[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-21 Thread Valentyn Yukhymenko via cfe-commits 


@@ -13464,6 +13464,14 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S, 
AccessSpecifier AS,
 }
 TemplateParameterList *TemplateParams = TemplateParamLists[0];
 
+// Check shadowing of a template parameter name
+for (NamedDecl *TP : TemplateParams->asArray()) {
+  if (NameInfo.getName() == TP->getDeclName()) {
+DiagnoseTemplateParameterShadow(Name.StartLocation, TP);
+return nullptr;
+  }
+}
+

BaLiKfromUA wrote:

I replaced my initial loop with the removal of `S = S->getDeclParent();`, but, 
as I understand, we are waiting for other folks to comment.

https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-20 Thread Younan Zhang via cfe-commits 


@@ -13464,6 +13464,14 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S, 
AccessSpecifier AS,
 }
 TemplateParameterList *TemplateParams = TemplateParamLists[0];
 
+// Check shadowing of a template parameter name
+for (NamedDecl *TP : TemplateParams->asArray()) {
+  if (NameInfo.getName() == TP->getDeclName()) {
+DiagnoseTemplateParameterShadow(Name.StartLocation, TP);
+return nullptr;
+  }
+}
+

zyn0217 wrote:

So GCC seems to start rejecting this somewhere between 10.2 and 10.3. Is it a 
DR?
https://compiler-explorer.com/z/GEoWGYbbY

https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-20 Thread Younan Zhang via cfe-commits 


@@ -13464,6 +13464,14 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S, 
AccessSpecifier AS,
 }
 TemplateParameterList *TemplateParams = TemplateParamLists[0];
 
+// Check shadowing of a template parameter name
+for (NamedDecl *TP : TemplateParams->asArray()) {
+  if (NameInfo.getName() == TP->getDeclName()) {
+DiagnoseTemplateParameterShadow(Name.StartLocation, TP);
+return nullptr;
+  }
+}
+

zyn0217 wrote:

@cor3ntin @erichkeane 

I don't understand why we were skipping past template parameter scopes even 
prior to @sdkrystian's patch. It doesn't seem very right for this case.

https://github.com/llvm/llvm-project/commit/c1d8d0aa156f651ee48414fa002e9608d6998763#diff-9ced4fa47ee2b9c03b6996ce89a1d131c0f5b71013993bc582209f50d5e934daL13519

https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-20 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA edited 
https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-20 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA edited 
https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-20 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA edited 
https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-20 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA edited 
https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-20 Thread Valentyn Yukhymenko via cfe-commits 


@@ -13464,6 +13464,14 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S, 
AccessSpecifier AS,
 }
 TemplateParameterList *TemplateParams = TemplateParamLists[0];
 
+// Check shadowing of a template parameter name
+for (NamedDecl *TP : TemplateParams->asArray()) {
+  if (NameInfo.getName() == TP->getDeclName()) {
+DiagnoseTemplateParameterShadow(Name.StartLocation, TP);
+return nullptr;
+  }
+}
+

BaLiKfromUA wrote:

Thank you for the review!

I also was with this expectation and made some investigation (but be aware that 
it might not be 100% correct 😛).

According to my debugging, the reason for `LookupName(Previous, S);` at line 
`13425` not seeing template params of alias template is logic on the beginning 
of a function (line `13401`):
```
S = S->getDeclParent();
```

If you remove this line, the behavior mentioned in the issue is successfully 
diagnosed.

Initially, I thought that this logic was important for some other template 
aliasing functionality that I was missing, but I run locally all clang tests 
without this line, and seems like it doesn't.

So I am probably overthinking and we could just remove line `13401` instead of 
implementing this loop.

@zyn0217 Let me know if I am missing something! Otherwise, I will send a fix 
without this loop later today.



https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread Younan Zhang via cfe-commits 


@@ -191,4 +192,4 @@ int g = sfinae_me(); // expected-error{{no matching 
function for call to 's
 
 namespace NullExceptionDecl {
 template auto get = []() { try { } catch(...) {}; return I; }; // 
expected-error{{initializer contains unexpanded parameter pack 'I'}}
-}
+}

zyn0217 wrote:

Please keep a blank line at the EOF

https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread Younan Zhang via cfe-commits 


@@ -13464,6 +13464,14 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S, 
AccessSpecifier AS,
 }
 TemplateParameterList *TemplateParams = TemplateParamLists[0];
 
+// Check shadowing of a template parameter name
+for (NamedDecl *TP : TemplateParams->asArray()) {
+  if (NameInfo.getName() == TP->getDeclName()) {
+DiagnoseTemplateParameterShadow(Name.StartLocation, TP);
+return nullptr;
+  }
+}
+

zyn0217 wrote:

Did you investigate why the if block around line 13428 doesn't work? I would 
have expected it to catch the issue earlier, before the creation of 
TypeAliasDecl.


```cpp
 // Warn about shadowing the name of a template parameter.
  if (Previous.isSingleResult() &&
  Previous.getFoundDecl()->isTemplateParameter()) {
DiagnoseTemplateParameterShadow(Name.StartLocation,Previous.getFoundDecl());
Previous.clear();
  }

```

https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA ready_for_review 
https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA edited 
https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA updated 
https://github.com/llvm/llvm-project/pull/123533

>From e451a8869420d9240f9006eb2adb599a3e6fd9f8 Mon Sep 17 00:00:00 2001
From: Valentyn Yukhymenko 
Date: Sun, 19 Jan 2025 23:13:46 +
Subject: [PATCH] [Clang] Reject declaring an alias template with the same name
 as its template parameter.

Fixes llvm#123423
---
 clang/docs/ReleaseNotes.rst   | 1 +
 clang/lib/Sema/SemaDeclCXX.cpp| 8 
 .../CXX/temp/temp.decls/temp.variadic/fixed-expansion.cpp | 4 ++--
 clang/test/SemaCXX/alias-template.cpp | 5 +++--
 4 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index aa1c02d04f7caa..29e40b4ecab412 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -956,6 +956,7 @@ Bug Fixes to C++ Support
 - Fixed a crash caused by the incorrect construction of template arguments for 
CTAD alias guides when type
   constraints are applied. (#GH122134)
 - Fixed canonicalization of pack indexing types - Clang did not always 
recognized identical pack indexing. (#GH123033)
+- Clang now rejects declaring an alias template with the same name as its 
template parameter. (#GH123423)
 
 
 Bug Fixes to AST Handling
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index a867ed73bd4033..4e43a8397cec4e 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -13464,6 +13464,14 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S, 
AccessSpecifier AS,
 }
 TemplateParameterList *TemplateParams = TemplateParamLists[0];
 
+// Check shadowing of a template parameter name
+for (NamedDecl *TP : TemplateParams->asArray()) {
+  if (NameInfo.getName() == TP->getDeclName()) {
+DiagnoseTemplateParameterShadow(Name.StartLocation, TP);
+return nullptr;
+  }
+}
+
 // Check that we can declare a template here.
 if (CheckTemplateDeclScope(S, TemplateParams))
   return nullptr;
diff --git a/clang/test/CXX/temp/temp.decls/temp.variadic/fixed-expansion.cpp 
b/clang/test/CXX/temp/temp.decls/temp.variadic/fixed-expansion.cpp
index a990c82564aa40..ab4c663d24c7d5 100644
--- a/clang/test/CXX/temp/temp.decls/temp.variadic/fixed-expansion.cpp
+++ b/clang/test/CXX/temp/temp.decls/temp.variadic/fixed-expansion.cpp
@@ -121,8 +121,8 @@ namespace PartialSpecialization {
 
 namespace FixedAliasTemplate {
   template struct S {};
-  template using U = S; // expected-note 
2{{template parameter is declared here}}
-  template U &f(U, Ts...); // expected-error 
2{{pack expansion used as argument for non-pack parameter of alias template}}
+  template using Z = S; // expected-note 
2{{template parameter is declared here}}
+  template Z &f(Z, Ts...); // expected-error 
2{{pack expansion used as argument for non-pack parameter of alias template}}
   S &s1 = f({}, 0, 0.0); // expected-error {{no matching 
function}}
 }
 
diff --git a/clang/test/SemaCXX/alias-template.cpp 
b/clang/test/SemaCXX/alias-template.cpp
index 5189405e23db56..97134d2f3a96ad 100644
--- a/clang/test/SemaCXX/alias-template.cpp
+++ b/clang/test/SemaCXX/alias-template.cpp
@@ -65,7 +65,8 @@ namespace InFunctions {
   template struct S3 { // expected-note {{template parameter is 
declared here}}
 template using T = int; // expected-error {{declaration of 'T' 
shadows template parameter}}
   };
-  template using Z = Z;
+  template // expected-note {{template parameter is declared here}}
+  using Z = Z; // expected-error {{declaration of 'Z' shadows template 
parameter}}
 }
 
 namespace ClassNameRedecl {
@@ -191,4 +192,4 @@ int g = sfinae_me(); // expected-error{{no matching 
function for call to 's
 
 namespace NullExceptionDecl {
 template auto get = []() { try { } catch(...) {}; return I; }; // 
expected-error{{initializer contains unexpanded parameter pack 'I'}}
-}
+}
\ No newline at end of file

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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread via cfe-commits 

llvmbot wrote:




@llvm/pr-subscribers-clang

Author: Valentyn Yukhymenko (BaLiKfromUA)


Changes

Fixes llvm#123423

**How did I test it?**

Modified existing test and checked an example from the issue manually.


---
Full diff: https://github.com/llvm/llvm-project/pull/123533.diff


3 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+1) 
- (modified) clang/lib/Sema/SemaDeclCXX.cpp (+8) 
- (modified) clang/test/SemaCXX/alias-template.cpp (+3-2) 


``diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index aa1c02d04f7caa..29e40b4ecab412 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -956,6 +956,7 @@ Bug Fixes to C++ Support
 - Fixed a crash caused by the incorrect construction of template arguments for 
CTAD alias guides when type
   constraints are applied. (#GH122134)
 - Fixed canonicalization of pack indexing types - Clang did not always 
recognized identical pack indexing. (#GH123033)
+- Clang now rejects declaring an alias template with the same name as its 
template parameter. (#GH123423)
 
 
 Bug Fixes to AST Handling
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index a867ed73bd4033..4e43a8397cec4e 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -13464,6 +13464,14 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S, 
AccessSpecifier AS,
 }
 TemplateParameterList *TemplateParams = TemplateParamLists[0];
 
+// Check shadowing of a template parameter name
+for (NamedDecl *TP : TemplateParams->asArray()) {
+  if (NameInfo.getName() == TP->getDeclName()) {
+DiagnoseTemplateParameterShadow(Name.StartLocation, TP);
+return nullptr;
+  }
+}
+
 // Check that we can declare a template here.
 if (CheckTemplateDeclScope(S, TemplateParams))
   return nullptr;
diff --git a/clang/test/SemaCXX/alias-template.cpp 
b/clang/test/SemaCXX/alias-template.cpp
index 5189405e23db56..97134d2f3a96ad 100644
--- a/clang/test/SemaCXX/alias-template.cpp
+++ b/clang/test/SemaCXX/alias-template.cpp
@@ -65,7 +65,8 @@ namespace InFunctions {
   template struct S3 { // expected-note {{template parameter is 
declared here}}
 template using T = int; // expected-error {{declaration of 'T' 
shadows template parameter}}
   };
-  template using Z = Z;
+  template // expected-note {{template parameter is declared here}}
+  using Z = Z; // expected-error {{declaration of 'Z' shadows template 
parameter}}
 }
 
 namespace ClassNameRedecl {
@@ -191,4 +192,4 @@ int g = sfinae_me(); // expected-error{{no matching 
function for call to 's
 
 namespace NullExceptionDecl {
 template auto get = []() { try { } catch(...) {}; return I; }; // 
expected-error{{initializer contains unexpanded parameter pack 'I'}}
-}
+}
\ No newline at end of file

``




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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA converted_to_draft 
https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA edited 
https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread Valentyn Yukhymenko via cfe-commits 


@@ -65,7 +65,8 @@ namespace InFunctions {
   template struct S3 { // expected-note {{template parameter is 
declared here}}
 template using T = int; // expected-error {{declaration of 'T' 
shadows template parameter}}
   };
-  template using Z = Z;
+  template // expected-note {{template parameter is declared here}}
+  using Z = Z; // expected-error {{declaration of 'Z' shadows template 
parameter}}

BaLiKfromUA wrote:

I am not sure that `InFunctions` is the correct namespace for this test but it 
was here before and I adapted this use case to the new behavior.

https://github.com/llvm/llvm-project/pull/123533
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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread via cfe-commits 

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[clang] [Clang] Reject declaring an alias template with the same name as its template parameter. (PR #123533)

2025-01-19 Thread Valentyn Yukhymenko via cfe-commits 

https://github.com/BaLiKfromUA created 
https://github.com/llvm/llvm-project/pull/123533

Fixes llvm#123423

**How did I test it?**

Modified existing test and checked an example from the issue manually.


>From 0852c8ca587e772d5f851ac0983f43bdeec2ebd5 Mon Sep 17 00:00:00 2001
From: Valentyn Yukhymenko 
Date: Sun, 19 Jan 2025 23:13:46 +
Subject: [PATCH] [Clang] Reject declaring an alias template with the same name
 as its template parameter.

Fixes llvm#123423
---
 clang/docs/ReleaseNotes.rst   | 1 +
 clang/lib/Sema/SemaDeclCXX.cpp| 8 
 clang/test/SemaCXX/alias-template.cpp | 5 +++--
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index aa1c02d04f7caa..29e40b4ecab412 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -956,6 +956,7 @@ Bug Fixes to C++ Support
 - Fixed a crash caused by the incorrect construction of template arguments for 
CTAD alias guides when type
   constraints are applied. (#GH122134)
 - Fixed canonicalization of pack indexing types - Clang did not always 
recognized identical pack indexing. (#GH123033)
+- Clang now rejects declaring an alias template with the same name as its 
template parameter. (#GH123423)
 
 
 Bug Fixes to AST Handling
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index a867ed73bd4033..4e43a8397cec4e 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -13464,6 +13464,14 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S, 
AccessSpecifier AS,
 }
 TemplateParameterList *TemplateParams = TemplateParamLists[0];
 
+// Check shadowing of a template parameter name
+for (NamedDecl *TP : TemplateParams->asArray()) {
+  if (NameInfo.getName() == TP->getDeclName()) {
+DiagnoseTemplateParameterShadow(Name.StartLocation, TP);
+return nullptr;
+  }
+}
+
 // Check that we can declare a template here.
 if (CheckTemplateDeclScope(S, TemplateParams))
   return nullptr;
diff --git a/clang/test/SemaCXX/alias-template.cpp 
b/clang/test/SemaCXX/alias-template.cpp
index 5189405e23db56..97134d2f3a96ad 100644
--- a/clang/test/SemaCXX/alias-template.cpp
+++ b/clang/test/SemaCXX/alias-template.cpp
@@ -65,7 +65,8 @@ namespace InFunctions {
   template struct S3 { // expected-note {{template parameter is 
declared here}}
 template using T = int; // expected-error {{declaration of 'T' 
shadows template parameter}}
   };
-  template using Z = Z;
+  template // expected-note {{template parameter is declared here}}
+  using Z = Z; // expected-error {{declaration of 'Z' shadows template 
parameter}}
 }
 
 namespace ClassNameRedecl {
@@ -191,4 +192,4 @@ int g = sfinae_me(); // expected-error{{no matching 
function for call to 's
 
 namespace NullExceptionDecl {
 template auto get = []() { try { } catch(...) {}; return I; }; // 
expected-error{{initializer contains unexpanded parameter pack 'I'}}
-}
+}
\ No newline at end of file

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