Cannot use fields in requires expression before declaration

[AlexeyDmitriev]

Bugzilla Link	50290
Resolution	DUPLICATE
Resolved on	Oct 18, 2021 08:39
Version	trunk
OS	All
CC	@AaronBallman,@zygoloid

Extended Description

If I use field (or this->field) inside the requires requires, clang supposes it not existent.

Code:

struct S {
double result() {
return 0;
}
};
template
class Outer {
public:
double result() requires requires {this->inner.result();} {
return inner.result();
}
Inner inner;
};
double foo() {
Outer c;
return c.result();
}

Compiler explorer link: https://godbolt.org/z/zdcTjYoE8

If I change this to

class Outer {
public:
double result() requires requires {this->inner.result();} {
return inner.result();
}
Inner inner;
};

, then it does work.

I expect original code to work because normally inside a class all variables are considered (e.g return inner.result(); is fine), but maybe I am not correct and there is wording that prohibits this code.

Note that gcc does compile this code (which I understand doesn't mean the code is correct)

options I've used: -std=c++20

clang++ -v gives me

#​1 with x86-64 clang (trunk)
clang version 13.0.0 (https://github.com/llvm/llvm-project.git 0f8854f)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/compiler-explorer/clang-trunk/bin
Found candidate GCC installation: /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0
Selected GCC installation: /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@MX32
Selected multilib: .;@m64
(in-process)
"/opt/compiler-explorer/clang-trunk-20210510/bin/clang-13" -cc1 -triple x86_64-unknown-linux-gnu -S -disable-free -disable-llvm-verifier -discard-value-names -main-file-name example.cpp -mrelocation-model static -mframe-pointer=all -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning -debug-info-kind=limited -dwarf-version=4 -debugger-tuning=gdb -v -fcoverage-compilation-dir=/app -resource-dir /opt/compiler-explorer/clang-trunk-20210510/lib/clang/13.0.0 -isystem /opt/compiler-explorer/libs/outcome/single-header -internal-isystem /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0 -internal-isystem /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/x86_64-linux-gnu -internal-isystem /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/backward -internal-isystem /opt/compiler-explorer/clang-trunk-20210510/lib/clang/13.0.0/include -internal-isystem /usr/local/include -internal-isystem /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -std=c++20 -fdeprecated-macro -fdebug-compilation-dir=/app -ferror-limit 19 -fgnuc-version=4.2.1 -fno-implicit-modules -fcxx-exceptions -fexceptions -fcolor-diagnostics -mllvm --x86-asm-syntax=intel -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /app/output.s -x c++
clang -cc1 version 13.0.0 based upon LLVM 13.0.0git default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../x86_64-linux-gnu/include"
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
/opt/compiler-explorer/libs/outcome/single-header
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/x86_64-linux-gnu
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/backward
/opt/compiler-explorer/clang-trunk-20210510/lib/clang/13.0.0/include
/usr/local/include
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.

[AaronBallman]

*** This bug has been marked as a duplicate of bug #44178 ***