C++23 multidimensional subscript operator

- [multidimensional subscript operator](https://en.cppreference.com/w/cpp/language/operators#Array_subscr) [P2128R6](https://wg21.link/P2128R6) - linked SonarOpenCommunity#2536
guwirth · Aug 29, 2024 · 993f5b6 · 993f5b6
1 parent 696d8f3
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diff --git a/cxx-squid/dox/2023-03-19_cpp23_grammar.txt b/cxx-squid/dox/2023-03-19_cpp23_grammar.txt
@@ -436,8 +436,7 @@ nested-name-specifier:
 
 lambda-expression:
    lambda-introducer attribute-specifier-seqopt lambda-declarator compound-statement
-   lambda-introducer < template-parameter-list > requires-clauseopt attribute-specifier-seqopt
-   lambda-declarator compound-statement
+   lambda-introducer < template-parameter-list > requires-clauseopt attribute-specifier-seqopt lambda-declarator compound-statement
 
 lambda-introducer:
    [ lambda-captureopt ]
@@ -446,8 +445,7 @@ lambda-declarator:
    lambda-specifier-seq noexcept-specifieropt attribute-specifier-seqopt trailing-return-typeopt
    noexcept-specifier attribute-specifier-seqopt trailing-return-typeopt
    trailing-return-typeopt
-   ( parameter-declaration-clause ) lambda-specifier-seqopt noexcept-specifieropt attribute-specifier-seqopt
-   trailing-return-typeopt requires-clauseopt
+   ( parameter-declaration-clause ) lambda-specifier-seqopt noexcept-specifieropt attribute-specifier-seqopt trailing-return-typeopt requires-clauseopt
 
 lambda-specifier:
    consteval

diff --git a/cxx-squid/dox/diff-cpp20-cpp23_grammar.txt b/cxx-squid/dox/diff-cpp20-cpp23_grammar.txt
@@ -136,15 +136,16 @@ d-char:
 
 lambda-expression:
    lambda-introducer attribute-specifier-seqopt lambda-declarator compound-statement
-   lambda-introducer < template-parameter-list > requires-clauseopt attribute-specifier-seqopt
-   lambda-declarator compound-statement
+   lambda-introducer < template-parameter-list > requires-clauseopt attribute-specifier-seqopt lambda-declarator compound-statement
+
+lambda-introducer:
+   [ lambda-captureopt ]
 
 lambda-declarator:
    lambda-specifier-seq noexcept-specifieropt attribute-specifier-seqopt trailing-return-typeopt
    noexcept-specifier attribute-specifier-seqopt trailing-return-typeopt
    trailing-return-typeopt
-   ( parameter-declaration-clause ) lambda-specifier-seqopt noexcept-specifieropt attribute-specifier-seqopt
-   trailing-return-typeopt requires-clauseopt
+   ( parameter-declaration-clause ) lambda-specifier-seqopt noexcept-specifieropt attribute-specifier-seqopt trailing-return-typeopt requires-clauseopt
 
 lambda-specifier:
    consteval
@@ -163,25 +164,6 @@ requirement-seq:
    requirement
    requirement requirement-seq
 
-postfix-expression:
-   primary-expression
-   postfix-expression [ expression-listopt ]
-   postfix-expression ( expression-listopt )
-   simple-type-specifier ( expression-listopt )
-   typename-specifier ( expression-listopt )
-   simple-type-specifier braced-init-list
-   typename-specifier braced-init-list
-   postfix-expression . templateopt id-expression
-   postfix-expression -> templateopt id-expression
-   postfix-expression ++
-   postfix-expression --
-   dynamic_cast < type-id > ( expression )
-   static_cast < type-id > ( expression )
-   reinterpret_cast < type-id > ( expression )
-   const_cast < type-id > ( expression )
-   typeid ( expression )
-   typeid ( type-id )
-
 **A.6 Statements [gram.stmt]**
 
 init-statement:

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
@@ -697,7 +697,7 @@ private static void expressions(LexerfulGrammarBuilder b) {
       ),
       b.zeroOrMore(
         b.firstOf(
-          b.sequence("[", exprOrBracedInitList, "]"), // C++
+          b.sequence("[", b.optional(expressionList), "]"), // C++23
           b.sequence("(", b.optional(expressionList), ")"), // C++
           b.sequence(
             b.firstOf(

diff --git a/cxx-squid/src/test/java/org/sonar/cxx/parser/ExpressionTest.java b/cxx-squid/src/test/java/org/sonar/cxx/parser/ExpressionTest.java
@@ -296,7 +296,6 @@ void postfixExpression() {
     mockRule(CxxGrammarImpl.expression);
     mockRule(CxxGrammarImpl.idExpression);
     mockRule(CxxGrammarImpl.typeId);
-    mockRule(CxxGrammarImpl.exprOrBracedInitList);
     mockRule(CxxGrammarImpl.cudaKernel);
 
     assertThatParser()
@@ -313,7 +312,8 @@ void postfixExpression() {
       .matches("const_cast < typeId > ( expression )")
       .matches("typeid ( expression )")
       .matches("typeid ( typeId )")
-      .matches("primaryExpression [ exprOrBracedInitList ]")
+      .matches("primaryExpression [ ]") // C++23
+      .matches("primaryExpression [ expressionList ]") // C++23
       .matches("primaryExpression ( )")
       .matches("primaryExpression ( expressionList )")
       .matches("primaryExpression . idExpression")
@@ -342,7 +342,9 @@ void postfixExpression_reallife() {
       .matches("G::typeid")
       .matches("int::typeid")
       // CUDA
-      .matches("kernel<<<gridDim,blockDim,0>>>(d_data, height, width)");
+      .matches("kernel<<<gridDim,blockDim,0>>>(d_data, height, width)")
+      // C++23
+      .matches("array[a, b]");
   }
 
   @Test

diff --git a/cxx-squid/src/test/resources/parser/own/C++23/multidimensional-subscript-operator.cc b/cxx-squid/src/test/resources/parser/own/C++23/multidimensional-subscript-operator.cc
@@ -0,0 +1,25 @@
+template<typename T, std::size_t X, std::size_t Y>
+struct Matrix {
+
+    static inline std::array<T, X * Y> mat{};               // (2)
+
+    static T& operator[](std::size_t x, std::size_t y) {    // (1)
+        return mat[y * X + x];
+    }
+};
+
+int main() {
+
+    std::cout << '\n';
+
+    Matrix<int, 3, 3> mat;
+    for (auto i : {0, 1, 2}) {
+        for (auto j : {0, 1, 2}) mat[i, j] = (i * 3) + j;
+    }
+    for (auto i : {0, 1, 2}) {
+        for (auto j : {0, 1, 2}) std::cout << mat[i, j] << " ";
+    }
+
+    std::cout << '\n';
+
+}