C++23 deducing this

- [Explicit object parameter (deducing this)](https://en.cppreference.com/w/cpp/language/member_functions#Expli) [P0847R7](https://wg21.link/P0847R7) - linked SonarOpenCommunity#2536
guwirth · Aug 28, 2024 · c60c634 · c60c634
1 parent 41ab59e
commit c60c634
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Showing 4 changed files with 46 additions and 10 deletions.
diff --git a/cxx-squid/dox/diff-cpp20-cpp23_grammar.txt b/cxx-squid/dox/diff-cpp20-cpp23_grammar.txt
@@ -240,12 +240,6 @@ elaborated-type-specifier:
    class-key nested-name-specifier templateopt simple-template-id
    enum nested-name-specifieropt identifier
 
-parameter-declaration:
-   attribute-specifier-seqopt thisopt decl-specifier-seq declarator
-   attribute-specifier-seqopt decl-specifier-seq declarator = initializer-clause
-   attribute-specifier-seqopt thisopt decl-specifier-seq abstract-declaratoropt
-   attribute-specifier-seqopt decl-specifier-seq abstract-declaratoropt = initializer-clause
-
 using-enum-declaration:
    using enum using-enum-declarator ;
 

diff --git a/cxx-squid/src/main/java/org/sonar/cxx/parser/CxxGrammarImpl.java b/cxx-squid/src/main/java/org/sonar/cxx/parser/CxxGrammarImpl.java
@@ -1428,10 +1428,10 @@ private static void declarations(LexerfulGrammarBuilder b) {
         // sample: template<bool x=false> string f();
         b.sequence(b.optional(attributeSpecifierSeq), parameterDeclSpecifierSeq, declarator,
                    "=", LITERAL), // syntax sugar
-        b.sequence(b.optional(attributeSpecifierSeq), b.optional(vcAtlAttribute), parameterDeclSpecifierSeq, declarator,
-                   b.optional("=", initializerClause)), // C++
-        b.sequence(b.optional(attributeSpecifierSeq), parameterDeclSpecifierSeq, b.optional(abstractDeclarator),
-                   b.optional("=", initializerClause))) // C++
+        b.sequence(b.optional(attributeSpecifierSeq), b.optional(CxxKeyword.THIS), b.optional(vcAtlAttribute),
+                   parameterDeclSpecifierSeq, declarator, b.optional("=", initializerClause)), // C++
+        b.sequence(b.optional(attributeSpecifierSeq), b.optional(CxxKeyword.THIS), parameterDeclSpecifierSeq,
+                   b.optional(abstractDeclarator), b.optional("=", initializerClause))) // C++
     );
 
     b.rule(parameterDeclSpecifierSeq).is( // is decl-specifier-seq

diff --git a/cxx-squid/src/test/java/org/sonar/cxx/parser/DeclaratorsTest.java b/cxx-squid/src/test/java/org/sonar/cxx/parser/DeclaratorsTest.java
@@ -410,12 +410,18 @@ void parameterDeclaration() {
 
     assertThatParser()
       .matches("parameterDeclSpecifierSeq declarator")
+      .matches("this parameterDeclSpecifierSeq declarator")
       .matches("attributeSpecifierSeq parameterDeclSpecifierSeq declarator")
+      .matches("attributeSpecifierSeq this parameterDeclSpecifierSeq declarator")
       .matches("parameterDeclSpecifierSeq declarator = initializerClause")
       .matches("attributeSpecifierSeq parameterDeclSpecifierSeq declarator = initializerClause")
       .matches("parameterDeclSpecifierSeq")
+      .matches("this parameterDeclSpecifierSeq")
+      .matches("attributeSpecifierSeq this parameterDeclSpecifierSeq")
       .matches("parameterDeclSpecifierSeq abstractDeclarator")
+      .matches("this parameterDeclSpecifierSeq abstractDeclarator")
       .matches("attributeSpecifierSeq parameterDeclSpecifierSeq abstractDeclarator")
+      .matches("attributeSpecifierSeq this parameterDeclSpecifierSeq abstractDeclarator")
       .matches("parameterDeclSpecifierSeq = initializerClause")
       .matches("parameterDeclSpecifierSeq abstractDeclarator = initializerClause")
       .matches("attributeSpecifierSeq parameterDeclSpecifierSeq abstractDeclarator = initializerClause");
@@ -433,6 +439,9 @@ void parameterDeclaration_reallife() {
       .matches("string")
       .matches("::P& c")
       .matches("bool (A::*bar)(void)")
+      // C++23
+      .matches("this Self&& self")
+      .matches("this Y const&")
       // CLI extension
       .matches("const int^ i")
       .matches("const int% i")

diff --git a/cxx-squid/src/test/resources/parser/own/C++23/deducing-this.cc b/cxx-squid/src/test/resources/parser/own/C++23/deducing-this.cc
@@ -0,0 +1,33 @@
+struct X {
+    void foo(this X const& self, int i); // same as void foo(int i) const &;
+//  void foo(int i) const &; // Error: already declared
+    void bar(this X self, int i); // pass object by value: makes a copy of “*this”
+};
+
+struct Y {
+    template<typename Self>
+    void foo(this Self&&, int);
+};
+
+struct D : Y {};
+
+void ex(Y& y, D& d)
+{
+    y.foo(1);       // Self = Y&
+    move(x).foo(2); // Self = Y
+    d.foo(3);       // Self = D&
+}
+
+// a CRTP trait
+struct add_postfix_increment {
+    template<typename Self>
+    auto operator++(this Self&& self, int) {
+        auto tmp = self; // Self deduces to "some_type"
+        ++self;
+        return tmp;
+    }
+};
+
+struct some_type : add_postfix_increment {
+    some_type& operator++() { /*...*/ }
+};