[clang] [Clang] Added explanation why a is constructible evaluated to false. (PR #143309)
Shamshura Egor via cfe-commits
cfe-commits at lists.llvm.org
Mon Jun 9 09:19:03 PDT 2025
https://github.com/egorshamshura updated https://github.com/llvm/llvm-project/pull/143309
>From ed1f379144736e0c645dca87b0111f685bdd7e53 Mon Sep 17 00:00:00 2001
From: Shamshura Egor <shamshuraegor at gmail.com>
Date: Sun, 8 Jun 2025 13:09:54 +0000
Subject: [PATCH 1/2] Fixed problem when std::is_xxx_v<> tries to get Argument
as type when it is pack; added is_constructible support
---
.../clang/Basic/DiagnosticSemaKinds.td | 7 +-
clang/lib/Sema/SemaTypeTraits.cpp | 35 ++++++++-
.../type-traits-unsatisfied-diags-std.cpp | 72 +++++++++++++++++++
.../SemaCXX/type-traits-unsatisfied-diags.cpp | 44 ++++++++++++
4 files changed, 154 insertions(+), 4 deletions(-)
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 5f44d503580b9..b04537d2cac3c 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1765,7 +1765,8 @@ def err_user_defined_msg_constexpr : Error<
// Type traits explanations
def note_unsatisfied_trait : Note<"%0 is not %enum_select<TraitName>{"
"%TriviallyRelocatable{trivially relocatable}|"
- "%TriviallyCopyable{trivially copyable}"
+ "%TriviallyCopyable{trivially copyable}|"
+ "%Constructible{constructible with provided types}"
"}1">;
def note_unsatisfied_trait_reason
@@ -1785,7 +1786,9 @@ def note_unsatisfied_trait_reason
"%UserProvidedAssign{has a user provided %select{copy|move}1 "
"assignment operator}|"
"%UnionWithUserDeclaredSMF{is a union with a user-declared "
- "%sub{select_special_member_kind}1}"
+ "%sub{select_special_member_kind}1}|"
+ "%FunctionType{is a function type}|"
+ "%CVVoidType{is a cv void type}"
"}0">;
def warn_consteval_if_always_true : Warning<
diff --git a/clang/lib/Sema/SemaTypeTraits.cpp b/clang/lib/Sema/SemaTypeTraits.cpp
index 330f2aa750a09..37fe965815269 100644
--- a/clang/lib/Sema/SemaTypeTraits.cpp
+++ b/clang/lib/Sema/SemaTypeTraits.cpp
@@ -21,6 +21,7 @@
#include "clang/Sema/Overload.h"
#include "clang/Sema/Sema.h"
#include "clang/Sema/SemaHLSL.h"
+#include "llvm/Support/raw_ostream.h"
using namespace clang;
@@ -1941,6 +1942,7 @@ static std::optional<TypeTrait> StdNameToTypeTrait(StringRef Name) {
.Case("is_trivially_relocatable",
TypeTrait::UTT_IsCppTriviallyRelocatable)
.Case("is_trivially_copyable", TypeTrait::UTT_IsTriviallyCopyable)
+ .Case("is_constructible", TypeTrait::TT_IsConstructible)
.Default(std::nullopt);
}
@@ -1977,8 +1979,14 @@ static ExtractedTypeTraitInfo ExtractTypeTraitFromExpression(const Expr *E) {
Trait = StdNameToTypeTrait(Name);
if (!Trait)
return std::nullopt;
- for (const auto &Arg : VD->getTemplateArgs().asArray())
- Args.push_back(Arg.getAsType());
+ for (const auto &Arg : VD->getTemplateArgs().asArray()) {
+ if (Arg.getKind() == TemplateArgument::ArgKind::Pack) {
+ for (const auto &InnerArg : Arg.pack_elements())
+ Args.push_back(InnerArg.getAsType());
+ }
+ if (Arg.getKind() == TemplateArgument::ArgKind::Type)
+ Args.push_back(Arg.getAsType());
+ }
return {{Trait.value(), std::move(Args)}};
}
@@ -2159,6 +2167,26 @@ static void DiagnoseNonTriviallyCopyableReason(Sema &SemaRef,
}
}
+static void DiagnoseNonConstructibleReason(Sema &SemaRef, SourceLocation Loc,
+ QualType T) {
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait)
+ << T << diag::TraitName::Constructible;
+
+ if (T->isFunctionType())
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::FunctionType;
+
+ if (T->isVoidType())
+ SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+ << diag::TraitNotSatisfiedReason::CVVoidType;
+
+ const CXXRecordDecl *D = T->getAsCXXRecordDecl();
+ if (!D || D->isInvalidDecl() || !D->hasDefinition())
+ return;
+
+ SemaRef.Diag(D->getLocation(), diag::note_defined_here) << D;
+}
+
static void DiagnoseNonTriviallyCopyableReason(Sema &SemaRef,
SourceLocation Loc, QualType T) {
SemaRef.Diag(Loc, diag::note_unsatisfied_trait)
@@ -2195,6 +2223,9 @@ void Sema::DiagnoseTypeTraitDetails(const Expr *E) {
case UTT_IsTriviallyCopyable:
DiagnoseNonTriviallyCopyableReason(*this, E->getBeginLoc(), Args[0]);
break;
+ case TT_IsConstructible:
+ DiagnoseNonConstructibleReason(*this, E->getBeginLoc(), Args[0]);
+ break;
default:
break;
}
diff --git a/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp b/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
index 498e202e26265..b9ee677a1cffc 100644
--- a/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
+++ b/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
@@ -20,6 +20,14 @@ struct is_trivially_copyable {
template <typename T>
constexpr bool is_trivially_copyable_v = __is_trivially_copyable(T);
+
+template <typename... Args>
+struct is_constructible {
+ static constexpr bool value = __is_constructible(Args...);
+};
+
+template <typename... Args>
+constexpr bool is_constructible_v = __is_constructible(Args...);
#endif
#ifdef STD2
@@ -44,6 +52,17 @@ using is_trivially_copyable = __details_is_trivially_copyable<T>;
template <typename T>
constexpr bool is_trivially_copyable_v = __is_trivially_copyable(T);
+
+template <typename... Args>
+struct __details_is_constructible{
+ static constexpr bool value = __is_constructible(Args...);
+};
+
+template <typename... Args>
+using is_constructible = __details_is_constructible<Args...>;
+
+template <typename... Args>
+constexpr bool is_constructible_v = __is_constructible(Args...);
#endif
@@ -73,6 +92,15 @@ using is_trivially_copyable = __details_is_trivially_copyable<T>;
template <typename T>
constexpr bool is_trivially_copyable_v = is_trivially_copyable<T>::value;
+
+template <typename... Args>
+struct __details_is_constructible : bool_constant<__is_constructible(Args...)> {};
+
+template <typename... Args>
+using is_constructible = __details_is_constructible<Args...>;
+
+template <typename... Args>
+constexpr bool is_constructible_v = is_constructible<Args...>::value;
#endif
}
@@ -100,6 +128,17 @@ static_assert(std::is_trivially_copyable_v<int&>);
// expected-note at -1 {{because it is a reference type}}
+static_assert(std::is_constructible<int, int>::value);
+
+static_assert(std::is_constructible<void>::value);
+// expected-error-re at -1 {{static assertion failed due to requirement 'std::{{.*}}is_constructible<void>::value'}} \
+// expected-note at -1 {{'void' is not constructible with provided types}} \
+// expected-note at -1 {{because it is a cv void type}}
+static_assert(std::is_constructible_v<void>);
+// expected-error at -1 {{static assertion failed due to requirement 'std::is_constructible_v<void>'}} \
+// expected-note at -1 {{'void' is not constructible with provided types}} \
+// expected-note at -1 {{because it is a cv void type}}
+
namespace test_namespace {
using namespace std;
static_assert(is_trivially_relocatable<int&>::value);
@@ -119,6 +158,15 @@ namespace test_namespace {
// expected-error at -1 {{static assertion failed due to requirement 'is_trivially_copyable_v<int &>'}} \
// expected-note at -1 {{'int &' is not trivially copyable}} \
// expected-note at -1 {{because it is a reference type}}
+
+ static_assert(is_constructible<void>::value);
+ // expected-error-re at -1 {{static assertion failed due to requirement '{{.*}}is_constructible<void>::value'}} \
+ // expected-note at -1 {{'void' is not constructible with provided types}} \
+ // expected-note at -1 {{because it is a cv void type}}
+ static_assert(is_constructible_v<void>);
+ // expected-error at -1 {{static assertion failed due to requirement 'is_constructible_v<void>'}} \
+ // expected-note at -1 {{'void' is not constructible with provided types}} \
+ // expected-note at -1 {{because it is a cv void type}}
}
@@ -139,6 +187,15 @@ concept C2 = std::is_trivially_copyable_v<T>; // #concept4
template <C2 T> void g2(); // #cand4
+template <typename... Args>
+requires std::is_constructible<Args...>::value void f3(); // #cand5
+
+template <typename... Args>
+concept C3 = std::is_constructible_v<Args...>; // #concept6
+
+template <C3 T> void g3(); // #cand6
+
+
void test() {
f<int&>();
// expected-error at -1 {{no matching function for call to 'f'}} \
@@ -169,5 +226,20 @@ void test() {
// expected-note@#concept4 {{because 'std::is_trivially_copyable_v<int &>' evaluated to false}} \
// expected-note@#concept4 {{'int &' is not trivially copyable}} \
// expected-note@#concept4 {{because it is a reference type}}
+
+ f3<void>();
+ // expected-error at -1 {{no matching function for call to 'f3'}} \
+ // expected-note@#cand5 {{candidate template ignored: constraints not satisfied [with Args = <void>]}} \
+ // expected-note-re@#cand5 {{because '{{.*}}is_constructible<void>::value' evaluated to false}} \
+ // expected-note@#cand5 {{'void' is not constructible with provided types}} \
+ // expected-note@#cand5 {{because it is a cv void type}}
+
+ g3<void>();
+ // expected-error at -1 {{no matching function for call to 'g3'}} \
+ // expected-note@#cand6 {{candidate template ignored: constraints not satisfied [with T = void]}} \
+ // expected-note@#cand6 {{because 'void' does not satisfy 'C3'}} \
+ // expected-note@#concept6 {{because 'std::is_constructible_v<void>' evaluated to false}} \
+ // expected-note@#concept6 {{'void' is not constructible with provided types}} \
+ // expected-note@#concept6 {{because it is a cv void type}}
}
}
diff --git a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
index 0256569fcca5f..9e668ef86b31a 100644
--- a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
+++ b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
@@ -290,3 +290,47 @@ static_assert(__is_trivially_copyable(S12));
// expected-note at -1 {{'S12' is not trivially copyable}} \
// expected-note@#tc-S12 {{'S12' defined here}}
}
+
+namespace constructible {
+
+struct S1 { // #c-S1
+ S1(int);
+};
+static_assert(__is_constructible(S1, int, float));
+// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(constructible::S1, int, float)'}} \
+// expected-note at -1 {{'S1' is not constructible with provided types}} \
+// expected-note@#c-S1 {{'S1' defined here}}
+
+struct S2 { // #c-S2
+ S2(int, float, double);
+};
+static_assert(__is_constructible(S2, float));
+// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(constructible::S2, float)'}} \
+// expected-note at -1 {{'S2' is not constructible with provided types}} \
+// expected-note@#c-S2 {{'S2' defined here}}
+
+static_assert(__is_constructible(void));
+// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(void)'}} \
+// expected-note at -1 {{'void' is not constructible with provided types}} \
+// expected-note at -1 {{because it is a cv void type}}
+
+static_assert(__is_constructible(const void));
+// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(const void)'}} \
+// expected-note at -1 {{'const void' is not constructible with provided types}} \
+// expected-note at -1 {{because it is a cv void type}}
+
+static_assert(__is_constructible(volatile void));
+// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(volatile void)'}} \
+// expected-note at -1 {{'volatile void' is not constructible with provided types}} \
+// expected-note at -1 {{because it is a cv void type}}
+
+static_assert(__is_constructible(int ()));
+// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(int ())'}} \
+// expected-note at -1 {{'int ()' is not constructible with provided types}} \
+// expected-note at -1 {{because it is a function type}}
+
+static_assert(__is_constructible(void (int, float)));
+// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(void (int, float))'}} \
+// expected-note at -1 {{'void (int, float)' is not constructible with provided types}} \
+// expected-note at -1 {{because it is a function type}}
+}
>From ef7955642a1f3f2a45ec26277021d8c7ee671e1a Mon Sep 17 00:00:00 2001
From: Shamshura Egor <shamshuraegor at gmail.com>
Date: Mon, 9 Jun 2025 16:18:48 +0000
Subject: [PATCH 2/2] Updated DiagnoseNonTriviallyCopyableReason, changed tests
to current version.
---
clang/lib/Sema/SemaTypeTraits.cpp | 53 ++++++++++++++++---
.../type-traits-unsatisfied-diags-std.cpp | 6 ---
.../SemaCXX/type-traits-unsatisfied-diags.cpp | 11 +---
3 files changed, 48 insertions(+), 22 deletions(-)
diff --git a/clang/lib/Sema/SemaTypeTraits.cpp b/clang/lib/Sema/SemaTypeTraits.cpp
index 37fe965815269..2b2e0c5d05891 100644
--- a/clang/lib/Sema/SemaTypeTraits.cpp
+++ b/clang/lib/Sema/SemaTypeTraits.cpp
@@ -21,7 +21,6 @@
#include "clang/Sema/Overload.h"
#include "clang/Sema/Sema.h"
#include "clang/Sema/SemaHLSL.h"
-#include "llvm/Support/raw_ostream.h"
using namespace clang;
@@ -2167,11 +2166,23 @@ static void DiagnoseNonTriviallyCopyableReason(Sema &SemaRef,
}
}
-static void DiagnoseNonConstructibleReason(Sema &SemaRef, SourceLocation Loc,
- QualType T) {
- SemaRef.Diag(Loc, diag::note_unsatisfied_trait)
- << T << diag::TraitName::Constructible;
+static void DiagnoseNonConstructibleReason(
+ Sema &SemaRef, SourceLocation Loc,
+ const llvm::SmallVector<clang::QualType, 1> &Ts) {
+ bool CompleteTypes = true;
+ for (const auto &ArgTy : Ts) {
+ if (ArgTy->isVoidType() || ArgTy->isIncompleteArrayType())
+ continue;
+ if (ArgTy->isIncompleteType()) {
+ SemaRef.Diag(Loc, diag::err_incomplete_type_used_in_type_trait_expr)
+ << ArgTy;
+ CompleteTypes = false;
+ }
+ }
+ if (!CompleteTypes)
+ return;
+ QualType T = Ts[0];
if (T->isFunctionType())
SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
<< diag::TraitNotSatisfiedReason::FunctionType;
@@ -2183,8 +2194,36 @@ static void DiagnoseNonConstructibleReason(Sema &SemaRef, SourceLocation Loc,
const CXXRecordDecl *D = T->getAsCXXRecordDecl();
if (!D || D->isInvalidDecl() || !D->hasDefinition())
return;
-
SemaRef.Diag(D->getLocation(), diag::note_defined_here) << D;
+
+ llvm::BumpPtrAllocator OpaqueExprAllocator;
+ SmallVector<Expr *, 2> ArgExprs;
+ ArgExprs.reserve(Ts.size() - 1);
+ for (unsigned I = 1, N = Ts.size(); I != N; ++I) {
+ QualType ArgTy = Ts[I];
+ if (ArgTy->isObjectType() || ArgTy->isFunctionType())
+ ArgTy = SemaRef.Context.getRValueReferenceType(ArgTy);
+ ArgExprs.push_back(
+ new (OpaqueExprAllocator.Allocate<OpaqueValueExpr>())
+ OpaqueValueExpr(Loc, ArgTy.getNonLValueExprType(SemaRef.Context),
+ Expr::getValueKindForType(ArgTy)));
+ }
+
+ EnterExpressionEvaluationContext Unevaluated(
+ SemaRef, Sema::ExpressionEvaluationContext::Unevaluated);
+ Sema::SFINAETrap SFINAE(SemaRef, /*ForValidityCheck=*/true);
+ Sema::ContextRAII TUContext(SemaRef,
+ SemaRef.Context.getTranslationUnitDecl());
+ InitializedEntity To(InitializedEntity::InitializeTemporary(T));
+ InitializationKind InitKind(InitializationKind::CreateDirect(Loc, Loc, Loc));
+ InitializationSequence Init(SemaRef, To, InitKind, ArgExprs);
+
+ if (Init.Diagnose(SemaRef, To, InitKind, ArgExprs)) {
+ auto ArgsRange = SourceRange(ArgExprs.front()->getBeginLoc(),
+ ArgExprs.back()->getEndLoc());
+
+ SemaRef.Diag(Loc, diag::err_ovl_no_viable_function_in_init) << T;
+ }
}
static void DiagnoseNonTriviallyCopyableReason(Sema &SemaRef,
@@ -2224,7 +2263,7 @@ void Sema::DiagnoseTypeTraitDetails(const Expr *E) {
DiagnoseNonTriviallyCopyableReason(*this, E->getBeginLoc(), Args[0]);
break;
case TT_IsConstructible:
- DiagnoseNonConstructibleReason(*this, E->getBeginLoc(), Args[0]);
+ DiagnoseNonConstructibleReason(*this, E->getBeginLoc(), Args);
break;
default:
break;
diff --git a/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp b/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
index b9ee677a1cffc..a600c8029b768 100644
--- a/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
+++ b/clang/test/SemaCXX/type-traits-unsatisfied-diags-std.cpp
@@ -132,11 +132,9 @@ static_assert(std::is_constructible<int, int>::value);
static_assert(std::is_constructible<void>::value);
// expected-error-re at -1 {{static assertion failed due to requirement 'std::{{.*}}is_constructible<void>::value'}} \
-// expected-note at -1 {{'void' is not constructible with provided types}} \
// expected-note at -1 {{because it is a cv void type}}
static_assert(std::is_constructible_v<void>);
// expected-error at -1 {{static assertion failed due to requirement 'std::is_constructible_v<void>'}} \
-// expected-note at -1 {{'void' is not constructible with provided types}} \
// expected-note at -1 {{because it is a cv void type}}
namespace test_namespace {
@@ -161,11 +159,9 @@ namespace test_namespace {
static_assert(is_constructible<void>::value);
// expected-error-re at -1 {{static assertion failed due to requirement '{{.*}}is_constructible<void>::value'}} \
- // expected-note at -1 {{'void' is not constructible with provided types}} \
// expected-note at -1 {{because it is a cv void type}}
static_assert(is_constructible_v<void>);
// expected-error at -1 {{static assertion failed due to requirement 'is_constructible_v<void>'}} \
- // expected-note at -1 {{'void' is not constructible with provided types}} \
// expected-note at -1 {{because it is a cv void type}}
}
@@ -231,7 +227,6 @@ void test() {
// expected-error at -1 {{no matching function for call to 'f3'}} \
// expected-note@#cand5 {{candidate template ignored: constraints not satisfied [with Args = <void>]}} \
// expected-note-re@#cand5 {{because '{{.*}}is_constructible<void>::value' evaluated to false}} \
- // expected-note@#cand5 {{'void' is not constructible with provided types}} \
// expected-note@#cand5 {{because it is a cv void type}}
g3<void>();
@@ -239,7 +234,6 @@ void test() {
// expected-note@#cand6 {{candidate template ignored: constraints not satisfied [with T = void]}} \
// expected-note@#cand6 {{because 'void' does not satisfy 'C3'}} \
// expected-note@#concept6 {{because 'std::is_constructible_v<void>' evaluated to false}} \
- // expected-note@#concept6 {{'void' is not constructible with provided types}} \
// expected-note@#concept6 {{because it is a cv void type}}
}
}
diff --git a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
index 9e668ef86b31a..17a9fb61ce80f 100644
--- a/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
+++ b/clang/test/SemaCXX/type-traits-unsatisfied-diags.cpp
@@ -296,9 +296,8 @@ namespace constructible {
struct S1 { // #c-S1
S1(int);
};
-static_assert(__is_constructible(S1, int, float));
-// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(constructible::S1, int, float)'}} \
-// expected-note at -1 {{'S1' is not constructible with provided types}} \
+static_assert(__is_constructible(S1, char*));
+// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(constructible::S1, char *)'}} \
// expected-note@#c-S1 {{'S1' defined here}}
struct S2 { // #c-S2
@@ -306,31 +305,25 @@ struct S2 { // #c-S2
};
static_assert(__is_constructible(S2, float));
// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(constructible::S2, float)'}} \
-// expected-note at -1 {{'S2' is not constructible with provided types}} \
// expected-note@#c-S2 {{'S2' defined here}}
static_assert(__is_constructible(void));
// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(void)'}} \
-// expected-note at -1 {{'void' is not constructible with provided types}} \
// expected-note at -1 {{because it is a cv void type}}
static_assert(__is_constructible(const void));
// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(const void)'}} \
-// expected-note at -1 {{'const void' is not constructible with provided types}} \
// expected-note at -1 {{because it is a cv void type}}
static_assert(__is_constructible(volatile void));
// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(volatile void)'}} \
-// expected-note at -1 {{'volatile void' is not constructible with provided types}} \
// expected-note at -1 {{because it is a cv void type}}
static_assert(__is_constructible(int ()));
// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(int ())'}} \
-// expected-note at -1 {{'int ()' is not constructible with provided types}} \
// expected-note at -1 {{because it is a function type}}
static_assert(__is_constructible(void (int, float)));
// expected-error at -1 {{static assertion failed due to requirement '__is_constructible(void (int, float))'}} \
-// expected-note at -1 {{'void (int, float)' is not constructible with provided types}} \
// expected-note at -1 {{because it is a function type}}
}
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