Fix #12218 syntaxError with typedef in namespace (#5694)

Author: chrchr-github

lib/tokenize.cpp

@@ -1942,6 +1942,8 @@ void Tokenizer::simplifyTypedefCpp()
                         tok2 = tok2->next();
                         tok2->next()->insertToken("0");
                     }
+                    if (Token::Match(tok2->tokAt(-1), "class|struct|union") && tok2->strAt(-1) == typeStart->str())
+                        tok2->deletePrevious();
                     tok2->str(typeStart->str());
 
                     // restore qualification if it was removed

test/testsimplifytypedef.cpp

@@ -212,6 +212,7 @@ class TestSimplifyTypedef : public TestFixture {
         TEST_CASE(simplifyTypedef146);
         TEST_CASE(simplifyTypedef147);
         TEST_CASE(simplifyTypedef148);
+        TEST_CASE(simplifyTypedef149);
 
         TEST_CASE(simplifyTypedefFunction1);
         TEST_CASE(simplifyTypedefFunction2); // ticket #1685
@@ -3443,6 +3444,18 @@ class TestSimplifyTypedef : public TestFixture {
         ASSERT_EQUALS("int & r = i ;", tok(code));
     }
 
+    void simplifyTypedef149() { // #12218
+        const char* code{};
+        code = "namespace N {\n"
+               "    typedef struct S {} S;\n"
+               "}\n"
+               "void g(int);\n"
+               "void f() {\n"
+               "    g(sizeof(struct N::S));\n"
+               "}\n";
+        ASSERT_EQUALS("namespace N { struct S { } ; } void g ( int ) ; void f ( ) { g ( sizeof ( struct N :: S ) ) ; }", tok(code));
+    }
+
     void simplifyTypedefFunction1() {
         {
             const char code[] = "typedef void (*my_func)();\n"