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Add UFCS failure case error diagnostics #1023

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merged 2 commits into from
Mar 16, 2024
+137 −117
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Add UFCS failure case error diagnostics #1023

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2297606
Add UFCS failure case error diagnostics
hsutter Mar 16, 2024
cf3ef9a
Restore UFCS SFINAE test to just _NONLOCAL versions
hsutter Mar 16, 2024
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54 changes: 37 additions & 17 deletions include/cpp2util.h
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Original file line number Diff line number Diff line change
@@ -27,7 +27,7 @@
// 2) Entities in namespace cpp2::impl::, and macros
//
// These should not be used by the program. They form the language
// support library intended to be called only from generated Cpp2 code.
// support library intended to be called only from generated code.
//
// For example, if a Cpp2 function leaves a local variable
// uninitialized, cppfront will generate uses of impl::deferred_init<>
@@ -887,6 +887,7 @@ class out {
#endif
#endif

#define CPP2_UFCS_EMPTY(...)
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Maybe CPP2_UFCS_EMPTY wasn't necessary, and passing CPP2_UFCS_IDENTITY instead would have done the job.

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But then all the cases would be the same again, and we'd have the original problem in non-SFINAE cases?

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Ah, you're right.

#define CPP2_UFCS_IDENTITY(...) __VA_ARGS__
#define CPP2_UFCS_REMPARENS(...) __VA_ARGS__

@@ -937,30 +938,49 @@ class out {
#define CPP2_UFCS_CONSTRAINT_ARG(...) IsViable
#endif

#define CPP2_UFCS_(LAMBDADEFCAPT,MVFWD,QUALID,TEMPKW,...) \
template <class T> struct dependent_false : std::false_type {};

#define CPP2_UFCS_(LAMBDADEFCAPT,SFINAE,MVFWD,QUALID,TEMPKW,...) \
[LAMBDADEFCAPT]< \
typename Obj, typename... Params \
CPP2_UFCS_IS_NOTHROW_PARAM(MVFWD,QUALID,TEMPKW,__VA_ARGS__) \
CPP2_UFCS_CONSTRAINT_PARAM(MVFWD,QUALID,TEMPKW,__VA_ARGS__) \
> \
CPP2_LAMBDA_NO_DISCARD (Obj&& obj, Params&& ...params) CPP2_FORCE_INLINE_LAMBDA_CLANG \
noexcept(CPP2_UFCS_IS_NOTHROW_ARG(MVFWD,QUALID,TEMPKW,__VA_ARGS__)) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) \
requires CPP2_UFCS_CONSTRAINT_ARG(MVFWD,QUALID,TEMPKW,__VA_ARGS__) { \
if constexpr (requires{ CPP2_FORWARD(obj).CPP2_UFCS_REMPARENS QUALID TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); }) { \
return CPP2_FORWARD(obj).CPP2_UFCS_REMPARENS QUALID TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); \
} else { \
return MVFWD(CPP2_UFCS_REMPARENS QUALID __VA_ARGS__)(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
SFINAE( requires CPP2_UFCS_CONSTRAINT_ARG(MVFWD,QUALID,TEMPKW,__VA_ARGS__) ) \
{ \
if constexpr (requires{ CPP2_FORWARD(obj).CPP2_UFCS_REMPARENS QUALID TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); }) { \
return CPP2_FORWARD(obj).CPP2_UFCS_REMPARENS QUALID TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); \
} \
}

#define CPP2_UFCS(...) CPP2_UFCS_(&,CPP2_UFCS_IDENTITY,(),,__VA_ARGS__)
#define CPP2_UFCS_MOVE(...) CPP2_UFCS_(&,std::move,(),,__VA_ARGS__)
#define CPP2_UFCS_FORWARD(...) CPP2_UFCS_(&,CPP2_FORWARD,(),,__VA_ARGS__)
#define CPP2_UFCS_TEMPLATE(...) CPP2_UFCS_(&,CPP2_UFCS_IDENTITY,(),template,__VA_ARGS__)
#define CPP2_UFCS_QUALIFIED_TEMPLATE(QUALID,...) CPP2_UFCS_(&,CPP2_UFCS_IDENTITY,QUALID,template,__VA_ARGS__)
#define CPP2_UFCS_NONLOCAL(...) CPP2_UFCS_(,CPP2_UFCS_IDENTITY,(),,__VA_ARGS__)
#define CPP2_UFCS_TEMPLATE_NONLOCAL(...) CPP2_UFCS_(,CPP2_UFCS_IDENTITY,(),template,__VA_ARGS__)
#define CPP2_UFCS_QUALIFIED_TEMPLATE_NONLOCAL(QUALID,...) CPP2_UFCS_(,CPP2_UFCS_IDENTITY,QUALID,template,__VA_ARGS__)
else if constexpr (requires{ MVFWD(CPP2_UFCS_REMPARENS QUALID __VA_ARGS__)(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); }) { \
return MVFWD(CPP2_UFCS_REMPARENS QUALID __VA_ARGS__)(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
} \
else if constexpr (requires{ obj.CPP2_UFCS_REMPARENS QUALID TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); }) { \
static_assert( cpp2::impl::dependent_false<Obj>::value, "this function call syntax tries 'obj.func(...)', then 'func(obj,...);' - both failed, but the first would have succeeded if obj were an lvalue - the likely problem is that this is a definite last use of the object (which automatically treats it as an rvalue / move candidate), and the function cannot accept an rvalue" ); \
CPP2_FORWARD(obj).CPP2_UFCS_REMPARENS QUALID TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); \
MVFWD(CPP2_UFCS_REMPARENS QUALID __VA_ARGS__)(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
} \
else if constexpr (requires{ MVFWD(CPP2_UFCS_REMPARENS QUALID __VA_ARGS__)(obj, CPP2_FORWARD(params)...); }) { \
static_assert( cpp2::impl::dependent_false<Obj>::value, "this function call syntax tries 'obj.func(...)', then 'func(obj,...);' - both failed, but the second would have succeeded if obj were an lvalue - the likely problem is that this is a definite last use of the object, (which automatically treats it as an rvalue / move candidate) and the function cannot accept an rvalue" ); \
CPP2_FORWARD(obj).CPP2_UFCS_REMPARENS QUALID TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); \
MVFWD(CPP2_UFCS_REMPARENS QUALID __VA_ARGS__)(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
} \
else { \
static_assert( cpp2::impl::dependent_false<Obj>::value, "this function call syntax tries 'obj.func(...)', then 'func(obj,...);' - both failed, did you spell the function name correctly?" ); \
CPP2_FORWARD(obj).CPP2_UFCS_REMPARENS QUALID TEMPKW __VA_ARGS__(CPP2_FORWARD(params)...); \
MVFWD(CPP2_UFCS_REMPARENS QUALID __VA_ARGS__)(CPP2_FORWARD(obj), CPP2_FORWARD(params)...); \
} \
}

#define CPP2_UFCS(...) CPP2_UFCS_(&,CPP2_UFCS_EMPTY,CPP2_UFCS_IDENTITY,(),,__VA_ARGS__)
#define CPP2_UFCS_MOVE(...) CPP2_UFCS_(&,CPP2_UFCS_EMPTY,std::move,(),,__VA_ARGS__)
#define CPP2_UFCS_FORWARD(...) CPP2_UFCS_(&,CPP2_UFCS_EMPTY,CPP2_FORWARD,(),,__VA_ARGS__)
#define CPP2_UFCS_TEMPLATE(...) CPP2_UFCS_(&,CPP2_UFCS_EMPTY,CPP2_UFCS_IDENTITY,(),template,__VA_ARGS__)
#define CPP2_UFCS_QUALIFIED_TEMPLATE(QUALID,...) CPP2_UFCS_(&,CPP2_UFCS_EMPTY,CPP2_UFCS_IDENTITY,QUALID,template,__VA_ARGS__)
#define CPP2_UFCS_NONLOCAL(...) CPP2_UFCS_(,CPP2_UFCS_IDENTITY,CPP2_UFCS_IDENTITY,(),,__VA_ARGS__)
#define CPP2_UFCS_TEMPLATE_NONLOCAL(...) CPP2_UFCS_(,CPP2_UFCS_IDENTITY,CPP2_UFCS_IDENTITY,(),template,__VA_ARGS__)
#define CPP2_UFCS_QUALIFIED_TEMPLATE_NONLOCAL(QUALID,...) CPP2_UFCS_(,CPP2_UFCS_IDENTITY,CPP2_UFCS_IDENTITY,QUALID,template,__VA_ARGS__)

} // impl

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