lichray updated this revision to Diff 411845.
lichray added a comment.
Restore the right diff
Repository:
rG LLVM Github Monorepo
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https://reviews.llvm.org/D120589/new/
https://reviews.llvm.org/D120589
Files:
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Sema/SemaExprCXX.cpp
clang/lib/Sema/SemaType.cpp
clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.type.auto.deduct/p2.cpp
clang/test/CXX/expr/expr.post/expr.type.conv/p1-2b.cpp
clang/test/SemaCXX/deduced-return-type-cxx14.cpp
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
@@ -442,6 +442,15 @@
B() : decltype(auto)() {} // expected-error {{'decltype(auto)' not allowed here}}
};
}
+
+ namespace Cast {
+ void foo() {
+ (void)decltype(auto)(0); // cxx14_20-error{{'decltype(auto)' not allowed here}} \
+ cxx2b-warning{{functional-style cast to 'decltype(auto)' is a Clang extension}}
+ (void)decltype(auto){0}; // cxx14_20-error{{'decltype(auto)' not allowed here}} \
+ cxx2b-warning{{functional-style cast to 'decltype(auto)' is a Clang extension}}
+ }
+ }
}
namespace CurrentInstantiation {
Index: clang/test/CXX/expr/expr.post/expr.type.conv/p1-2b.cpp
===================================================================
--- clang/test/CXX/expr/expr.post/expr.type.conv/p1-2b.cpp
+++ clang/test/CXX/expr/expr.post/expr.type.conv/p1-2b.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -std=c++2b -verify %s
+// RUN: %clang_cc1 -std=c++2b -Wno-decltype-auto-cast -verify %s
template <class T>
void foo(T);
@@ -37,3 +37,26 @@
foo(auto({1, 2})); // expected-error {{cannot deduce actual type for 'auto' from parenthesized initializer list}}
foo(auto{{1, 2}}); // expected-error {{cannot deduce actual type for 'auto' from nested initializer list}}
}
+
+void diagnostics_extension() {
+ foo(decltype(auto)()); // expected-error {{initializer for functional-style cast to 'decltype(auto)' is empty}}
+ foo(decltype(auto){}); // expected-error {{initializer for functional-style cast to 'decltype(auto)' is empty}}
+ foo(decltype(auto)({})); // expected-error {{cannot deduce actual type for 'decltype(auto)' from parenthesized initializer list}}
+ foo(decltype(auto){{}}); // expected-error {{cannot deduce actual type for 'decltype(auto)' from nested initializer list}}
+
+ foo(decltype(auto)({a})); // expected-error {{cannot deduce actual type for 'decltype(auto)' from parenthesized initializer list}}
+ foo(decltype(auto){{a}}); // expected-error {{cannot deduce actual type for 'decltype(auto)' from nested initializer list}}
+
+ foo(decltype(auto)(&A::g)); // expected-error {{reference to overloaded function could not be resolved}}
+
+ foo(decltype(auto)(a, 3.14)); // expected-error {{initializer for functional-style cast to 'decltype(auto)' contains multiple expressions}}
+ foo(decltype(auto){a, 3.14}); // expected-error {{initializer for functional-style cast to 'decltype(auto)' contains multiple expressions}}
+ foo(decltype(auto)({a, 3.14})); // expected-error {{cannot deduce actual type for 'decltype(auto)' from parenthesized initializer list}}
+ foo(decltype(auto){{a, 3.14}}); // expected-error {{cannot deduce actual type for 'decltype(auto)' from nested initializer list}}
+ foo(decltype(auto)({a}, {3.14})); // expected-error {{initializer for functional-style cast to 'decltype(auto)' contains multiple expressions}}
+ foo(decltype(auto){{a}, {3.14}}); // expected-error {{initializer for functional-style cast to 'decltype(auto)' contains multiple expressions}}
+
+ foo(decltype(auto){1, 2}); // expected-error {{initializer for functional-style cast to 'decltype(auto)' contains multiple expressions}}
+ foo(decltype(auto)({1, 2})); // expected-error {{cannot deduce actual type for 'decltype(auto)' from parenthesized initializer list}}
+ foo(decltype(auto){{1, 2}}); // expected-error {{cannot deduce actual type for 'decltype(auto)' from nested initializer list}}
+}
Index: clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.type.auto.deduct/p2.cpp
===================================================================
--- clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.type.auto.deduct/p2.cpp
+++ clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.type.auto.deduct/p2.cpp
@@ -1,6 +1,7 @@
-// RUN: %clang_cc1 -std=c++2b -verify %s
+// RUN: %clang_cc1 -std=c++2b -Wno-decltype-auto-cast -verify %s
// p2.3 allows only T = auto in T(x).
+// As a Clang extension, we also allow T = decltype(auto) to match p2.2 (new T(x)).
void test_decay() {
int v[3];
@@ -9,6 +10,18 @@
static_assert(__is_same(decltype(auto("lit")), char const *));
static_assert(__is_same(decltype(auto{"lit"}), char const *));
+ void(decltype(auto)(v)); // expected-error {{functional-style cast}}
+ void(decltype(auto){v}); // expected-error {{cannot initialize an array element}}
+ static_assert(__is_same(decltype(decltype(auto)("lit")), char const(&)[4]));
+ static_assert(__is_same(decltype(decltype(auto){"lit"}), char const(&)[4]));
+
+ int fn(char *);
+ static_assert(__is_same(decltype(auto(fn)), int (*)(char *)));
+ static_assert(__is_same(decltype(auto{fn}), int (*)(char *)));
+
+ void(decltype(auto)(fn)); // expected-error{{functional-style cast}}
+ void(decltype(auto){fn}); // expected-error{{cannot create object of function type}}
+
constexpr long i = 1;
static_assert(__is_same(decltype(i), long const));
static_assert(__is_same(decltype(auto(1L)), long));
@@ -16,6 +29,12 @@
static_assert(__is_same(decltype(auto(i)), long));
static_assert(__is_same(decltype(auto{i}), long));
+ // scalar prvalue is not cv-qualified
+ static_assert(__is_same(decltype(decltype(auto)(1L)), long));
+ static_assert(__is_same(decltype(decltype(auto){1L}), long));
+ static_assert(__is_same(decltype(decltype(auto)(i)), long));
+ static_assert(__is_same(decltype(decltype(auto){i}), long));
+
class A {
} a;
A const ac;
@@ -23,6 +42,18 @@
static_assert(__is_same(decltype(auto(a)), A));
static_assert(__is_same(decltype(auto(ac)), A));
+ static_assert(__is_same(decltype(decltype(auto)(a)), A));
+ static_assert(__is_same(decltype(decltype(auto)(ac)), A const));
+
+ static_assert(__is_same(decltype(decltype(auto)((a))), A &));
+ static_assert(__is_same(decltype(decltype(auto)((ac))), A const &));
+
+ static_assert(__is_same(decltype(decltype(auto){a}), A));
+ static_assert(__is_same(decltype(decltype(auto){ac}), A const));
+
+ static_assert(__is_same(decltype(decltype(auto){(a)}), A &));
+ static_assert(__is_same(decltype(decltype(auto){(ac)}), A const &));
+
A &lr = a;
A const &lrc = a;
A &&rr = static_cast<A &&>(a);
@@ -32,6 +63,11 @@
static_assert(__is_same(decltype(auto(lrc)), A));
static_assert(__is_same(decltype(auto(rr)), A));
static_assert(__is_same(decltype(auto(rrc)), A));
+
+ static_assert(__is_same(decltype(decltype(auto)(lr)), A &));
+ static_assert(__is_same(decltype(decltype(auto)(lrc)), A const &));
+ static_assert(__is_same(decltype(decltype(auto)(rr)), A &&));
+ static_assert(__is_same(decltype(decltype(auto)(rrc)), A const &&));
}
class cmdline_parser {
@@ -79,3 +115,71 @@
constexpr Uncopyable(Uncopyable &&) = delete;
} u = auto(Uncopyable(auto(Uncopyable(42))));
} // namespace auto_x
+
+// decltype(auto) is no-op to prvalues
+namespace decltype_auto_x {
+constexpr struct Uncopyable {
+ constexpr explicit Uncopyable(int) {}
+ constexpr Uncopyable(Uncopyable &&) = delete;
+} u = decltype(auto)(Uncopyable(decltype(auto)(Uncopyable(42))));
+} // namespace decltype_auto_x
+
+// Forward with decltype(auto)
+constexpr auto invoke1 = [](auto &&x, auto &&y) {
+ return decltype(auto)(x)(decltype(auto)(y));
+};
+
+struct MoveOnly {
+ MoveOnly() = default;
+ MoveOnly(MoveOnly &&) = default;
+ MoveOnly(MoveOnly const &) = delete;
+};
+
+constexpr MoveOnly getMoveOnly() { return {}; }
+
+struct Fn {
+ constexpr int operator()(MoveOnly &) & { return 0; }
+ constexpr int operator()(MoveOnly &&) & { return 1; }
+
+ constexpr int operator()(MoveOnly &) && { return 2; }
+ constexpr int operator()(MoveOnly &&) && { return 3; }
+
+ constexpr int operator()(MoveOnly &) const & { return 4; }
+ constexpr int operator()(MoveOnly &&) const & { return 5; }
+
+ constexpr int operator()(MoveOnly &) const && { return 6; }
+ constexpr int operator()(MoveOnly &&) const && { return 7; }
+};
+
+constexpr void FwdWithDecltypeAuto() {
+ MoveOnly lv;
+ Fn f;
+ constexpr Fn cf;
+
+ static_assert(invoke1(f, lv) == 0);
+ static_assert(invoke1(f, getMoveOnly()) == 1);
+
+ static_assert(invoke1(Fn{}, lv) == 2);
+ static_assert(invoke1(Fn{}, getMoveOnly()) == 3);
+
+ static_assert(invoke1(cf, lv) == 4);
+ static_assert(invoke1(cf, getMoveOnly()) == 5);
+
+ static_assert(invoke1((Fn const){}, lv) == 6);
+ static_assert(invoke1((Fn const){}, getMoveOnly()) == 7);
+}
+
+struct FnArray {
+ template <class T, int N>
+ constexpr int operator()(T (&)[N]) const { return 0; }
+
+ template <class T, int N>
+ constexpr int operator()(T (&&)[N]) const { return 1; }
+};
+
+constexpr void FwdArrayWithDecltypeAuto() {
+ FnArray f;
+
+ static_assert(invoke1(f, "foo") == 0);
+ static_assert(invoke1(f, (int[]){1, 2, 3}) == 1);
+}
Index: clang/lib/Sema/SemaType.cpp
===================================================================
--- clang/lib/Sema/SemaType.cpp
+++ clang/lib/Sema/SemaType.cpp
@@ -3509,9 +3509,8 @@
case DeclaratorContext::FunctionalCast:
if (isa<DeducedTemplateSpecializationType>(Deduced))
break;
- if (SemaRef.getLangOpts().CPlusPlus2b && IsCXXAutoType &&
- !Auto->isDecltypeAuto())
- break; // auto(x)
+ if (SemaRef.getLangOpts().CPlusPlus2b && IsCXXAutoType)
+ break; // auto(x) and decltype(auto)(x)
LLVM_FALLTHROUGH;
case DeclaratorContext::TypeName:
Error = 15; // Generic
Index: clang/lib/Sema/SemaExprCXX.cpp
===================================================================
--- clang/lib/Sema/SemaExprCXX.cpp
+++ clang/lib/Sema/SemaExprCXX.cpp
@@ -1495,8 +1495,11 @@
<< Ty << FullRange);
}
if (getLangOpts().CPlusPlus2b) {
- if (Ty->getAs<AutoType>())
- Diag(TyBeginLoc, diag::warn_cxx20_compat_auto_expr) << FullRange;
+ if (auto *TyAuto = Ty->getAs<AutoType>())
+ Diag(TyBeginLoc, TyAuto->isDecltypeAuto()
+ ? diag::ext_decltype_auto_expr
+ : diag::warn_cxx20_compat_auto_expr)
+ << FullRange;
}
Expr *Deduce = Inits[0];
if (isa<InitListExpr>(Deduce))
@@ -1512,6 +1515,14 @@
return ExprError();
Ty = DeducedType;
+ if (Ty->isReferenceType()) {
+ // decltype(auto)(x) takes a shortcut; see also P0849R2.
+ // FIXME: Substitute auto here to prevent a crash when diagnosing lifetime
+ // of array argument in constant evaluation. Shouldn't be done this way.
+ return BuildCXXFunctionalCastExpr(SubstAutoTypeSourceInfo(TInfo, Ty), Ty,
+ LParenOrBraceLoc, Deduce,
+ RParenOrBraceLoc);
+ }
Entity = InitializedEntity::InitializeTemporary(TInfo, Ty);
}
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2387,6 +2387,9 @@
"cannot form %select{pointer to|reference to|array of}0 'decltype(auto)'">;
def err_decltype_auto_initializer_list : Error<
"cannot deduce 'decltype(auto)' from initializer list">;
+def ext_decltype_auto_expr : ExtWarn<
+ "functional-style cast to 'decltype(auto)' is a Clang extension">,
+ InGroup<DiagGroup<"decltype-auto-cast">>;
// C++17 deduced class template specialization types
def err_deduced_class_template_compound_type : Error<
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