[clang-tidy] Fix crashes on `if consteval` in readability checks

The `readability-braces-around-statements` check tries to look at the
closing parens of the if condition to determine where to insert braces,
however, "consteval if" statements don't have a condition, and always
have braces regardless, so the skip can be checked.

The `readability-simplify-boolean-expr` check looks at the condition
of the if statement to determine what could be simplified, but as
"consteval if" statements do not have a condition that could be
simplified, they can also be skipped here.

There may still be more checks that try to look at the conditions of
`if`s that aren't included here

Fixes https://github.com/llvm/llvm-project/issues/57568

Reviewed By: njames93, aaron.ballman

Differential Revision: https://reviews.llvm.org/D133413

clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp

@@ -131,6 +131,10 @@ void BracesAroundStatementsCheck::check(
       return;
     checkStmt(Result, S->getBody(), StartLoc);
   } else if (const auto *S = Result.Nodes.getNodeAs<IfStmt>("if")) {
+    // "if consteval" always has braces.
+    if (S->isConsteval())
+      return;
+
     SourceLocation StartLoc = findRParenLoc(S, SM, Context);
     if (StartLoc.isInvalid())
       return;

clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp

@@ -354,8 +354,9 @@ public:
   }
 
   bool VisitIfStmt(IfStmt *If) {
-    // Skip any if's that have a condition var or an init statement.
-    if (If->hasInitStorage() || If->hasVarStorage())
+    // Skip any if's that have a condition var or an init statement, or are
+    // "if consteval" statements.
+    if (If->hasInitStorage() || If->hasVarStorage() || If->isConsteval())
       return true;
     /*
      * if (true) ThenStmt(); -> ThenStmt();
@@ -467,7 +468,8 @@ public:
          * if (Cond) return false; return true; -> return !Cond;
          */
         auto *If = cast<IfStmt>(*First);
-        if (!If->hasInitStorage() && !If->hasVarStorage()) {
+        if (!If->hasInitStorage() && !If->hasVarStorage() &&
+            !If->isConsteval()) {
           ExprAndBool ThenReturnBool =
               checkSingleStatement(If->getThen(), parseReturnLiteralBool);
           if (ThenReturnBool &&
@@ -491,7 +493,7 @@ public:
                                     : cast<DefaultStmt>(*First)->getSubStmt();
         auto *SubIf = dyn_cast<IfStmt>(SubStmt);
         if (SubIf && !SubIf->getElse() && !SubIf->hasInitStorage() &&
-            !SubIf->hasVarStorage()) {
+            !SubIf->hasVarStorage() && !SubIf->isConsteval()) {
           ExprAndBool ThenReturnBool =
               checkSingleStatement(SubIf->getThen(), parseReturnLiteralBool);
           if (ThenReturnBool &&

clang-tools-extra/docs/ReleaseNotes.rst

@@ -159,6 +159,11 @@ Changes in existing checks
   <clang-tidy/checks/readability/avoid-const-params-in-decls>` to not
   warn about `const` value parameters of declarations inside macros.
 
+- Fixed crashes in :doc:`readability-braces-around-statements
+  <clang-tidy/checks/readability/braces-around-statements>` and
+  :doc:`readability-simplify-boolean-expr <clang-tidy/checks/readability/simplify-boolean-expr>`
+  when using a C++23 ``if consteval`` statement.
+
 Removed checks
 ^^^^^^^^^^^^^^
 

clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements-consteval-if.cpp

@@ -0,0 +1,31 @@
+// RUN: clang-tidy %s -checks='-*,readability-braces-around-statements' -- -std=c++2b | count 0
+
+constexpr void handle(bool) {}
+
+constexpr void shouldPass() {
+  if consteval {
+    handle(true);
+  } else {
+    handle(false);
+  }
+}
+
+constexpr void shouldPassNegated() {
+  if !consteval {
+    handle(false);
+  } else {
+    handle(true);
+  }
+}
+
+constexpr void shouldPassSimple() {
+  if consteval {
+    handle(true);
+  }
+}
+
+void run() {
+    shouldPass();
+    shouldPassNegated();
+    shouldPassSimple();
+}

clang-tools-extra/test/clang-tidy/checkers/readability/simplify-bool-expr-cxx23.cpp

@@ -0,0 +1,37 @@
+// RUN: clang-tidy %s -checks='-*,readability-simplify-boolean-expr' -- -std=c++2b | count 0
+template <bool Cond>
+constexpr int testIf() {
+  if consteval {
+    if constexpr (Cond) {
+      return 0;
+    } else {
+      return 1;
+    }
+  } else {
+    return 2;
+  }
+}
+
+constexpr bool testCompound() {
+  if consteval {
+    return true;
+  }
+  return false;
+}
+
+constexpr bool testCase(int I) {
+  switch (I) {
+    case 0: {
+      if consteval {
+        return true;
+      }
+      return false;
+    }
+    default: {
+      if consteval {
+        return false;
+      }
+      return true;
+    }
+  }
+}