[PATCH] D25777: [Sema][TreeTransform] Re-create DesignatedInitExpr when it has a field designator with a valid FieldDecl

[Alex Lorenz via cfe-commits]

arphaman created this revision.
arphaman added reviewers: rjmccall, manmanren.
arphaman added a subscriber: cfe-commits.
arphaman set the repository for this revision to rL LLVM.

This patch fixes an invalid `Winitializer-overrides` warning that's shown for a piece of code like this:

  template <typename T> struct Foo {
    struct SubFoo {
      int bar1;
      int bar2;
    };
  
    static void Test() { 
     SubFoo sf = {.bar1 = 10, 
     // Incorrect "initializer overrides prior initialization" warning shown on the line below when instantiating Foo<bool>
                           .bar2 = 20}; 
    }
  };
  
  void foo() {
    Foo<int>::Test();
    Foo<bool>::Test();
  }

The invalid warning is shown because in the second instantiation of `Foo<T>::Test` the `DesignatedInitExpr` that corresponds to the initializer for `sf` has a field designator with a pointer to the `FieldDecl` from the first instantiation of `Foo<T>::SubFoo`, which is incorrect in the context of the second instantiation. This means that `InitListChecker::CheckDesignatedInitializer` isn't able to find the correct `FieldIndex` for the correct field in the initialized record, leading to an incorrect warning.

This patch fixes this bug by ensuring that a `DesignatedInitExpr` is re-created by the tree-transformer when it has a field designator with a `FieldDecl` that has been already been set. This means that in the example above the `DesignatedInitExpr` won't be re-created by the tree-transformer in the first instantiation, but it will be re-created in the second instantiation, thus ensuring that the second instantiation doesn't have the incorrect `FieldDecl` pointers.


Repository:
  rL LLVM

https://reviews.llvm.org/D25777

Files:
  lib/Sema/TreeTransform.h
  test/SemaCXX/designated-initializers.cpp


Index: test/SemaCXX/designated-initializers.cpp
===================================================================
--- /dev/null
+++ test/SemaCXX/designated-initializers.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify -Winitializer-overrides %s
+
+template <typename T> struct Foo {
+  struct SubFoo {
+    int bar1;
+    int bar2;
+  };
+
+  static void Test() { SubFoo sf = {.bar1 = 10, .bar2 = 20}; } // Expected no warning
+};
+
+void foo() {
+  Foo<int>::Test();
+  Foo<bool>::Test();
+  Foo<float>::Test();
+}
+
+template <typename T> struct Bar {
+  struct SubFoo {
+    int bar1;
+    int bar2;
+  };
+
+  static void Test() { SubFoo sf = {.bar1 = 10,    // expected-note 2 {{previous initialization is here}}
+                                    .bar1 = 20}; } // expected-warning 2 {{initializer overrides prior initialization of this subobject}}
+};
+
+void bar() {
+  Bar<int>::Test();  // expected-note {{in instantiation of member function 'Bar<int>::Test' requested here}}
+  Bar<bool>::Test(); // expected-note {{in instantiation of member function 'Bar<bool>::Test' requested here}}
+}
Index: lib/Sema/TreeTransform.h
===================================================================
--- lib/Sema/TreeTransform.h
+++ lib/Sema/TreeTransform.h
@@ -8923,6 +8923,8 @@
       Desig.AddDesignator(Designator::getField(D.getFieldName(),
                                                D.getDotLoc(),
                                                D.getFieldLoc()));
+      if (D.getField())
+        ExprChanged = true;
       continue;
     }
 


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