Assigning a variable to itself typically indicates a mistake such as a missing qualifier or a misspelled variable name.

Carefully inspect the assignment to check for misspellings or missing qualifiers.

In the example below, the struct type Rect has two setter methods setWidth and setHeight that are meant to be used to update the width and height fields, respectively:

Note, however, that in setHeight the programmer forgot to qualify the left-hand side of the assignment with the receiver variable r, so the method performs a useless assignment of the width parameter to itself and leaves the width field unchanged.

To fix this issue, insert a qualifier:

The Go Programming Language Specification: Assignments.