https://github.com/zyn0217 updated
https://github.com/llvm/llvm-project/pull/116332
>From 5973de1d4c368a26fd179954a13de94595f35575 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7...@gmail.com>
Date: Fri, 15 Nov 2024 14:09:14 +0800
Subject: [PATCH 1/2] [Clang][Parser] Make 'T...[N]' within a function
parameter a valid pack expansion prior to C++2c
---
.../clang/Basic/DiagnosticParseKinds.td | 5 ++++
clang/lib/Parse/ParseExprCXX.cpp | 18 ++++++++++++++
.../CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp | 5 ++--
clang/test/Parser/cxx0x-decl.cpp | 8 ++-----
.../SemaCXX/cxx2c-pack-indexing-ext-diags.cpp | 24 +++++++++++++++++++
5 files changed, 52 insertions(+), 8 deletions(-)
diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td
b/clang/include/clang/Basic/DiagnosticParseKinds.td
index 0da509280068ad..7b408f3eed5ba5 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -718,6 +718,11 @@ def warn_empty_init_statement : Warning<
"has no effect">, InGroup<EmptyInitStatement>, DefaultIgnore;
def err_keyword_as_parameter : Error <
"invalid parameter name: '%0' is a keyword">;
+def warn_pre_cxx26_ambiguous_pack_indexing_type : Warning<
+ "parameter packs without specifying a name would become a pack indexing "
+ "declaration in C++2c onwards">, InGroup<CXXPre26Compat>;
+def note_add_a_name_to_pre_cxx26_parameter_packs : Note<
+ "add a name to disambiguate">;
// C++ derived classes
def err_dup_virtual : Error<"duplicate 'virtual' in base specifier">;
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index ce3624f366a2a1..c596785b267b5b 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -242,7 +242,25 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
SourceLocation Start = Tok.getLocation();
DeclSpec DS(AttrFactory);
SourceLocation CCLoc;
+ TentativeParsingAction MaybePackIndexing(*this, /*Unannotated=*/true);
SourceLocation EndLoc = ParsePackIndexingType(DS);
+ // C++ [cpp23.dcl.dcl-2]:
+ // Previously, T...[n] would declare a pack of function parameters.
+ // T...[n] is now a pack-index-specifier. [...] Valid C++ 2023 code that
+ // declares a pack of parameters without specifying a declarator-id
+ // becomes ill-formed.
+ if (!Tok.is(tok::coloncolon) && !getLangOpts().CPlusPlus26 &&
+ getCurScope()->isFunctionDeclarationScope()) {
+ Diag(DS.getEllipsisLoc(),
+ diag::warn_pre_cxx26_ambiguous_pack_indexing_type);
+ Diag(DS.getEllipsisLoc(),
+ diag::note_add_a_name_to_pre_cxx26_parameter_packs);
+ MaybePackIndexing.Revert();
+ return false;
+ }
+
+ MaybePackIndexing.Commit();
+
if (DS.getTypeSpecType() == DeclSpec::TST_error)
return false;
diff --git a/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp
b/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp
index dbb6e60d9b93d7..0ae08da280b152 100644
--- a/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp
+++ b/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp
@@ -58,8 +58,9 @@ void b(T[] ...);
template<typename T>
void c(T ... []); // expected-error {{expected expression}} \
- // expected-error {{'T' does not refer to the name of a
parameter pack}} \
- // expected-warning {{pack indexing is a C++2c extension}}
+ // expected-error {{type 'T[]' of function parameter pack
does not contain any unexpanded parameter packs}} \
+ // expected-warning {{would become a pack indexing
declaration in C++2c onwards}} \
+ // expected-note {{add a name to disambiguate}}
template<typename T>
void d(T ... x[]); // expected-error{{type 'T[]' of function parameter pack
does not contain any unexpanded parameter packs}}
diff --git a/clang/test/Parser/cxx0x-decl.cpp b/clang/test/Parser/cxx0x-decl.cpp
index a0b3266c738ff5..91b97df459df92 100644
--- a/clang/test/Parser/cxx0x-decl.cpp
+++ b/clang/test/Parser/cxx0x-decl.cpp
@@ -214,12 +214,8 @@ struct MemberComponentOrder : Base {
void NoMissingSemicolonHere(struct S
[3]);
template<int ...N> void NoMissingSemicolonHereEither(struct S... [N]);
-// expected-error@-1 {{'S' does not refer to the name of a parameter pack}} \
-// expected-error@-1 {{declaration of anonymous struct must be a definition}} \
-// expected-error@-1 {{expected parameter declarator}} \
-// expected-error@-1 {{pack indexing is a C++2c extension}} \
-
-
+// expected-warning@-1 {{parameter packs without specifying a name would
become a pack indexing declaration in C++2c onwards}} \
+// expected-note@-1 {{add a name to disambiguate}}
// This must be at the end of the file; we used to look ahead past the EOF
token here.
// expected-error@+1 {{expected unqualified-id}} expected-error@+1{{expected
';'}}
diff --git a/clang/test/SemaCXX/cxx2c-pack-indexing-ext-diags.cpp
b/clang/test/SemaCXX/cxx2c-pack-indexing-ext-diags.cpp
index 80dfeb9b6a8bf5..f4dbd5ca539635 100644
--- a/clang/test/SemaCXX/cxx2c-pack-indexing-ext-diags.cpp
+++ b/clang/test/SemaCXX/cxx2c-pack-indexing-ext-diags.cpp
@@ -19,3 +19,27 @@ void f(T... t) {
// cxx11-warning@+1 {{pack indexing is a C++2c extension}}
T...[0] c;
}
+
+template <typename... T>
+void g(T... [1]); // cxx11-warning {{parameter packs without specifying a name
would become a pack indexing declaration in C++2c onwards}} \
+ // cxx11-note {{add a name to disambiguate}} \
+ // cxx26-warning {{pack indexing is incompatible with C++
standards before C++2c}} \
+ // cxx26-note {{candidate function template not viable}}
+
+template <typename... T>
+void h(T... param[1]);
+
+template <class T>
+struct S {
+ using type = T;
+};
+
+template <typename... T>
+void h(typename T... [1]::type); // cxx11-warning {{pack indexing is a C++2c
extension}} \
+ // cxx26-warning {{pack indexing is
incompatible with C++ standards before C++2c}}
+
+void call() {
+ g<int, double>(nullptr, nullptr); // cxx26-error {{no matching function for
call to 'g'}}
+ h<int, double>(nullptr, nullptr);
+ h<S<int>, S<const char *>>("hello");
+}
>From c48988ae40d6a6934a75b527cb9d3d4a42de1faa Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7...@gmail.com>
Date: Sat, 16 Nov 2024 21:24:41 +0800
Subject: [PATCH 2/2] Accept 'T...[]' within a function parameter scope
---
clang/lib/Parse/ParseExprCXX.cpp | 3 ++-
clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp | 9 +++++----
clang/test/Parser/cxx2c-pack-indexing.cpp | 5 ++---
3 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index c596785b267b5b..66ba5e2cd074c3 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -238,7 +238,8 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
else if (!HasScopeSpecifier && Tok.is(tok::identifier) &&
GetLookAheadToken(1).is(tok::ellipsis) &&
- GetLookAheadToken(2).is(tok::l_square)) {
+ GetLookAheadToken(2).is(tok::l_square) &&
+ !GetLookAheadToken(3).is(tok::r_square)) {
SourceLocation Start = Tok.getLocation();
DeclSpec DS(AttrFactory);
SourceLocation CCLoc;
diff --git a/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp
b/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp
index 0ae08da280b152..a633c108bc22cd 100644
--- a/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp
+++ b/clang/test/CXX/dcl.decl/dcl.meaning/dcl.fct/p13.cpp
@@ -57,10 +57,11 @@ template<typename T>
void b(T[] ...);
template<typename T>
-void c(T ... []); // expected-error {{expected expression}} \
- // expected-error {{type 'T[]' of function parameter pack
does not contain any unexpanded parameter packs}} \
- // expected-warning {{would become a pack indexing
declaration in C++2c onwards}} \
- // expected-note {{add a name to disambiguate}}
+void c(T ... []); // expected-error {{type 'T[]' of function parameter pack
does not contain any unexpanded parameter packs}}
+
+// A function that takes pointers to each type T as arguments, after any decay.
+template <typename ...T>
+void g(T...[]);
template<typename T>
void d(T ... x[]); // expected-error{{type 'T[]' of function parameter pack
does not contain any unexpanded parameter packs}}
diff --git a/clang/test/Parser/cxx2c-pack-indexing.cpp
b/clang/test/Parser/cxx2c-pack-indexing.cpp
index c279bdd7af8c44..45a0e047221e1f 100644
--- a/clang/test/Parser/cxx2c-pack-indexing.cpp
+++ b/clang/test/Parser/cxx2c-pack-indexing.cpp
@@ -12,8 +12,7 @@ struct S {
// expected-note {{to match this '['}} \
// expected-warning{{declaration does not declare anything}}
- T...[]; // expected-error{{expected expression}} \
- // expected-warning{{declaration does not declare anything}}
+ T...[]; // expected-error{{expected member name or ';' after declaration
specifiers}}
void f(auto... v) {
decltype(v...[1]) a = v...[1];
@@ -65,7 +64,7 @@ int main() {
}
-namespace GH11460 {
+namespace GH111460 {
template <typename... T>
requires( ); // expected-error {{expected expression}}
struct SS {
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