https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122417
Bug ID: 122417
Summary: Improve diagnostic for shadowing typedef with a
declaration that uses type inference
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: luigighiron at gmail dot com
Target Milestone: ---
Here are two programs which incorrectly shadow a typedef with a declaration
that uses type inference, and their error messages generated by GCC (<source>
is the name of the file on godbolt).
Program 1:
typedef int A;
int main(){
auto A=0;
}
Error 1:
<source>:3:11: error: expected identifier or '(' before '=' token
3 | auto A=0;
| ^
Program 2:
typedef int B;
int main(){
auto(B)=0;
}
Error 2:
<source>:3:10: error: expected identifier or '(' before 'B'
3 | auto(B)=0;
| ^
The message in error 1 is correct, but it would be helpful to point out
specifically here that this cannot declare A. Also a pointer operator * or
attribute specifier sequence [[...]] could validly occur after A (e.g. auto
A[[]]x=0;), so it's not even comprehensive either. The message in error 2 is
outright confusing, B is an identifier and the token before B is an opening
parenthesis. I think it is worth improving the error messages in both programs
to specifically mention that a typedef being visible with the same name
prevents type inference from being used.
