[clang] d6ccc29 - [clang][bytecode] Take AccessKinds into account in diagnoseNonConstVa… (#204824)

[via cfe-commits]

Author: Timm Baeder
Date: 2026-06-19T16:22:37+02:00
New Revision: d6ccc29cb3a79631818e30f2f523fc6a91718f8a

URL: https://github.com/llvm/llvm-project/commit/d6ccc29cb3a79631818e30f2f523fc6a91718f8a
DIFF: https://github.com/llvm/llvm-project/commit/d6ccc29cb3a79631818e30f2f523fc6a91718f8a.diff

LOG: [clang][bytecode] Take AccessKinds into account in diagnoseNonConstVa… (#204824)

…riable

And diagnose it as a modification and not a read if applicable.

Added: 
    

Modified: 
    clang/lib/AST/ByteCode/Interp.cpp
    clang/test/AST/ByteCode/cxx20.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index 60914a2da111a..b022d71ae1e49 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -97,9 +97,10 @@ static void noteValueLocation(InterpState &S, const Block *B) {
 }
 
 static void diagnoseNonConstVariable(InterpState &S, CodePtr OpPC,
-                                     const ValueDecl *VD);
+                                     const ValueDecl *VD,
+                                     AccessKinds AK = AK_Read);
 static bool diagnoseUnknownDecl(InterpState &S, CodePtr OpPC,
-                                const ValueDecl *D) {
+                                const ValueDecl *D, AccessKinds AK = AK_Read) {
   // This function tries pretty hard to produce a good diagnostic. Just skip
   // that if nobody will see it anyway.
   if (!S.diagnosing())
@@ -129,7 +130,7 @@ static bool diagnoseUnknownDecl(InterpState &S, CodePtr OpPC,
   }
 
   if (!D->getType().isConstQualified()) {
-    diagnoseNonConstVariable(S, OpPC, D);
+    diagnoseNonConstVariable(S, OpPC, D, AK);
   } else if (const auto *VD = dyn_cast<VarDecl>(D)) {
     if (!VD->getAnyInitializer()) {
       diagnoseMissingInitializer(S, OpPC, VD);
@@ -143,8 +144,13 @@ static bool diagnoseUnknownDecl(InterpState &S, CodePtr OpPC,
   return false;
 }
 
+static bool isModification(AccessKinds AK) {
+  return AK == AK_Assign || AK == AK_Increment || AK == AK_Decrement ||
+         AK == AK_Construct || AK == AK_Destroy;
+}
+
 static void diagnoseNonConstVariable(InterpState &S, CodePtr OpPC,
-                                     const ValueDecl *VD) {
+                                     const ValueDecl *VD, AccessKinds AK) {
   if (!S.diagnosing())
     return;
 
@@ -168,8 +174,12 @@ static void diagnoseNonConstVariable(InterpState &S, CodePtr OpPC,
     return;
 
   if (VD->getType()->isIntegralOrEnumerationType()) {
-    S.FFDiag(Loc, diag::note_constexpr_ltor_non_const_int, 1) << VD;
-    S.Note(VD->getLocation(), diag::note_declared_at);
+    if (isModification(AK)) {
+      S.FFDiag(Loc, diag::note_constexpr_modify_global);
+    } else {
+      S.FFDiag(Loc, diag::note_constexpr_ltor_non_const_int, 1) << VD;
+      S.Note(VD->getLocation(), diag::note_declared_at);
+    }
     return;
   }
 
@@ -1266,7 +1276,7 @@ bool CheckDummy(InterpState &S, CodePtr OpPC, const Block *B, AccessKinds AK) {
     return false;
 
   if (AK == AK_Read || AK == AK_Increment || AK == AK_Decrement)
-    return diagnoseUnknownDecl(S, OpPC, D);
+    return diagnoseUnknownDecl(S, OpPC, D, AK);
 
   if (AK == AK_Destroy || S.getLangOpts().CPlusPlus14) {
     const SourceInfo &E = S.Current->getSource(OpPC);

diff  --git a/clang/test/AST/ByteCode/cxx20.cpp b/clang/test/AST/ByteCode/cxx20.cpp
index a6409d4a2c268..7ff70076ee6e4 100644
--- a/clang/test/AST/ByteCode/cxx20.cpp
+++ b/clang/test/AST/ByteCode/cxx20.cpp
@@ -1,6 +1,11 @@
 // RUN: %clang_cc1 -fcxx-exceptions -std=c++20 -verify=both,expected -fcxx-exceptions %s -DNEW_INTERP -fexperimental-new-constant-interpreter
 // RUN: %clang_cc1 -fcxx-exceptions -std=c++20 -verify=both,ref      -fcxx-exceptions %s
 
+
+int x;
+static_assert(++x, "test"); // both-error {{not an integral constant expression}} \
+                            // both-note {{cannot modify an object that is visible outside that expression}}
+
 void test_alignas_operand() {
   alignas(8) char dummy;
   static_assert(__alignof(dummy) == 8);