[clang-tidy] Fix false-positives in misc-static-assert caused by non-constexpr variables

[PiotrZSL]

Summary

Ignore false-positives when referring to non-constexpr variables
in non-unevaluated context (like decltype, sizeof, ...).

Fixes: #24066

[PiotrZSL]

Ping

clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp

 //===--- StaticAssertCheck.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 "StaticAssertCheck.h"
+#include "../utils/Matchers.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Expr.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Casting.h"
auto AssertExprRoot = anyOf(
           hasAnyOperatorName("&&", "=="),
           hasEitherOperand(ignoringImpCasts(stringLiteral().bind("assertMSG"))),
           anyOf(binaryOperator(hasEitherOperand(IsAlwaysFalseWithCast)),
                 anything()))
           .bind("assertExprRoot"),
       IsAlwaysFalse);
   auto NonConstexprFunctionCall =
       callExpr(hasDeclaration(functionDecl(unless(isConstexpr()))));
+  auto NonConstexprVariableReference =
+      declRefExpr(to(varDecl(unless(isConstexpr()))),
+                  unless(hasAncestor(expr(matchers::hasUnevaluatedContext()))),
+                  unless(hasAncestor(typeLoc())));
+
+  auto NonConstexprCode =
+      expr(anyOf(NonConstexprFunctionCall, NonConstexprVariableReference));
   auto AssertCondition =
       expr(
           anyOf(expr(ignoringParenCasts(anyOf(
                     AssertExprRoot, unaryOperator(hasUnaryOperand(
                                         ignoringParenCasts(AssertExprRoot)))))),
                 anything()),
-          unless(findAll(NonConstexprFunctionCall)))
+          unless(NonConstexprCode), unless(hasDescendant(NonConstexprCode)))
           .bind("condition");
   auto Condition =
       anyOf(ignoringParenImpCasts(callExpr(
                 hasDeclaration(functionDecl(hasName("__builtin_expect"))),
                 hasArgument(0, AssertCondition))),
             AssertCondition);
 
   Finder->addMatcher(conditionalOperator(hasCondition(Condition),

clang-tools-extra/docs/ReleaseNotes.rst

 - Improved :doc:`misc-include-cleaner
   <clang-tidy/checks/misc/include-cleaner>` check by adding option
   `DeduplicateFindings` to output one finding per symbol occurrence.
 
 - Improved :doc:`misc-redundant-expression
   <clang-tidy/checks/misc/redundant-expression>` check to ignore
   false-positives in unevaluated context (e.g., ``decltype``).
 
+- Improved :doc:`misc-static-assert
+  <clang-tidy/checks/misc/static-assert>` check to ignore false-positives when
+  referring to non-``constexpr`` variables in non-unevaluated context.
+
 - Improved :doc:`modernize-loop-convert
   <clang-tidy/checks/modernize/loop-convert>` to support for-loops with
   iterators initialized by free functions like ``begin``, ``end``, or ``size``.
 
 - Improved :doc:`performance-faster-string-find
   <clang-tidy/checks/performance/faster-string-find>` check to properly escape
   single quotes.
 

clang-tools-extra/test/clang-tidy/checkers/misc/static-assert.cpp

 #define ZERO_MACRO 0
 
 #define False false
 #define FALSE 0
 
 #define my_macro() assert(0 == 1)
 // CHECK-FIXES: #define my_macro() assert(0 == 1)
 
+namespace PR24066 {
+
+void referenceMember() {
+  struct {
+    int A;
+    int B;
+  } S;
+  assert(&S.B - &S.A == 1);
+}
+
+const int X = 1;
+void referenceVariable() {
+  assert(X > 0);
+}
+
+
+constexpr int Y = 1;
+void referenceConstexprVariable() {
+  assert(Y > 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: found assert() that could be replaced by static_assert() [misc-static-assert]
+  // CHECK-FIXES-CXX11: {{^  }}static_assert(Y > 0, "");
+  // CHECK-FIXES-CXX17: {{^  }}static_assert(Y > 0);
+}
+
+void useInSizeOf() {
+  char a = 0;
+  assert(sizeof(a) == 1U);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: found assert() that could be replaced by static_assert() [misc-static-assert]
+  // CHECK-FIXES-CXX11: {{^  }}static_assert(sizeof(a) == 1U, "");
+  // CHECK-FIXES-CXX17: {{^  }}static_assert(sizeof(a) == 1U);
+}
+
+void useInDecltype() {
+  char a = 0;
+  assert(static_cast<decltype(a)>(256) == 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: found assert() that could be replaced by static_assert() [misc-static-assert]
+  // CHECK-FIXES-CXX11: {{^  }}static_assert(static_cast<decltype(a)>(256) == 0, "");
+  // CHECK-FIXES-CXX17: {{^  }}static_assert(static_cast<decltype(a)>(256) == 0);
+}
+
+}
+
 constexpr bool myfunc(int a, int b) { return a * b == 0; }
 
 typedef __SIZE_TYPE__ size_t;
 extern "C" size_t strlen(const char *s);
 
 class A {
 public:
   bool method() { return true; }