Derive Clone when all fields are references

Author: lucic71

cpp2rust/converter/converter_lib.cpp

@@ -352,6 +352,15 @@ bool HasDefaultedCopyConstructor(const clang::RecordDecl *decl) {
   return !cxx->defaultedCopyConstructorIsDeleted();
 }
 
+bool RecordHasOnlyReferenceFields(const clang::RecordDecl *decl) {
+  for (auto *field : decl->fields()) {
+    if (!field->getType()->isReferenceType()) {
+      return false;
+    }
+  }
+  return true;
+}
+
 bool HasDefaultedCopyAssignment(const clang::RecordDecl *decl) {
   auto *cxx = clang::dyn_cast<clang::CXXRecordDecl>(decl);
   if (!cxx) {

cpp2rust/converter/converter_lib.h

@@ -87,6 +87,8 @@ bool HasCallableCopyConstructor(const clang::RecordDecl *decl);
 
 bool HasDefaultedCopyConstructor(const clang::RecordDecl *decl);
 
+bool RecordHasOnlyReferenceFields(const clang::RecordDecl *decl);
+
 bool HasDefaultedCopyAssignment(const clang::RecordDecl *decl);
 
 bool IsRValueConvertingConstructor(const clang::CXXConstructorDecl *ctor);

cpp2rust/converter/models/converter_refcount.cpp

@@ -480,6 +480,9 @@ void ConverterRefCount::AddCloneTrait(const clang::RecordDecl *decl) {
     return;
   }
 
+  if (HasDefaultedCopyConstructor(decl) && RecordHasOnlyReferenceFields(decl)) {
+    return;
+  }
   auto *cxx = clang::dyn_cast<clang::CXXRecordDecl>(decl);
   if (!cxx) {
     StrCat(keyword::kImpl, "Clone for", record_name);
@@ -2115,6 +2118,10 @@ ConverterRefCount::GetStructAttributes(const clang::RecordDecl *decl) {
     return attrs;
   }
 
+  if (HasDefaultedCopyConstructor(decl) && RecordHasOnlyReferenceFields(decl)) {
+    attrs.emplace_back("Clone");
+  }
+
   if (RecordDerivesDefault(decl)) {
     attrs.emplace_back("Default");
   }

tests/ub/out/refcount/ctor_ref_member.rs

@@ -6,7 +6,7 @@ use std::io::prelude::*;
 use std::io::{Read, Seek, Write};
 use std::os::fd::AsFd;
 use std::rc::{Rc, Weak};
-#[derive(Default)]
+#[derive(Clone, Default)]
 pub struct S {
     pub r: Ptr<i32>,
 }
@@ -17,15 +17,6 @@ impl S {
         Rc::try_unwrap(__this).ok().unwrap().into_inner()
     }
 }
-impl Clone for S {
-    fn clone(&self) -> Self {
-        let __this: Value<S> = Rc::new(RefCell::new(Self {
-            r: (self.r).clone(),
-        }));
-        let this: Ptr<S> = __this.as_pointer();
-        Rc::try_unwrap(__this).ok().unwrap().into_inner()
-    }
-}
 impl ByteRepr for S {}
 pub fn main() {
     __cpp2rust_init_globals();

tests/ub/out/refcount/ub6.rs

@@ -6,21 +6,11 @@ use std::io::prelude::*;
 use std::io::{Read, Seek, Write};
 use std::os::fd::AsFd;
 use std::rc::{Rc, Weak};
-#[derive(Default)]
+#[derive(Clone, Default)]
 pub struct Pair {
     pub x1: Ptr<i32>,
     pub x2: Ptr<i32>,
 }
-impl Clone for Pair {
-    fn clone(&self) -> Self {
-        let __this: Value<Pair> = Rc::new(RefCell::new(Self {
-            x1: (self.x1).clone(),
-            x2: (self.x2).clone(),
-        }));
-        let this: Ptr<Pair> = __this.as_pointer();
-        Rc::try_unwrap(__this).ok().unwrap().into_inner()
-    }
-}
 impl ByteRepr for Pair {}
 pub fn mkPair_0(x1: Ptr<i32>, x2: Ptr<i32>) -> Pair {
     return Pair {

tests/unit/clone_vs_move.cpp

@@ -16,6 +16,11 @@ struct Foo {
   Bar bar;
 };
 
+struct Refs {
+  int &a;
+  int &b;
+};
+
 int main() {
   int x1 = 1;
   int x2 = x1;
@@ -182,5 +187,15 @@ int main() {
     assert(v2[i] == i + 1);
   }
 
+  int ra = 1, rb = 2;
+  Refs r1{ra, rb};
+  Refs r2 = r1;
+  r2.a = 10;
+  ++r2.b;
+  assert(ra == 10);
+  assert(rb == 3);
+  assert(r1.a == 10);
+  assert(r1.b == 3);
+
   return 0;
 }

tests/unit/out/refcount/clone_vs_move.rs

@@ -69,6 +69,12 @@ impl Default for Foo {
     }
 }
 impl ByteRepr for Foo {}
+#[derive(Clone, Default)]
+pub struct Refs {
+    pub a: Ptr<i32>,
+    pub b: Ptr<i32>,
+}
+impl ByteRepr for Refs {}
 pub fn main() {
     __cpp2rust_init_globals();
     std::process::exit(main_0());
@@ -507,6 +513,19 @@ fn main_0() -> i32 {
         );
         (*i.borrow_mut()).prefix_inc();
     }
+    let ra: Value<i32> = Rc::new(RefCell::new(1));
+    let rb: Value<i32> = Rc::new(RefCell::new(2));
+    let r1: Value<Refs> = Rc::new(RefCell::new(Refs {
+        a: ra.as_pointer(),
+        b: rb.as_pointer(),
+    }));
+    let r2: Value<Refs> = Rc::new(RefCell::new((*r1.borrow()).clone()));
+    (*r2.borrow()).a.write(10);
+    (*r2.borrow()).b.with_mut(|__v| __v.prefix_inc());
+    assert!(((*ra.borrow()) == 10));
+    assert!(((*rb.borrow()) == 3));
+    assert!((((*r1.borrow()).a.read()) == 10));
+    assert!((((*r1.borrow()).b.read()) == 3));
     return 0;
 }
 pub fn __cpp2rust_init_globals() {}

tests/unit/out/refcount/complex_function.rs

@@ -43,19 +43,10 @@ impl ByteRepr for X1 {
         }
     }
 }
-#[derive(Default)]
+#[derive(Clone, Default)]
 pub struct X2 {
     pub v: Ptr<X1>,
 }
-impl Clone for X2 {
-    fn clone(&self) -> Self {
-        let __this: Value<X2> = Rc::new(RefCell::new(Self {
-            v: (self.v).clone(),
-        }));
-        let this: Ptr<X2> = __this.as_pointer();
-        Rc::try_unwrap(__this).ok().unwrap().into_inner()
-    }
-}
 impl ByteRepr for X2 {}
 #[derive(Default)]
 pub struct X3 {

tests/unit/out/refcount/destructor.rs

@@ -9,15 +9,8 @@ use std::rc::{Rc, Weak};
 thread_local!(
     pub static global_0: Value<i32> = Rc::new(RefCell::new(0));
 );
-#[derive(Default)]
+#[derive(Clone, Default)]
 pub struct S {}
-impl Clone for S {
-    fn clone(&self) -> Self {
-        let __this: Value<S> = Rc::new(RefCell::new(Self {}));
-        let this: Ptr<S> = __this.as_pointer();
-        Rc::try_unwrap(__this).ok().unwrap().into_inner()
-    }
-}
 impl ByteRepr for S {
     fn byte_size() -> usize {
         1

tests/unit/out/refcount/function_overloading.rs

@@ -36,15 +36,8 @@ pub fn foo_3(x: Ptr<i32>, y: Ptr<i32>, z: Ptr<i32>) -> i32 {
 pub fn bar_4(x: Ptr<i32>) -> i32 {
     return (x.read());
 }
-#[derive(Default)]
+#[derive(Clone, Default)]
 pub struct Foo {}
-impl Clone for Foo {
-    fn clone(&self) -> Self {
-        let __this: Value<Foo> = Rc::new(RefCell::new(Self {}));
-        let this: Ptr<Foo> = __this.as_pointer();
-        Rc::try_unwrap(__this).ok().unwrap().into_inner()
-    }
-}
 impl ByteRepr for Foo {
     fn byte_size() -> usize {
         1