diagnostic: "module not found" is reported for missing semicolon after import module statement

[zowers]

clang++-19.1 gives incorrect diagnostic when import module statement is not followed by semicolon:
e.g.

import mod1
//         ^ note no semicolon

errors with:

/opt/compiler-explorer/clang-19.1.0/bin/clang++ --gcc-toolchain=/opt/compiler-explorer/gcc-14.2.0   -fcolor-diagnostics -fno-crash-diagnostics -g -std=gnu++20 -Wno-private-header -MD -MT CMakeFiles/test_mod.dir/main.cpp.o -MF CMakeFiles/test_mod.dir/main.cpp.o.d @CMakeFiles/test_mod.dir/main.cpp.o.modmap -o CMakeFiles/test_mod.dir/main.cpp.o -c /app/main.cpp
main.cpp:1:8: fatal error: module 'mod1' not found
    1 | import mod1
      | ~~~~~~~^~~~

while gcc correctly reports

main.cpp:1:12: error: expected ';' before end of line
    1 | import mod1
      |            ^
      |            ;

reproduce link: https://godbolt.org/z/6x3KW6Gx9
main.cpp:

import mod1
//         ^ note no semicolon
int main() {
    return f();
}

mod1.cppm

export module mod1;
export int f()
{
    return 1;
}

CMakeCache.txt

cmake_minimum_required(VERSION 3.28)
project(test_mod)
set(CMAKE_CXX_STANDARD 20)
add_executable(test_mod)
target_sources(test_mod
  PUBLIC
    main.cpp
)
target_sources(test_mod
  PUBLIC
    FILE_SET CXX_MODULES
    FILES
        mod1.cppm
)

[llvmbot]

@llvm/issue-subscribers-clang-modules

Author: Alexander Petrov (zowers)

clang++-19.1 gives incorrect diagnostic when import module statement is not followed by semicolon: e.g. ``` import mod1 // ^ note no semicolon ``` errors with: ``` /opt/compiler-explorer/clang-19.1.0/bin/clang++ --gcc-toolchain=/opt/compiler-explorer/gcc-14.2.0 -fcolor-diagnostics -fno-crash-diagnostics -g -std=gnu++20 -Wno-private-header -MD -MT CMakeFiles/test_mod.dir/main.cpp.o -MF CMakeFiles/test_mod.dir/main.cpp.o.d @CMakeFiles/test_mod.dir/main.cpp.o.modmap -o CMakeFiles/test_mod.dir/main.cpp.o -c /app/main.cpp main.cpp:1:8: fatal error: module 'mod1' not found 1 | import mod1 | ~~~~~~~^~~~ ``` while gcc correctly reports ``` main.cpp:1:12: error: expected ';' before end of line 1 | import mod1 | ^ | ; ``` reproduce link: https://godbolt.org/z/6x3KW6Gx9 main.cpp: ``` import mod1 // ^ note no semicolon int main() { return f(); } ``` mod1.cppm ``` export module mod1; export int f() { return 1; } ``` CMakeCache.txt ``` cmake_minimum_required(VERSION 3.28) project(test_mod) set(CMAKE_CXX_STANDARD 20) add_executable(test_mod) target_sources(test_mod PUBLIC main.cpp ) target_sources(test_mod PUBLIC FILE_SET CXX_MODULES FILES mod1.cppm )

</details>