[lld] [ELF] Add VersionNode lexer state for better version script parsing (PR #174530)

[Peter Smith via llvm-commits]

================
@@ -124,29 +124,37 @@ void ScriptLexer::lex() {
       return;
     }
 
-    // Some operators form separate tokens.
-    if (s.starts_with("<<=") || s.starts_with(">>=")) {
-      curTok = s.substr(0, 3);
-      s = s.substr(3);
-      return;
-    }
-    if (s.size() > 1 && (s[1] == '=' && strchr("+-*/!&^|", s[0]))) {
-      curTok = s.substr(0, 2);
-      s = s.substr(2);
-      return;
-    }
+    // In Script and Expr states, recognize compound assignment operators.
+    auto doAssign = [&]() -> std::optional<StringRef> {
+      if (s.starts_with("<<=") || s.starts_with(">>=")) {
+        curTok = s.substr(0, 3);
+        s = s.substr(3);
+        return s;
+      }
+      if (s.size() > 1 && (s[1] == '=' && strchr("+-*/!&^|", s[0]))) {
+        curTok = s.substr(0, 2);
+        s = s.substr(2);
+        return s;
+      }
+      return {};
+    };
 
     // Unquoted token. The non-expression token is more relaxed than tokens in
     // C-like languages, so that you can write "file-name.cpp" as one bare
     // token.
     size_t pos;
+    constexpr StringRef scriptChars =
----------------
smithp35 wrote:

perhaps `scriptAndVersionChars` or perhaps have a separate
```
constexpr StringRef exprChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
          "0123456789_.$"
```


https://github.com/llvm/llvm-project/pull/174530