[clang] [Clang][Interp] Visit `DecompositionDecl` and create a local variable (PR #100400)

[via cfe-commits]

https://github.com/yronglin updated https://github.com/llvm/llvm-project/pull/100400

>From 6ede7586fc4602ab15be59c58fe5f7181ffaca16 Mon Sep 17 00:00:00 2001
From: yronglin <yronglin777 at gmail.com>
Date: Wed, 24 Jul 2024 23:12:27 +0800
Subject: [PATCH 1/2] [Clang][Interp] Fix handling of DecompositionDecl

Signed-off-by: yronglin <yronglin777 at gmail.com>
---
 clang/lib/AST/Interp/Compiler.cpp          | 13 +++++++++++--
 clang/test/SemaCXX/cxx1z-decomposition.cpp |  1 +
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/clang/lib/AST/Interp/Compiler.cpp b/clang/lib/AST/Interp/Compiler.cpp
index 0fc93c14131e6..6e2f0dbc39dcf 100644
--- a/clang/lib/AST/Interp/Compiler.cpp
+++ b/clang/lib/AST/Interp/Compiler.cpp
@@ -3593,8 +3593,14 @@ VarCreationState Compiler<Emitter>::visitDecl(const VarDecl *VD) {
   if (R.notCreated())
     return R;
 
-  if (R)
-    return true;
+  if (R) {
+    bool Ok = true;
+    if (const auto *DD = dyn_cast<DecompositionDecl>(VD))
+      for (const auto *BD : DD->bindings())
+        if (const auto *HoldingVar = BD->getHoldingVar())
+          Ok &= this->visitDecl(HoldingVar);
+    return Ok;
+  }
 
   if (!R && Context::shouldBeGloballyIndexed(VD)) {
     if (auto GlobalIndex = P.getGlobal(VD)) {
@@ -5234,6 +5240,9 @@ bool Compiler<Emitter>::visitDeclRef(const ValueDecl *D, const Expr *E) {
           return false;
         };
 
+        if (isa<DecompositionDecl>(VD))
+          return revisit(VD);
+
         // Visit local const variables like normal.
         if ((VD->hasGlobalStorage() || VD->isLocalVarDecl() ||
              VD->isStaticDataMember()) &&
diff --git a/clang/test/SemaCXX/cxx1z-decomposition.cpp b/clang/test/SemaCXX/cxx1z-decomposition.cpp
index 305a9ac2ebc24..19c730303625e 100644
--- a/clang/test/SemaCXX/cxx1z-decomposition.cpp
+++ b/clang/test/SemaCXX/cxx1z-decomposition.cpp
@@ -1,5 +1,6 @@
 // RUN: %clang_cc1 -std=c++17 -Wc++20-extensions -verify=expected %s
 // RUN: %clang_cc1 -std=c++20 -Wpre-c++20-compat -verify=expected %s
+// RUN: %clang_cc1 -std=c++20 -Wpre-c++20-compat -fexperimental-new-constant-interpreter -verify=expected %s
 
 void use_from_own_init() {
   auto [a] = a; // expected-error {{binding 'a' cannot appear in the initializer of its own decomposition declaration}}

>From 4a4e2c28d48aa944c28db8865cfa0c76f9ce7e9a Mon Sep 17 00:00:00 2001
From: yronglin <yronglin777 at gmail.com>
Date: Thu, 25 Jul 2024 18:57:05 +0800
Subject: [PATCH 2/2] Address review comments

Signed-off-by: yronglin <yronglin777 at gmail.com>
---
 clang/lib/AST/Interp/Compiler.cpp | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/clang/lib/AST/Interp/Compiler.cpp b/clang/lib/AST/Interp/Compiler.cpp
index 6e2f0dbc39dcf..1de4f3255007e 100644
--- a/clang/lib/AST/Interp/Compiler.cpp
+++ b/clang/lib/AST/Interp/Compiler.cpp
@@ -3593,14 +3593,8 @@ VarCreationState Compiler<Emitter>::visitDecl(const VarDecl *VD) {
   if (R.notCreated())
     return R;
 
-  if (R) {
-    bool Ok = true;
-    if (const auto *DD = dyn_cast<DecompositionDecl>(VD))
-      for (const auto *BD : DD->bindings())
-        if (const auto *HoldingVar = BD->getHoldingVar())
-          Ok &= this->visitDecl(HoldingVar);
-    return Ok;
-  }
+  if (R)
+    return true;
 
   if (!R && Context::shouldBeGloballyIndexed(VD)) {
     if (auto GlobalIndex = P.getGlobal(VD)) {
@@ -5240,6 +5234,7 @@ bool Compiler<Emitter>::visitDeclRef(const ValueDecl *D, const Expr *E) {
           return false;
         };
 
+        // DecompositionDecls are just proxies for us.
         if (isa<DecompositionDecl>(VD))
           return revisit(VD);