Fix FP unusedStructMember

[mptre]

Triggering while a function parameter has the same name as a struct member.

[chrchr-github]

Either there are typos in the test case (s -> S), or I don't understand the FP.
As it stands, I would expect a warning for the given code.

[mptre]

Either there are typos in the test case (`s` -> `S`), or I don't understand the FP. As it stands, I would expect a warning for the given code.

Typo in test, fixed.

[chrchr-github]

With your change applied, will we still warn about S::a?

struct S { int a; };
struct T f(int a) {
    struct T t = {.a = 1};
    return t;
}

[mptre]

With your change applied, will we still warn about `S::a`? ~~~c struct S { int a; }; struct T f(int a) { struct T t = {.a = 1}; return t; } ~~~

Correct

[mptre]

With your change applied, will we still warn about `S::a`? ~~~c struct S { int a; }; struct T f(int a) { struct T t = {.a = 1}; return t; } ~~~

My bad, must have tried this out on the wrong branch before. It does not warn about S::a in the provided example anymore. Makes one wonder if the a field in the initializer should really be flagged as a variable?

[chrchr-github]

The root cause is likely the wrong varid:

1: struct S { int a@var1 ; } ;
2: struct T f ( int a@var2 ) {
3: struct T t@var3 ; t@var3 = { .@exprUNIQUE a@var2 = 1 } ;
4: return t@var3 ;
5: }

[chrchr-github]

There is this similar ticket: https://trac.cppcheck.net/ticket/13123