[clang-tools-extra] [clang] [clang-tidy] Improve performance of misc-const-correctness (PR #72705)

[Congcong Cai via cfe-commits]

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@@ -15,6 +15,76 @@
 namespace clang {
 using namespace ast_matchers;
 
+static bool canResolveToExprImpl(const Expr *Node, const Expr *Target) {
+
+  const auto IgnoreDerivedToBase = [](const Expr *E, auto Matcher) {
+    if (Matcher(E))
+      return true;
+    if (const auto *Cast = dyn_cast<ImplicitCastExpr>(E)) {
+      if ((Cast->getCastKind() == CK_DerivedToBase ||
+           Cast->getCastKind() == CK_UncheckedDerivedToBase) &&
+          Matcher(Cast->getSubExpr()))
+        return true;
+    }
+    return false;
+  };
+
+  const auto EvalCommaExpr = [](const Expr *E, auto Matcher) {
+    const Expr *Result = E;
+    while (const auto *BOComma =
+               dyn_cast_or_null<BinaryOperator>(Result->IgnoreParens())) {
+      if (!BOComma->isCommaOp())
+        break;
+      Result = BOComma->getRHS();
+    }
+
+    return Result != E && Matcher(Result);
+  };
+
+  // The 'ConditionalOperatorM' matches on `<anything> ? <expr> : <expr>`.
+  // This matching must be recursive because `<expr>` can be anything resolving
+  // to the `InnerMatcher`, for example another conditional operator.
+  // The edge-case `BaseClass &b = <cond> ? DerivedVar1 : DerivedVar2;`
+  // is handled, too. The implicit cast happens outside of the conditional.
+  // This is matched by `IgnoreDerivedToBase(canResolveToExpr(InnerMatcher))`
+  // below.
+  const auto ConditionalOperatorM = [Target](const Expr *E, auto Matcher) {
+    if (const auto *OP = dyn_cast<ConditionalOperator>(E)) {
+      if (const auto *TE = OP->getTrueExpr()->IgnoreParens())
+        if (canResolveToExprImpl(TE, Target))
+          return true;
+      if (const auto *FE = OP->getFalseExpr()->IgnoreParens())
+        if (canResolveToExprImpl(FE, Target))
+          return true;
+    }
+    return false;
+  };
+
+  const auto ElvisOperator = [Target](const Expr *E, auto Matcher) {
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HerrCai0907 wrote:

useless arguments `Matcher`

https://github.com/llvm/llvm-project/pull/72705