Fix #14400 FP syntaxError for trailing return type

lib/tokenize.cpp

@@ -103,14 +103,14 @@ static void skipEnumBody(T *&tok)
 /**
  * is tok the start brace { of a class, struct, union, or enum
  */
-static bool isClassStructUnionEnumStart(const Token * tok)
+static const Token* isClassStructUnionEnumStart(const Token * tok)
 {
     if (!Token::Match(tok->previous(), "class|struct|union|enum|%name%|>|>> {"))
-        return false;
+        return nullptr;
     const Token * tok2 = tok->previous();
     while (tok2 && !Token::Match(tok2, "class|struct|union|enum|{|}|)|;|>|>>"))
         tok2 = tok2->previous();
-    return Token::Match(tok2, "class|struct|union|enum");
+    return Token::Match(tok2, "class|struct|union|enum") ? tok2 : nullptr;
 }
 
 //---------------------------------------------------------------------------
@@ -8783,12 +8783,16 @@ void Tokenizer::findGarbageCode() const
             syntaxError(tok, "keyword '" + tok->str() + "' is not allowed in global scope");
     }
     for (const Token *tok = tokens(); tok; tok = tok->next()) {
-        if (tok->str() == "{" && isClassStructUnionEnumStart(tok)) {
-            for (const Token* tok2 = tok->next(); tok2 != tok->link(); tok2 = tok2->next()) {
-                if (tok2->str() == "{")
-                    tok2 = tok2->link();
-                else if (tok2->isKeyword() && nonGlobalKeywords.count(tok2->str()) && !Token::Match(tok2->tokAt(-2), "operator %str%"))
-                    syntaxError(tok2, "keyword '" + tok2->str() + "' is not allowed in class/struct/union/enum scope");
+        if (tok->str() == "{") {
+            if (const Token* start = isClassStructUnionEnumStart(tok)) {
+                if (Token::simpleMatch(start->tokAt(-1), "->"))
+                    continue;
+                for (const Token* tok2 = tok->next(); tok2 != tok->link(); tok2 = tok2->next()) {
+                    if (tok2->str() == "{")
+                        tok2 = tok2->link();
+                    else if (tok2->isKeyword() && nonGlobalKeywords.count(tok2->str()) && !Token::Match(tok2->tokAt(-2), "operator %str%"))
+                        syntaxError(tok2, "keyword '" + tok2->str() + "' is not allowed in class/struct/union/enum scope");
+                }
             }
         }
     }

test/testtokenize.cpp

@@ -7683,6 +7683,12 @@ class TestTokenizer : public TestFixture {
 
         ASSERT_NO_THROW(tokenizeAndStringify("struct S { unsigned u:2, :30; };")); // #14393
 
+        ASSERT_NO_THROW(tokenizeAndStringify("struct S {};\n" // #14400
+                                             "auto f(bool b) -> struct S {\n"
+                                             "    if (b) {}\n"
+                                             "    return {};\n"
+                                             "};\n"));
+
         ignore_errout();
     }