[clang-tidy] Support expressions of literals in modernize-macro-to-enum

Add a recursive descent parser to match macro expansion tokens against
fully formed valid expressions of integral literals.  Partial
expressions will not be matched -- they can't be valid initializing
expressions for an enum.

Differential Revision: https://reviews.llvm.org/D124500

Fixes #55055

clang-tools-extra/clang-tidy/modernize/CMakeLists.txt

@@ -9,6 +9,7 @@ add_clang_library(clangTidyModernizeModule
   ConcatNestedNamespacesCheck.cpp
   DeprecatedHeadersCheck.cpp
   DeprecatedIosBaseAliasesCheck.cpp
+  IntegralLiteralExpressionMatcher.cpp
   LoopConvertCheck.cpp
   LoopConvertUtils.cpp
   MacroToEnumCheck.cpp

clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.cpp

@@ -0,0 +1,232 @@
+//===--- IntegralLiteralExpressionMatcher.cpp - clang-tidy ----------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "IntegralLiteralExpressionMatcher.h"
+
+#include <cctype>
+#include <stdexcept>
+
+namespace clang {
+namespace tidy {
+namespace modernize {
+
+// Validate that this literal token is a valid integer literal.  A literal token
+// could be a floating-point token, which isn't acceptable as a value for an
+// enumeration.  A floating-point token must either have a decimal point or an
+// exponent ('E' or 'P').
+static bool isIntegralConstant(const Token &Token) {
+  const char *Begin = Token.getLiteralData();
+  const char *End = Begin + Token.getLength();
+
+  // Not a hexadecimal floating-point literal.
+  if (Token.getLength() > 2 && Begin[0] == '0' && std::toupper(Begin[1]) == 'X')
+    return std::none_of(Begin + 2, End, [](char C) {
+      return C == '.' || std::toupper(C) == 'P';
+    });
+
+  // Not a decimal floating-point literal or complex literal.
+  return std::none_of(Begin, End, [](char C) {
+    return C == '.' || std::toupper(C) == 'E' || std::toupper(C) == 'I';
+  });
+}
+
+bool IntegralLiteralExpressionMatcher::advance() {
+  ++Current;
+  return Current != End;
+}
+
+bool IntegralLiteralExpressionMatcher::consume(tok::TokenKind Kind) {
+  if (Current->is(Kind)) {
+    ++Current;
+    return true;
+  }
+
+  return false;
+}
+
+bool IntegralLiteralExpressionMatcher::nonTerminalChainedExpr(
+    bool (IntegralLiteralExpressionMatcher::*NonTerminal)(),
+    const std::function<bool(Token)> &IsKind) {
+  if (!(this->*NonTerminal)())
+    return false;
+  if (Current == End)
+    return true;
+
+  while (Current != End) {
+    if (!IsKind(*Current))
+      break;
+
+    if (!advance())
+      return false;
+
+    if (!(this->*NonTerminal)())
+      return false;
+  }
+
+  return true;
+}
+
+// Advance over unary operators.
+bool IntegralLiteralExpressionMatcher::unaryOperator() {
+  if (Current->isOneOf(tok::TokenKind::minus, tok::TokenKind::plus,
+                       tok::TokenKind::tilde, tok::TokenKind::exclaim)) {
+    return advance();
+  }
+
+  return true;
+}
+
+bool IntegralLiteralExpressionMatcher::unaryExpr() {
+  if (!unaryOperator())
+    return false;
+
+  if (consume(tok::TokenKind::l_paren)) {
+    if (Current == End)
+      return false;
+
+    if (!expr())
+      return false;
+
+    if (Current == End)
+      return false;
+
+    return consume(tok::TokenKind::r_paren);
+  }
+
+  if (!Current->isLiteral() || isStringLiteral(Current->getKind()) ||
+      !isIntegralConstant(*Current)) {
+    return false;
+  }
+  ++Current;
+  return true;
+}
+
+bool IntegralLiteralExpressionMatcher::multiplicativeExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::star, tok::TokenKind::slash,
+                                tok::TokenKind::percent>(
+      &IntegralLiteralExpressionMatcher::unaryExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::additiveExpr() {
+  return nonTerminalChainedExpr<tok::plus, tok::minus>(
+      &IntegralLiteralExpressionMatcher::multiplicativeExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::shiftExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::lessless,
+                                tok::TokenKind::greatergreater>(
+      &IntegralLiteralExpressionMatcher::additiveExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::compareExpr() {
+  if (!shiftExpr())
+    return false;
+  if (Current == End)
+    return true;
+
+  if (Current->is(tok::TokenKind::spaceship)) {
+    if (!advance())
+      return false;
+
+    if (!shiftExpr())
+      return false;
+  }
+
+  return true;
+}
+
+bool IntegralLiteralExpressionMatcher::relationalExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::less, tok::TokenKind::greater,
+                                tok::TokenKind::lessequal,
+                                tok::TokenKind::greaterequal>(
+      &IntegralLiteralExpressionMatcher::compareExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::equalityExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::equalequal,
+                                tok::TokenKind::exclaimequal>(
+      &IntegralLiteralExpressionMatcher::relationalExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::andExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::amp>(
+      &IntegralLiteralExpressionMatcher::equalityExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::exclusiveOrExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::caret>(
+      &IntegralLiteralExpressionMatcher::andExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::inclusiveOrExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::pipe>(
+      &IntegralLiteralExpressionMatcher::exclusiveOrExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::logicalAndExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::ampamp>(
+      &IntegralLiteralExpressionMatcher::inclusiveOrExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::logicalOrExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::pipepipe>(
+      &IntegralLiteralExpressionMatcher::logicalAndExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::conditionalExpr() {
+  if (!logicalOrExpr())
+    return false;
+  if (Current == End)
+    return true;
+
+  if (Current->is(tok::TokenKind::question)) {
+    if (!advance())
+      return false;
+
+    // A gcc extension allows x ? : y as a synonym for x ? x : y.
+    if (Current->is(tok::TokenKind::colon)) {
+      if (!advance())
+        return false;
+
+      if (!expr())
+        return false;
+
+      return true;
+    }
+
+    if (!expr())
+      return false;
+    if (Current == End)
+      return false;
+
+    if (!Current->is(tok::TokenKind::colon))
+      return false;
+
+    if (!advance())
+      return false;
+
+    if (!expr())
+      return false;
+  }
+  return true;
+}
+
+bool IntegralLiteralExpressionMatcher::commaExpr() {
+  return nonTerminalChainedExpr<tok::TokenKind::comma>(
+      &IntegralLiteralExpressionMatcher::conditionalExpr);
+}
+
+bool IntegralLiteralExpressionMatcher::expr() { return commaExpr(); }
+
+bool IntegralLiteralExpressionMatcher::match() {
+  return expr() && Current == End;
+}
+
+} // namespace modernize
+} // namespace tidy
+} // namespace clang

clang-tools-extra/clang-tidy/modernize/IntegralLiteralExpressionMatcher.h

@@ -0,0 +1,73 @@
+//===--- IntegralLiteralExpressionMatcher.h - clang-tidy ------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_INTEGRAL_LITERAL_EXPRESSION_MATCHER_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_INTEGRAL_LITERAL_EXPRESSION_MATCHER_H
+
+#include <clang/Lex/Token.h>
+#include <llvm/ADT/ArrayRef.h>
+
+namespace clang {
+namespace tidy {
+namespace modernize {
+
+// Parses an array of tokens and returns true if they conform to the rules of
+// C++ for whole expressions involving integral literals.  Follows the operator
+// precedence rules of C++.
+class IntegralLiteralExpressionMatcher {
+public:
+  IntegralLiteralExpressionMatcher(ArrayRef<Token> Tokens)
+      : Current(Tokens.begin()), End(Tokens.end()) {}
+
+  bool match();
+
+private:
+  bool advance();
+  bool consume(tok::TokenKind Kind);
+  bool nonTerminalChainedExpr(
+      bool (IntegralLiteralExpressionMatcher::*NonTerminal)(),
+      const std::function<bool(Token)> &IsKind);
+  template <tok::TokenKind Kind>
+  bool nonTerminalChainedExpr(
+      bool (IntegralLiteralExpressionMatcher::*NonTerminal)()) {
+    return nonTerminalChainedExpr(NonTerminal,
+                                  [](Token Tok) { return Tok.is(Kind); });
+  }
+  template <tok::TokenKind K1, tok::TokenKind K2, tok::TokenKind... Ks>
+  bool nonTerminalChainedExpr(
+      bool (IntegralLiteralExpressionMatcher::*NonTerminal)()) {
+    return nonTerminalChainedExpr(
+        NonTerminal, [](Token Tok) { return Tok.isOneOf(K1, K2, Ks...); });
+  }
+
+  bool unaryOperator();
+  bool unaryExpr();
+  bool multiplicativeExpr();
+  bool additiveExpr();
+  bool shiftExpr();
+  bool compareExpr();
+  bool relationalExpr();
+  bool equalityExpr();
+  bool andExpr();
+  bool exclusiveOrExpr();
+  bool inclusiveOrExpr();
+  bool logicalAndExpr();
+  bool logicalOrExpr();
+  bool conditionalExpr();
+  bool commaExpr();
+  bool expr();
+
+  ArrayRef<Token>::iterator Current;
+  ArrayRef<Token>::iterator End;
+};
+
+} // namespace modernize
+} // namespace tidy
+} // namespace clang
+
+#endif