Add support for nested namespaces (C++17)

Task-number: QTCREATORBUG-16774
Change-Id: I3de3ac65810213e21c9a3bafef2474d252e191f7
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/libs/3rdparty/cplusplus/Parser.cpp

@@ -863,7 +863,8 @@ bool Parser::parseStaticAssertDeclaration(DeclarationAST *&node)
 bool Parser::parseNamespace(DeclarationAST *&node)
 {
     DEBUG_THIS_RULE();
-    if (LA() != T_NAMESPACE && !(_languageFeatures.cxx11Enabled && LA() == T_INLINE && LA(2) == T_NAMESPACE))
+    if (LA() != T_NAMESPACE && !(_languageFeatures.cxx11Enabled && LA() == T_INLINE && LA(2) == T_NAMESPACE)
+            && !isNestedNamespace())
         return false;
 
     unsigned inline_token = 0;
@@ -892,7 +893,9 @@ bool Parser::parseNamespace(DeclarationAST *&node)
     if (LA() == T_IDENTIFIER)
         ast->identifier_token = consumeToken();
     parseOptionalAttributeSpecifierSequence(ast->attribute_list);
-    if (LA() == T_LBRACE) {
+    if (isNestedNamespace()) {
+        parseNestedNamespace(ast->linkage_body);
+    } else if (LA() == T_LBRACE) {
         parseLinkageBody(ast->linkage_body);
     } else { // attempt to do error recovery
         unsigned pos = cursor();
@@ -923,6 +926,22 @@ bool Parser::parseNamespace(DeclarationAST *&node)
     return true;
 }
 
+bool Parser::isNestedNamespace() const
+{
+    return _languageFeatures.cxx11Enabled && LA() == T_COLON_COLON && LA(2) == T_IDENTIFIER;
+}
+
+bool Parser::parseNestedNamespace(DeclarationAST *&node)
+{
+    DEBUG_THIS_RULE();
+    DeclarationAST *ast = 0;
+    if (isNestedNamespace() && parseNamespace(ast)) {
+        node = ast;
+        return true;
+    }
+    return false;
+}
+
 bool Parser::parseUsing(DeclarationAST *&node)
 {
     DEBUG_THIS_RULE();

src/libs/3rdparty/cplusplus/Parser.h

@@ -119,6 +119,7 @@ public:
     bool parseNestedNameSpecifierOpt(NestedNameSpecifierListAST *&name, bool acceptTemplateId);
     bool parseStaticAssertDeclaration(DeclarationAST *&node);
     bool parseNamespace(DeclarationAST *&node);
+    bool parseNestedNamespace(DeclarationAST *&node);
     bool parseNamespaceAliasDefinition(DeclarationAST *&node);
     bool parseNewArrayDeclarator(NewArrayDeclaratorListAST *&node);
     bool parseNewExpression(ExpressionAST *&node);
@@ -332,6 +333,8 @@ private:
 private:
     Parser(const Parser& source);
     void operator =(const Parser& source);
+
+    bool isNestedNamespace() const;
 };
 
 } // namespace CPlusPlus

tests/auto/cplusplus/cxx11/cxx11.pro

@@ -7,6 +7,8 @@ SOURCES += tst_cxx11.cpp
 DISTFILES += \
     data/inlineNamespace.1.cpp \
     data/inlineNamespace.1.errors.txt \
+    data/nestedNamespace.1.cpp \
+    data/nestedNamespace.1.errors.txt \
     data/staticAssert.1.cpp \
     data/staticAssert.1.errors.txt \
     data/noExcept.1.cpp \

tests/auto/cplusplus/cxx11/data/nestedNamespace.1.cpp

@@ -0,0 +1,7 @@
+
+namespace A::B::C {
+    class Foo {
+
+    };
+}
+

tests/auto/cplusplus/cxx11/tst_cxx11.cpp

@@ -176,6 +176,7 @@ void tst_cxx11::parse_data()
     QTest::addColumn<QString>("errorFile");
 
     QTest::newRow("inlineNamespace.1") << "inlineNamespace.1.cpp" << "inlineNamespace.1.errors.txt";
+    QTest::newRow("nestedNamespace.1") << "nestedNamespace.1.cpp" << "nestedNamespace.1.errors.txt";
     QTest::newRow("staticAssert.1") << "staticAssert.1.cpp" << "staticAssert.1.errors.txt";
     QTest::newRow("noExcept.1") << "noExcept.1.cpp" << "noExcept.1.errors.txt";
     QTest::newRow("braceInitializers.1") << "braceInitializers.1.cpp" << "braceInitializers.1.errors.txt";