[PATCH] D123840: [Clang][Sema] Fix invalid redefinition error in if/switch/for statement

[Jun Zhang via Phabricator via cfe-commits]

junaire created this revision.
junaire added reviewers: aaron.ballman, rsmith, erichkeane, dblaikie, rjmccall.
Herald added a project: All.
junaire requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Because lambda will create its own scope, so we shouldn't consider variables
defined with the same name as redefinition error, if the new one is in a
lambda.

After this patch, clang is supposed to accept code below:

void foo() {

  for (int x = [] { int x = 0; return x; }(); ;) ;

}

Fixes https://github.com/llvm/llvm-project/issues/54913


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D123840

Files:
  clang/lib/Sema/IdentifierResolver.cpp
  clang/test/SemaCXX/cxx1z-init-statement.cpp


Index: clang/test/SemaCXX/cxx1z-init-statement.cpp
===================================================================
--- clang/test/SemaCXX/cxx1z-init-statement.cpp
+++ clang/test/SemaCXX/cxx1z-init-statement.cpp
@@ -90,3 +90,18 @@
   static_assert(constexpr_switch_init(-2) == 0, "");
   static_assert(constexpr_switch_init(-5) == -1, "");
 }
+
+int test_lambda_init() {
+  if (int x = []() {int x = 42; return x; }(); x) {
+  };
+
+  switch (int y = []() {int y = 42; return y; }(); y) {
+  case 42:
+    return 1;
+  }
+
+  for (int x = [] { int x = 0; return x; }();;)
+    ;
+
+  return 0;
+}
Index: clang/lib/Sema/IdentifierResolver.cpp
===================================================================
--- clang/lib/Sema/IdentifierResolver.cpp
+++ clang/lib/Sema/IdentifierResolver.cpp
@@ -121,7 +121,10 @@
       // of the controlled statement.
       //
       assert(S->getParent() && "No TUScope?");
-      if (S->getParent()->getFlags() & Scope::ControlScope) {
+      // If the current decl is in a lambda, we shouldn't consider this is a
+      // redefinition as lambda has its own scope.
+      if (S->getParent()->getFlags() & Scope::ControlScope &&
+          !S->isFunctionScope()) {
         S = S->getParent();
         if (S->isDeclScope(D))
           return true;


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