test: Add passDouble smoke test #294

Mostly for clang-tidy to cover commit 733c64318d1c75acee8cea74abaf88050453c089

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Tested locally with the nix CI config:

[5/7] Building CXX object test/CMakeFiles/mptest.dir/mp/test/foo.capnp.proxy-client.c++.o
FAILED: [code=1] test/CMakeFiles/mptest.dir/mp/test/foo.capnp.proxy-client.c++.o
/nix/store/r9941n32g4wyvggz2703dlplbdq8a6rd-cmake-4.1.2/bin/cmake -E __run_co_compile --tidy="/nix/store/wcwr4iq7c8f4ygn8bd1q0k3i51lmhz35-clang-21.1.8/bin/clang-tidy;--extra-arg-before=--driver-mode=g++" --source=/tmp/tmp.A7Li
qAWKn2/git_dir/build-llvm/test/mp/test/foo.capnp.proxy-client.c++ -- /nix/store/fhwhpg79dwbmb7wg18864l8rk9j8634g-clang-wrapper-21.1.8/bin/clang++ -DKJ_USE_FIBERS -I/tmp/tmp.A7LiqAWKn2/git_dir/build-llvm/test -I/tmp/tmp.A7LiqAW
Kn2/git_dir/include -I/tmp/tmp.A7LiqAWKn2/git_dir/test -I/tmp/tmp.A7LiqAWKn2/git_dir/build-llvm/include -isystem /nix/store/njqpk50gg9b2awwdl4g8hdg048j7x7y8-libcxx-21.1.8-dev/include -isystem /nix/store/0balwgpf53vhjycd97mq1bkmz45nc1ks-compiler-rt-libc-21.1.8-dev/include -isystem /nix/store/i2vcdjg0hvr52qfh0il5jrfrg3c4h53m-capnproto-1.4.0/include -isystem /nix/store/wxws7pwyzk8mbmjc1rwwwx9v184hh67v-openssl-3.6.2-dev/include -isystem /nix/store/h7ik0g1xxayy0z8h27zbvrgmac63irgs-zlib-1.3.2-dev/include -isystem /nix/store/njqpk50gg9b2awwdl4g8hdg048j7x7y8-libcxx-21.1.8-dev/include/c++/v1 -isystem /nix/store/fhwhpg79dwbmb7wg18864l8rk9j8634g-clang-wrapper-21.1.8/resource-root/include -isystem /nix/store/15h9askp4k1lx44d9871wid23j2a8ijp-glibc-2.42-61-dev/include -Werror -Wall -Wextra -Wpedantic -Wthread-safety -Wno-unused-parameter -std=gnu++20 -pthread -MD -MT test/CMakeFiles/mptest.dir/mp/test/foo.capnp.proxy-client.c++.o -MF test/CMakeFiles/mptest.dir/mp/test/foo.capnp.proxy-client.c++.o.d -o test/CMakeFiles/mptest.dir/mp/test/foo.capnp.proxy-client.c++.o -c /tmp/tmp.A7LiqAWKn2/git_dir/build-llvm/test/mp/test/foo.capnp.proxy-client.c++
/tmp/tmp.A7LiqAWKn2/git_dir/include/mp/type-number.h:85:87: error: use nullptr [modernize-use-nullptr,-warnings-as-errors]
   85 |     typename std::enable_if<std::is_floating_point<LocalType>::value>::type* enable = 0)
      |                                                                                       ^
      |                                                                                       nullptr
179 warnings generated.
Suppressed 177 warnings (177 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
1 warning treated as error

ci failure can be ignored :melting_face:

Also, unrelated, I noticed that the CI not reproducible. Locally the iwyu CI fails with:

<details><summary>iwyu err</summary>

CI_CONFIG=ci/configs/llvm.bash ci/scripts/run.sh 
+ '[' x ']'
+ source ci/configs/llvm.bash
++ CI_DESC='CI job using LLVM-based libraries and tools (clang, libc++, clang-tidy, iwyu) and testing Ninja'
++ CI_DIR=build-llvm
++ NIX_ARGS=(--arg enableLibcxx true)
++ export CXX=clang++
++ CXX=clang++
++ export 'CXXFLAGS=-Werror -Wall -Wextra -Wpedantic -Wthread-safety -Wno-unused-parameter'
++ CXXFLAGS='-Werror -Wall -Wextra -Wpedantic -Wthread-safety -Wno-unused-parameter'
++ CMAKE_ARGS=(-G Ninja -DMP_ENABLE_CLANG_TIDY=ON -DMP_ENABLE_IWYU=ON)
++ BUILD_ARGS=(-k 0)
+ nix develop --ignore-environment --keep CI_CONFIG --keep CI_CLEAN --arg enableLibcxx true -f shell.nix --command ci/scripts/ci.sh
+ '[' x ']'
+ source ci/configs/llvm.bash
++ CI_DESC='CI job using LLVM-based libraries and tools (clang, libc++, clang-tidy, iwyu) and testing Ninja'
++ CI_DIR=build-llvm
++ NIX_ARGS=(--arg enableLibcxx true)
++ export CXX=clang++
++ CXX=clang++
++ export 'CXXFLAGS=-Werror -Wall -Wextra -Wpedantic -Wthread-safety -Wno-unused-parameter'
++ CXXFLAGS='-Werror -Wall -Wextra -Wpedantic -Wthread-safety -Wno-unused-parameter'
++ CMAKE_ARGS=(-G Ninja -DMP_ENABLE_CLANG_TIDY=ON -DMP_ENABLE_IWYU=ON)
++ BUILD_ARGS=(-k 0)
+ : build-llvm
+ '[' -v BUILD_TARGETS ']'
+ BUILD_TARGETS=(all tests mpexamples)
+ '[' -n '' ']'
+ cmake --version
cmake version 4.1.2

CMake suite maintained and supported by Kitware (kitware.com/cmake).
++ cmake --version
++ awk '/version/{print $3; exit}'
+ cmake_ver=4.1.2
+ src_dir=/tmp/tmp.CdXP7X55gV/git_dir
+ mkdir -p build-llvm
+ cd build-llvm
+ cmake /tmp/tmp.CdXP7X55gV/git_dir -G Ninja -DMP_ENABLE_CLANG_TIDY=ON -DMP_ENABLE_IWYU=ON
-- The CXX compiler identification is Clang 21.1.8
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /nix/store/fhwhpg79dwbmb7wg18864l8rk9j8634g-clang-wrapper-21.1.8/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Success
-- Found Threads: TRUE
-- Performing Test HAVE_PTHREAD_GETNAME_NP
-- Performing Test HAVE_PTHREAD_GETNAME_NP - Success
-- Performing Test HAVE_PTHREAD_THREADID_NP
-- Performing Test HAVE_PTHREAD_THREADID_NP - Failed
-- Performing Test HAVE_PTHREAD_GETTHREADID_NP
-- Performing Test HAVE_PTHREAD_GETTHREADID_NP - Failed
-- Configuring done (3.8s)
-- Generating done (0.1s)
-- Build files have been written to: /tmp/tmp.CdXP7X55gV/git_dir/build-llvm
+ ver_ge 4.1.2 3.15
++ printf '%s\n' 3.15 4.1.2
++ sort -V
++ head -n1
+ '[' 3.15 = 3.15 ']'
+ cmake --build . -t all tests mpexamples -- -k 0
[1/60] Compiling Cap'n Proto schema include/mp/proxy.capnp
[2/60] Building CXX object CMakeFiles/multiprocess.dir/include/mp/proxy.capnp.c++.o
[3/60] Building CXX object CMakeFiles/mpgen.dir/src/mp/gen.cpp.o
FAILED: [code=1] CMakeFiles/mpgen.dir/src/mp/gen.cpp.o 
/nix/store/r9941n32g4wyvggz2703dlplbdq8a6rd-cmake-4.1.2/bin/cmake -E __run_co_compile --iwyu="/nix/store/zkvvr6wn4x6c2wjj9pfi5k896gsm337m-include-what-you-use-0.26/bin/include-what-you-use;-Xiwyu;--error;-Xiwyu;--mapping_file=/nix/store/njqpk50gg9b2awwdl4g8hdg048j7x7y8-libcxx-21.1.8-dev/include/c++/v1/libcxx.imp;--driver-mode=g++" --tidy="/nix/store/wcwr4iq7c8f4ygn8bd1q0k3i51lmhz35-clang-21.1.8/bin/clang-tidy;--extra-arg-before=--driver-mode=g++" --source=/tmp/tmp.CdXP7X55gV/git_dir/src/mp/gen.cpp -- /nix/store/fhwhpg79dwbmb7wg18864l8rk9j8634g-clang-wrapper-21.1.8/bin/clang++ -DKJ_USE_FIBERS -I/tmp/tmp.CdXP7X55gV/git_dir/build-llvm/include -I/tmp/tmp.CdXP7X55gV/git_dir/include -isystem /nix/store/njqpk50gg9b2awwdl4g8hdg048j7x7y8-libcxx-21.1.8-dev/include -isystem /nix/store/0balwgpf53vhjycd97mq1bkmz45nc1ks-compiler-rt-libc-21.1.8-dev/include -isystem /nix/store/i2vcdjg0hvr52qfh0il5jrfrg3c4h53m-capnproto-1.4.0/include -isystem /nix/store/wxws7pwyzk8mbmjc1rwwwx9v184hh67v-openssl-3.6.2-dev/include -isystem /nix/store/h7ik0g1xxayy0z8h27zbvrgmac63irgs-zlib-1.3.2-dev/include -isystem /nix/store/njqpk50gg9b2awwdl4g8hdg048j7x7y8-libcxx-21.1.8-dev/include/c++/v1 -isystem /nix/store/fhwhpg79dwbmb7wg18864l8rk9j8634g-clang-wrapper-21.1.8/resource-root/include -isystem /nix/store/15h9askp4k1lx44d9871wid23j2a8ijp-glibc-2.42-61-dev/include -Werror -Wall -Wextra -Wpedantic -Wthread-safety -Wno-unused-parameter -std=gnu++20 -pthread -MD -MT CMakeFiles/mpgen.dir/src/mp/gen.cpp.o -MF CMakeFiles/mpgen.dir/src/mp/gen.cpp.o.d -o CMakeFiles/mpgen.dir/src/mp/gen.cpp.o -c /tmp/tmp.CdXP7X55gV/git_dir/src/mp/gen.cpp
Warning: include-what-you-use reported diagnostics:

/tmp/tmp.CdXP7X55gV/git_dir/src/mp/gen.cpp should add these lines:
#include <capnp/schema.capnp.h>   // for Annotation

/tmp/tmp.CdXP7X55gV/git_dir/src/mp/gen.cpp should remove these lines:

The full include-list for /tmp/tmp.CdXP7X55gV/git_dir/src/mp/gen.cpp:
#include <capnp/schema-parser.h>  // for ParsedSchema, SchemaParser
#include <capnp/schema.capnp.h>   // for Annotation
#include <capnp/schema.h>         // for Type, InterfaceSchema, StructSchema
#include <kj/array.h>             // for Array, heapArray
#include <kj/common.h>            // for mv, KJ_IF_MAYBE, NullableValue, Arr...
#include <kj/filesystem.h>        // for ReadableDirectory, Directory, Files...
#include <kj/memory.h>            // for Own, OwnOwn
#include <kj/string.h>            // for StringPtr
#include <mp/config.h>            // for capnp_PREFIX, CMAKE_INSTALL_PREFIX
#include <mp/util.h>              // for ExecProcess, WaitProcess
#include <unistd.h>               // for fork
#include <algorithm>              // for __transform, transform
#include <cerrno>                 // for errno
#include <cstdint>                // for uint64_t, int32_t
#include <cstdio>                 // for size_t
#include <cstdlib>                // for exit
#include <fstream>                // for basic_ofstream, basic_ostream, oper...
#include <functional>             // for function
#include <initializer_list>       // for initializer_list
#include <iostream>               // for cerr
#include <map>                    // for map, operator!=, __map_iterator
#include <set>                    // for set
#include <sstream>                // for basic_ostringstream
#include <stdexcept>              // for runtime_error
#include <string>                 // for basic_string, char_traits, allocator
#include <system_error>           // for system_error, system_category
#include <utility>                // for pair, declval
#include <vector>                 // for vector
---

[4/60] Building CXX object CMakeFiles/mputil.dir/src/mp/util.cpp.o
[5/60] Building CXX object CMakeFiles/multiprocess.dir/src/mp/proxy.cpp.o
[6/60] Linking CXX static library libmultiprocess.a
ninja: build stopped: cannot make progress due to previous errors.

</details>

Maybe it could make sense to bump the GHA nix channel to be more recent?

Code review ACK faaedb11f8a75b26941820aac7dbdabe164a4647. Thanks for the test!

re: #294 (comment)

ci failure can be ignored 🫠

Yep, CI failure is fixed by #286 (just needs review)

re: #294 (comment)

Also, unrelated, I noticed that the CI not reproducible. Locally the iwyu CI fails with:

I think the IWYU error is also fixed by #286 since I ran IWYU locally, and the cause is that a different capnproto version is used. It probably make sense to update the nixpkgs channel too as you suggest.