Fix #12571 debug: valueFlowBailoutIncompleteVar with trailing return type (#6229)

Author: chrchr-github

lib/symboldatabase.cpp

@@ -1554,6 +1554,9 @@ void SymbolDatabase::createSymbolDatabaseIncompleteVars()
                 parent = parent->astParent();
             if (Token::simpleMatch(parent, "new"))
                 continue;
+            // trailing return type
+            if (Token::simpleMatch(ftok, ".") && ftok->originalName() == "->" && Token::Match(ftok->tokAt(-1), "[])]"))
+                continue;
         }
         tok->isIncompleteVar(true);
     }

test/testsymboldatabase.cpp

@@ -5845,6 +5845,16 @@ class TestSymbolDatabase : public TestFixture {
             const Token* r = Token::findsimplematch(q, "r");
             ASSERT(r && !r->isIncompleteVar());
         }
+        {
+            GET_SYMBOL_DB("void f() {\n" // #12571
+                          "    auto g = []() -> std::string* {\n"
+                          "        return nullptr;\n"
+                          "    };\n"
+                          "}\n");
+            ASSERT(db && errout_str().empty());
+            const Token* s = Token::findsimplematch(tokenizer.tokens(), "string");
+            ASSERT(s && !s->isIncompleteVar());
+        }
     }
 
     void enum1() {