Quuxplusone created this revision.
Quuxplusone added reviewers: sammccall, rsmith, dblaikie, majnemer, mizvekov,
ChuanqiXu.
Quuxplusone added a project: clang.
Quuxplusone requested review of this revision.
Herald added a subscriber: cfe-commits.
Emit the note when we fail to deduce a return type, or deduce conflicting
return types.
It's emitted a //little// too eagerly, e.g. I wish we could avoid it in cases
like
$ bin/clang++ x.cpp
x.cpp:1:19: error: use of undeclared identifier 'x'
auto f() { return x; }
^
x.cpp:1:1: note: deducing return type for 'f'
auto f() { return x; }
^~~~
1 error generated.
But Clang doesn't seem to be able to distinguish "parsing and type-checking the
return //expression//" from "deducing the function's actual return //type//,"
and I'm not inclined to dig this rabbit hole deeper than I already have. I
think this is still a reasonably clean place to stop digging.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D119778
Files:
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Sema/SemaStmt.cpp
clang/test/Sema/invalid-bitwidth-expr.mm
clang/test/SemaCXX/cxx20-p0388-unbound-ary.cpp
clang/test/SemaCXX/cxx2b-consteval-if.cpp
clang/test/SemaCXX/deduced-return-type-cxx14.cpp
clang/test/SemaCXX/deduced-return-void.cpp
clang/test/SemaCXX/std-compare-cxx2a.cpp
clang/test/SemaCXX/typo-correction-crash.cpp
clang/test/SemaOpenCLCXX/template-astype.cl
clang/test/SemaTemplate/concepts.cpp
Index: clang/test/SemaTemplate/concepts.cpp
===================================================================
--- clang/test/SemaTemplate/concepts.cpp
+++ clang/test/SemaTemplate/concepts.cpp
@@ -114,6 +114,7 @@
}
template<typename ...T> void g5() {
([]() -> C<T> auto{ // expected-error-re {{deduced type {{.*}} does not satisfy}}
+ // expected-note@-1 {{deducing return type for 'operator()'}}
return T();
}(), ...);
}
@@ -174,11 +175,17 @@
template<class T> concept C = false; // expected-note 6 {{because 'false' evaluated to false}}
C auto f1() { return void(); } // expected-error {{deduced type 'void' does not satisfy 'C'}}
+ // expected-note@-1 {{deducing return type for 'f1'}}
C auto f2() { return; } // expected-error {{deduced type 'void' does not satisfy 'C'}}
+ // expected-note@-1 {{deducing return type for 'f2'}}
C auto f3() {} // expected-error {{deduced type 'void' does not satisfy 'C'}}
+ // expected-note@-1 {{deducing return type for 'f3'}}
C decltype(auto) f4() { return void(); } // expected-error {{deduced type 'void' does not satisfy 'C'}}
+ // expected-note@-1 {{deducing return type for 'f4'}}
C decltype(auto) f5() { return; } // expected-error {{deduced type 'void' does not satisfy 'C'}}
+ // expected-note@-1 {{deducing return type for 'f5'}}
C decltype(auto) f6() {} // expected-error {{deduced type 'void' does not satisfy 'C'}}
+ // expected-note@-1 {{deducing return type for 'f6'}}
void g() {
f1();
Index: clang/test/SemaOpenCLCXX/template-astype.cl
===================================================================
--- clang/test/SemaOpenCLCXX/template-astype.cl
+++ clang/test/SemaOpenCLCXX/template-astype.cl
@@ -11,6 +11,7 @@
auto neg_test_int(int x) { return templated_astype(x); }
// expected-note@-1{{in instantiation of function template specialization 'templated_astype<int>' requested here}}
+// expected-note@-2{{deducing return type for 'neg_test_int'}}
auto test_short4(short4 x) { return templated_astype(x); }
Index: clang/test/SemaCXX/typo-correction-crash.cpp
===================================================================
--- clang/test/SemaCXX/typo-correction-crash.cpp
+++ clang/test/SemaCXX/typo-correction-crash.cpp
@@ -2,6 +2,7 @@
auto check1() {
return 1;
return s; // expected-error {{use of undeclared identifier 's'}}
+ // expected-note@-3 {{deducing return type for 'check1'}}
}
int test = 11; // expected-note 2 {{'test' declared here}}
@@ -9,6 +10,7 @@
return "s";
return tes; // expected-error {{use of undeclared identifier 'tes'; did you mean 'test'?}}
// expected-error@-1 {{deduced as 'int' here but deduced as 'const char *' in earlier}}
+ // expected-note@-4 {{deducing return type for 'check2'}}
}
template <class A, class B> struct is_same { static constexpr bool value = false; };
Index: clang/test/SemaCXX/std-compare-cxx2a.cpp
===================================================================
--- clang/test/SemaCXX/std-compare-cxx2a.cpp
+++ clang/test/SemaCXX/std-compare-cxx2a.cpp
@@ -32,6 +32,7 @@
auto compare_incomplete_test() {
// expected-error@+1 {{incomplete type 'std::partial_ordering' where a complete type is required}}
return (-1.2 <=> 123.0);
+ // expected-note@-3 {{deducing return type for 'compare_incomplete_test'}}
}
namespace std {
@@ -45,6 +46,7 @@
auto missing_member_test() {
// expected-error@+1 {{standard library implementation of 'std::partial_ordering' is not supported; member 'equivalent' is missing}}
return (1.0 <=> 1.0);
+ // expected-note@-3 {{deducing return type for 'missing_member_test'}}
}
namespace std {
@@ -59,6 +61,7 @@
auto test_non_constexpr_var() {
// expected-error@+1 {{standard library implementation of 'std::strong_ordering' is not supported; member 'equal' does not have expected form}}
return (1 <=> 0);
+ // expected-note@-3 {{deducing return type for 'test_non_constexpr_var'}}
}
#else
@@ -77,6 +80,7 @@
auto test_non_trivial(int LHS, int RHS) {
// expected-error@+1 {{standard library implementation of 'std::strong_ordering' is not supported; the type is not trivially copyable}}
return LHS <=> RHS;
+ // expected-note@-3 {{deducing return type for 'test_non_trivial'}}
}
#endif
Index: clang/test/SemaCXX/deduced-return-void.cpp
===================================================================
--- clang/test/SemaCXX/deduced-return-void.cpp
+++ clang/test/SemaCXX/deduced-return-void.cpp
@@ -16,10 +16,12 @@
auto f4() {
return i;
return; // expected-error {{'auto' in return type deduced as 'void' here but deduced as 'int' in earlier return statement}}
+ // expected-note@-3 {{deducing return type for 'f4'}}
}
auto f5() {
return i;
return void(); // expected-error {{'auto' in return type deduced as 'void' here but deduced as 'int' in earlier return statement}}
+ // expected-note@-3 {{deducing return type for 'f5'}}
}
auto l1 = []() { };
@@ -44,10 +46,12 @@
decltype(auto) f4() {
return i;
return; // expected-error {{'decltype(auto)' in return type deduced as 'void' here but deduced as 'int' in earlier return statement}}
+ // expected-note@-3 {{deducing return type for 'f4'}}
}
decltype(auto) f5() {
return i;
return void(); // expected-error {{'decltype(auto)' in return type deduced as 'void' here but deduced as 'int' in earlier return statement}}
+ // expected-note@-3 {{deducing return type for 'f5'}}
}
auto l1 = []() -> decltype(auto) { };
@@ -56,10 +60,12 @@
auto l4 = []() -> decltype(auto) {
return i;
return; // expected-error {{'decltype(auto)' in return type deduced as 'void' here but deduced as 'int' in earlier return statement}}
+ // expected-note@-3 {{deducing return type for 'operator()'}}
};
auto l5 = []() -> decltype(auto) {
return i;
return void(); // expected-error {{'decltype(auto)' in return type deduced as 'void' here but deduced as 'int' in earlier return statement}}
+ // expected-note@-3 {{deducing return type for 'operator()'}}
};
} // namespace DecltypeAuto
@@ -69,33 +75,41 @@
auto *f1() { } // expected-error {{cannot deduce return type 'auto *' for function with no return statements}}
auto *f2() {
return; // expected-error {{cannot deduce return type 'auto *' from omitted return expression}}
+ // expected-note@-2 {{deducing return type for 'f2'}}
}
auto *f3() {
return void(); // expected-error {{cannot deduce return type 'auto *' from returned value of type 'void'}}
+ // expected-note@-2 {{deducing return type for 'f3'}}
}
auto *f4() {
return &i;
return; // expected-error {{cannot deduce return type 'auto *' from omitted return expression}}
+ // expected-note@-3 {{deducing return type for 'f4'}}
}
auto *f5() {
return &i;
return void(); // expected-error {{cannot deduce return type 'auto *' from returned value of type 'void'}}
+ // expected-note@-3 {{deducing return type for 'f5'}}
}
auto l1 = []() -> auto* { }; // expected-error {{cannot deduce return type 'auto *' for function with no return statements}}
auto l2 = []() -> auto* {
return; // expected-error {{cannot deduce return type 'auto *' from omitted return expression}}
+ // expected-note@-2 {{deducing return type for 'operator()'}}
};
auto l3 = []() -> auto* {
return void(); // expected-error {{cannot deduce return type 'auto *' from returned value of type 'void'}}
+ // expected-note@-2 {{deducing return type for 'operator()'}}
};
auto l4 = []() -> auto* {
return &i;
return; // expected-error {{cannot deduce return type 'auto *' from omitted return expression}}
+ // expected-note@-3 {{deducing return type for 'operator()'}}
};
auto l5 = []() -> auto* {
return &i;
return void(); // expected-error {{cannot deduce return type 'auto *' from returned value of type 'void'}}
+ // expected-note@-3 {{deducing return type for 'operator()'}}
};
} // namespace AutoPtr
@@ -105,32 +119,39 @@
}
auto& f2() {
return; // expected-error {{cannot deduce return type 'auto &' from omitted return expression}}
+ // expected-note@-2 {{deducing return type for 'f2'}}
}
auto& f3() {
return void(); // expected-error@-1 {{cannot form a reference to 'void'}}
+ // expected-note@-2 {{deducing return type for 'f3'}}
}
auto& f4() {
return i;
return; // expected-error {{cannot deduce return type 'auto &' from omitted return expression}}
+ // expected-note@-3 {{deducing return type for 'f4'}}
}
auto& f5() {
return i;
return void(); // expected-error@-2 {{cannot form a reference to 'void'}}
+ // expected-note@-3 {{deducing return type for 'f5'}}
}
auto& f6() { return 42; } // expected-error {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
auto l1 = []() -> auto& { }; // expected-error {{cannot deduce return type 'auto &' for function with no return statements}}
auto l2 = []() -> auto& {
return; // expected-error {{cannot deduce return type 'auto &' from omitted return expression}}
+ // expected-note@-2 {{deducing return type for 'operator()'}}
};
auto l3 = []() -> auto& { // expected-error {{cannot form a reference to 'void'}}
+ // expected-note@-1 {{deducing return type for 'operator()'}}
return void();
};
-auto l4 = []() -> auto& {
+auto l4 = []() -> auto& { // expected-note {{deducing return type for 'operator()'}}
return i;
return; // expected-error {{cannot deduce return type 'auto &' from omitted return expression}}
};
auto l5 = []() -> auto& { // expected-error {{cannot form a reference to 'void'}}
+ // expected-note@-1 {{deducing return type for 'operator()'}}
return i;
return void();
};
Index: clang/test/SemaCXX/deduced-return-type-cxx14.cpp
===================================================================
--- clang/test/SemaCXX/deduced-return-type-cxx14.cpp
+++ clang/test/SemaCXX/deduced-return-type-cxx14.cpp
@@ -82,6 +82,7 @@
auto *ptr_1() {
return 100; // expected-error {{cannot deduce return type 'auto *' from returned value of type 'int'}}
+ // expected-note@-2 {{deducing return type for 'ptr_1'}}
}
const auto &ref_1() {
@@ -106,6 +107,7 @@
auto fac_2(int n) { // expected-note {{declared here}}
if (n > 2)
return n * fac_2(n-1); // expected-error {{cannot be used before it is defined}}
+ // expected-note@-3 {{deducing return type for 'fac_2'}}
return n;
}
@@ -122,6 +124,7 @@
if (false)
return;
return 0; // expected-error {{'auto' in return type deduced as 'int' here but deduced as 'void' in earlier return statement}}
+ // expected-note@-6 {{deducing return type for 'void_ret_4'}}
}
namespace Templates {
Index: clang/test/SemaCXX/cxx2b-consteval-if.cpp
===================================================================
--- clang/test/SemaCXX/cxx2b-consteval-if.cpp
+++ clang/test/SemaCXX/cxx2b-consteval-if.cpp
@@ -4,11 +4,13 @@
constexpr auto f() {
if consteval { return 0; }
if !consteval { return 0.0; } // expected-error {{'auto' in return type deduced as 'double' here but deduced as 'int' in earlier return statement}}
+ // expected-note@-3 {{deducing return type for 'f'}}
}
constexpr auto g() {
if !consteval { return 0; }
if consteval { return 0.0; } // expected-error {{'auto' in return type deduced as 'double' here but deduced as 'int' in earlier return statement}}
+ // expected-note@-3 {{deducing return type for 'g'}}
}
constexpr auto h() {
@@ -19,11 +21,12 @@
constexpr auto i() {
if consteval {
if consteval { // expected-warning {{consteval if is always true in an immediate context}}
- return 1;
- }
- return 2;
+ return 1;
+ }
+ return 2;
} else {
return 1.0; // expected-error {{'auto' in return type deduced as 'double' here but deduced as 'int' in earlier return statement}}
+ // expected-note@-8 {{deducing return type for 'i'}}
}
}
Index: clang/test/SemaCXX/cxx20-p0388-unbound-ary.cpp
===================================================================
--- clang/test/SemaCXX/cxx20-p0388-unbound-ary.cpp
+++ clang/test/SemaCXX/cxx20-p0388-unbound-ary.cpp
@@ -11,6 +11,7 @@
int(&r1)[] = ga;
#if __cplusplus < 202002
// expected-error@-2{{cannot bind to a value of unrelated type}}
+ // expected-note@-4{{deducing return type for 'frob1'}}
#endif
return r1;
@@ -20,6 +21,7 @@
int(&r2)[] = arp;
#if __cplusplus < 202002
// expected-error@-2{{cannot bind to a value of unrelated type}}
+ // expected-note@-4{{deducing return type for 'frob2'}}
#endif
return r2;
Index: clang/test/Sema/invalid-bitwidth-expr.mm
===================================================================
--- clang/test/Sema/invalid-bitwidth-expr.mm
+++ clang/test/Sema/invalid-bitwidth-expr.mm
@@ -13,6 +13,7 @@
auto func() {
return undef(); // expected-error {{use of undeclared identifier}}
+ // expected-note@-2 {{deducing return type for 'func'}}
}
struct Y {
int X : func();
@@ -23,7 +24,7 @@
template <typename T>
struct Base {};
template <typename T>
-auto func() {
+auto func() { // expected-note {{deducing return type for 'func<int>'}}
// error-bit should be propagated from TemplateArgument to NestNameSpecifier.
class Base<decltype(Foo(T()))>::type C; // expected-error {{no matching function for call to 'Foo'}}
return C;
Index: clang/lib/Sema/SemaStmt.cpp
===================================================================
--- clang/lib/Sema/SemaStmt.cpp
+++ clang/lib/Sema/SemaStmt.cpp
@@ -3801,8 +3801,12 @@
Diag(RetExpr->getExprLoc(), diag::err_auto_fn_deduction_failure)
<< OrigResultType.getType() << RetExpr->getType();
- if (DAR != DAR_Succeeded)
+ if (DAR != DAR_Succeeded) {
+ if (OrigResultType.getBeginLoc().isValid())
+ Diag(OrigResultType.getBeginLoc(), diag::note_deducing_return_type_for)
+ << FD << OrigResultType.getSourceRange();
return true;
+ }
// If a local type is part of the returned type, mark its fields as
// referenced.
@@ -3815,6 +3819,9 @@
if (!FD->getReturnType()->getAs<AutoType>()) {
Diag(ReturnLoc, diag::err_auto_fn_return_void_but_not_auto)
<< OrigResultType.getType();
+ if (OrigResultType.getBeginLoc().isValid())
+ Diag(OrigResultType.getBeginLoc(), diag::note_deducing_return_type_for)
+ << FD << OrigResultType.getSourceRange();
return true;
}
// In the case of a return with no operand, the initializer is considered
@@ -3828,8 +3835,12 @@
Diag(ReturnLoc, diag::err_auto_fn_deduction_failure)
<< OrigResultType.getType() << Dummy->getType();
- if (DAR != DAR_Succeeded)
+ if (DAR != DAR_Succeeded) {
+ if (OrigResultType.getBeginLoc().isValid())
+ Diag(OrigResultType.getBeginLoc(), diag::note_deducing_return_type_for)
+ << FD << OrigResultType.getSourceRange();
return true;
+ }
}
// CUDA: Kernel function must have 'void' return type.
@@ -3866,6 +3877,9 @@
Diag(ReturnLoc, diag::err_auto_fn_different_deductions)
<< (AT->isDecltypeAuto() ? 1 : 0)
<< NewAT->getDeducedType() << DeducedT;
+ if (OrigResultType.getBeginLoc().isValid())
+ Diag(OrigResultType.getBeginLoc(), diag::note_deducing_return_type_for)
+ << FD << OrigResultType.getSourceRange();
}
return true;
}
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2466,6 +2466,8 @@
def warn_cxx11_compat_deduced_return_type : Warning<
"return type deduction is incompatible with C++ standards before C++14">,
InGroup<CXXPre14Compat>, DefaultIgnore;
+def note_deducing_return_type_for : Note<
+ "deducing return type for %0">;
// C++11 override control
def override_keyword_only_allowed_on_virtual_member_functions : Error<
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