Fix #14400 FP syntaxError for trailing return type (danmar#8127)

Co-authored-by: chrchr-github <noreply@github.com>

Author: chrchr-github

lib/tokenize.cpp

@@ -110,7 +110,7 @@ static bool isClassStructUnionEnumStart(const Token * tok)
     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") && !Token::simpleMatch(tok2->tokAt(-1), "->");
 }
 
 //---------------------------------------------------------------------------

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();
     }