fix #25870 #25846: var return type in C++ backend - #26008
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genProcParams strips tfVarIsPtr from the proc signature so C++ procs with var T return produce T& instead of T*. However the call sites that assign results to T* temporaries (the else branches of fixupCall, genClosureCall, and genNamedParamCall) were not updated to match - they stored the T& result directly into a T* variable, causing a dangling pointer (SIGSEGV) or a clang compilation error on macOS. This broke std/oserrors.nim in C++ mode when msg[^1] appeared inside an and expression, triggering the splitDecls > 0 code path. Fix: wrap the call result with cAddr() when tfVarIsPtr is set on the return type, matching what getTempCpp already does.
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genNamedParamCall only runs for sfNamedParamCall procs, which come from importObjC and compile to ObjC (.nim.m). ObjC has no C++ references, so var T is a pointer there and the cAddr() I added would produce T**. The compileToCpp branch above it is also dead since importObjC modules don't go through the C++ backend. Pointed out by demotomohiro.
…ath forces T* signature)
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fix #25870 #25846: C++ codegen for proc returning var T
The C++ codegen was generating conflicting types for procs with �ar T return:
the signature said T& but the internal result variable was T*, and callers
expected T& back. This caused link errors on some platforms (undefined symbols)
and clang errors on macOS.
The problem was that fVarIsPtr was being set too early (in semexprs) and leaked
into the proc type, so every place that looked at the return type saw T* instead
of T&. The fix moves the flag application into cgen where it belongs: we make a
shallow copy of the return type, set fVarIsPtr on the copy, and keep the
original clean for the signature.
There were also a few call sites that weren't updated when the signature changed
from T* to T&. Stuff like s[^1] in an �nd expression would hit the
splitDecls path and try to store a T& into a T* variable, which clang rightfully
refuses to compile. These now get the missing & operator.
Tested with
im c and
im cpp on the new test case, plus --threads:on.