[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-04-05 Thread Mariya Podchishchaeva via cfe-commits 

https://github.com/Fznamznon approved this pull request.


https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-04-05 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-26 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk closed 
https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-19 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk deleted 
https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-19 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-19 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-19 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-17 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk deleted 
https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-17 Thread Oleksandr T. via cfe-commits 


@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}

a-tarasyuk wrote:

@cor3ntin @Fznamznon could you review these changes? thanks

https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-17 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-15 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-14 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-13 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-12 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk deleted 
https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-12 Thread Oleksandr T. via cfe-commits 


@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}

a-tarasyuk wrote:

@cor3ntin @Fznamznon could you review these changes? thanks

https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-12 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-11 Thread Aaron Ballman via cfe-commits 

https://github.com/AaronBallman edited 
https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-11 Thread Aaron Ballman via cfe-commits 


@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}

AaronBallman wrote:

> the entire binding declaration is used as the diagnostic location, including 
> all binding elements, even when only some of them are actually unused. Is 
> this the expected behavior?

It's the current behavior but I think we could improve it. For example, it 
would be much better in this case to point to each binding declaration that's 
unused as opposed to the whole structured binding. But the behavior for now is 
okay.

https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-11 Thread Aaron Ballman via cfe-commits 

https://github.com/AaronBallman approved this pull request.

LGTM

https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-11 Thread Oleksandr T. via cfe-commits 


@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}

a-tarasyuk wrote:

@cor3ntin @AaronBallman could you review these changes? thanks 

https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-11 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-03-07 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-02-20 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-02-18 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-02-14 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-02-14 Thread Oleksandr T. via cfe-commits 


@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s

a-tarasyuk wrote:

@Fznamznon I've updated. thanks

https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-02-14 Thread Oleksandr T. via cfe-commits 

https://github.com/a-tarasyuk updated 
https://github.com/llvm/llvm-project/pull/127061

>From a76ee008bdb87655da465e21d09c840edecc2b1b Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Thu, 13 Feb 2025 15:24:09 +0200
Subject: [PATCH 1/2] [Clang] emit -Wunused-variable warning for unused
 structured bindings without the [[maybe_unused]] attribute

---
 clang/docs/ReleaseNotes.rst|  2 ++
 clang/lib/Sema/SemaDecl.cpp|  9 +
 clang/test/SemaCXX/unused-bindings.cpp | 17 +
 clang/test/SemaCXX/unused.cpp  |  3 ++-
 4 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/unused-bindings.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 6344c4b36e357..4f20415ec006d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -160,6 +160,8 @@ Bug Fixes to C++ Support
 - Clang is now better at keeping track of friend function template instance 
contexts. (#GH55509)
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
+- Clang now emits the ``-Wunused-variable`` warning when some structured 
bindings are unused
+  and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810)
 
 Bug Fixes to AST Handling
 ^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eedc77ed20a0..19a73a66be5af 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1921,13 +1921,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions 
&LangOpts,
 // For a decomposition declaration, warn if none of the bindings are
 // referenced, instead of if the variable itself is referenced (which
 // it is, by the bindings' expressions).
-bool IsAllPlaceholders = true;
+bool IsAllIgnored = true;
 for (const auto *BD : DD->bindings()) {
-  if (BD->isReferenced() || BD->hasAttr())
+  if (BD->isReferenced())
 return false;
-  IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts);
+  IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) ||
+  BD->hasAttr());
 }
-if (IsAllPlaceholders)
+if (IsAllIgnored)
   return false;
   } else if (!D->getDeclName()) {
 return false;
diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
new file mode 100644
index 0..01f2126133a20
--- /dev/null
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}
+  auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}}
+
+  auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s;
+  auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable 
'[a4, b4]'}}
+  auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable 
'[a5, b5]'}}
+}
+}
diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp
index 1f40c1b1ca903..ab728069f2faf 100644
--- a/clang/test/SemaCXX/unused.cpp
+++ b/clang/test/SemaCXX/unused.cpp
@@ -114,7 +114,8 @@ namespace maybe_unused_binding {
 
 void test() {
   struct X { int a, b; } x;
-  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}}
+  auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute 
specifier sequence attached to a structured binding declaration is a C++2c 
extension}} \
+// expected-warning {{unused variable '[a, 
b]'}}
 }
 
 }

>From c600c2a2378310c3f2fc82edaca66ca80b40284d Mon Sep 17 00:00:00 2001
From: Oleksandr T 
Date: Fri, 14 Feb 2025 13:43:53 +0200
Subject: [PATCH 2/2] update test to use std c++26

---
 clang/test/SemaCXX/unused-bindings.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/unused-bindings.cpp 
b/clang/test/SemaCXX/unused-bindings.cpp
index 01f2126133a20..83250dd4b0a11 100644
--- a/clang/test/SemaCXX/unused-bindings.cpp
+++ b/clang/test/SemaCXX/unused-bindings.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
 
 namespace GH125810 {
 struct S {

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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-02-14 Thread Mariya Podchishchaeva via cfe-commits 


@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s

Fznamznon wrote:

NIT: why not c++26?
```suggestion
// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s
```

https://github.com/llvm/llvm-project/pull/127061
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[clang] [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (PR #127061)

2025-02-13 Thread Oleksandr T. via cfe-commits 


@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2c -Wunused %s
+
+namespace GH125810 {
+struct S {
+  int a, b;
+};
+
+void t(S s) {
+  auto &[_, _] = s;
+  auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}}

a-tarasyuk wrote:

@cor3ntin @AaronBallman Currently, https://godbolt.org/z/911KjMjPY the entire 
binding declaration is used as the diagnostic location, including all binding 
elements, even when only some of them are actually unused. Is this the expected 
behavior?

https://github.com/llvm/llvm-project/pull/127061
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