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QL code and tests for C#/C++/JavaScript.

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Pavel Avgustinov
2018-08-02 17:53:23 +01:00
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javascript/ql/src/Expressions/SelfAssignment.qhelp Normal file
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<!DOCTYPE qhelp PUBLIC
"-//Semmle//qhelp//EN"
"qhelp.dtd">
<qhelp>
<overview>
<p>
Assigning a variable to itself typically indicates a mistake such as a missing
<code>this</code> qualifier or a misspelled variable name.
</p>
</overview>
<recommendation>
<p>
Carefully inspect the assignment to check for misspellings or missing qualifiers.
</p>
</recommendation>
<example>
<p>
In the example below, the constructor function <code>Rectangle</code> is intended
to initialize properties <code>x</code>, <code>y</code>, <code>width</code>, and
<code>height</code> to the parameters of the same names.
</p>
<sample src="examples/SelfAssignment.js" />
<p>
Note, however, that on line 4 the programmer forgot to qualify the left hand side of
the assignment with <code>this</code>: the code now performs a useless assignment of
the <code>width</code> parameter to itself and leaves the <code>width</code>
property uninitialized.
</p>
<p>
To fix this issue, insert a <code>this</code> qualifier:
</p>
<sample src="examples/SelfAssignmentGood.js" />
</example>
<references>
<li>Ecma International, <i>ECMAScript Language Definition</i>, 5.1 Edition, Section 11.13. ECMA, 2011.</li>
</references>
</qhelp>