[clang] [clang-format] Support of TableGen tokens with unary operator like form, bang operators and numeric literals. (PR #78996)

[Hirofumi Nakamura via cfe-commits]

================
@@ -276,13 +276,44 @@ void FormatTokenLexer::tryMergePreviousTokens() {
       return;
     }
   }
-  // TableGen's Multi line string starts with [{
-  if (Style.isTableGen() && tryMergeTokens({tok::l_square, tok::l_brace},
-                                           TT_TableGenMultiLineString)) {
-    // Set again with finalizing. This must never be annotated as other types.
-    Tokens.back()->setFinalizedType(TT_TableGenMultiLineString);
-    Tokens.back()->Tok.setKind(tok::string_literal);
-    return;
+  if (Style.isTableGen()) {
+    // TableGen's Multi line string starts with [{
+    if (tryMergeTokens({tok::l_square, tok::l_brace},
+                       TT_TableGenMultiLineString)) {
+      // Set again with finalizing. This must never be annotated as other types.
+      Tokens.back()->setFinalizedType(TT_TableGenMultiLineString);
+      Tokens.back()->Tok.setKind(tok::string_literal);
+      return;
+    }
+    // TableGen's bang operator is the form !<name>.
+    // !cond is a special case with specific syntax.
+    if (tryMergeTokens({tok::exclaim, tok::identifier},
+                       TT_TableGenBangOperator)) {
+      Tokens.back()->Tok.setKind(tok::identifier);
+      Tokens.back()->Tok.setIdentifierInfo(nullptr);
+      if (Tokens.back()->TokenText == "!cond")
+        Tokens.back()->setFinalizedType(TT_TableGenCondOperator);
+      else
+        Tokens.back()->setFinalizedType(TT_TableGenBangOperator);
+      return;
+    }
+    if (tryMergeTokens({tok::exclaim, tok::kw_if}, TT_TableGenBangOperator)) {
+      // Here, "! if" becomes "!if".  That is, ! captures if even when the space
+      // exists. That is only one possibility in TableGen's syntax.
+      Tokens.back()->Tok.setKind(tok::identifier);
+      Tokens.back()->Tok.setIdentifierInfo(nullptr);
+      Tokens.back()->setFinalizedType(TT_TableGenBangOperator);
+      return;
+    }
+    // +, - with numbers are literals. Not unary operators.
+    if (tryMergeTokens({tok::plus, tok::numeric_constant}, TT_Unknown)) {
+      Tokens.back()->Tok.setKind(tok::numeric_constant);
+      return;
----------------
hnakamura5 wrote:

@mydeveloperday 
Thank you for reviewing this pull request.
Now it comes to 1 week since this PR is started. I want to continue before I forget.
Could you mind accepting or adding some suggestion?
Or if you do not intend neither, can I request another reviewer? 

https://github.com/llvm/llvm-project/pull/78996