with the following call:</p>
    <code type="none">
Module:format_error(ErrorDescriptor)</code>
  </section>

  <section>
    <title>See Also</title>
    <p><seealso marker="epp"><c>epp(3)</c></seealso>,
      <seealso marker="erl_parse"><c>erl_parse(3)</c></seealso></p>
  </section>
</erlref>