Add isize conversion for enum values used as subscript (#254)

C allows indexing an array with an enum value

Author: lucic71

cpp2rust/converter/models/converter_refcount.cpp

@@ -2165,7 +2165,7 @@ bool ConverterRefCount::ConvertCXXOperatorCallExpr(
       pending_deref_.set(std::format("({} as {}).offset({})",
                                      ConvertObject(expr->getArg(0)),
                                      ConvertPtrType(expr->getArg(0)->getType()),
-                                     ConvertRValue(expr->getArg(1))),
+                                     ConvertSubscriptIndex(expr->getArg(1))),
                          expr);
       break;
     }
@@ -2185,7 +2185,7 @@ bool ConverterRefCount::ConvertCXXOperatorCallExpr(
       StrCat(std::format("({} as {}).offset({})",
                          ConvertObject(expr->getArg(0)),
                          ConvertPtrType(expr->getArg(0)->getType()),
-                         ConvertRValue(expr->getArg(1))));
+                         ConvertSubscriptIndex(expr->getArg(1))));
 
       if (is_inner_boxed) {
         StrCat(GetPointerDerefSuffix(expr->getType()), ".as_pointer()");
@@ -2220,6 +2220,14 @@ void ConverterRefCount::ConvertFunctionParameters(clang::FunctionDecl *decl) {
   }
 }
 
+std::string ConverterRefCount::ConvertSubscriptIndex(clang::Expr *idx) {
+  auto str = ConvertRValue(idx);
+  if (idx->getType()->isEnumeralType()) {
+    return std::format("({}) as isize", str);
+  }
+  return str;
+}
+
 void ConverterRefCount::ConvertArraySubscript(clang::Expr *base,
                                               clang::Expr *idx,
                                               clang::QualType type) {
@@ -2236,12 +2244,12 @@ void ConverterRefCount::ConvertArraySubscript(clang::Expr *base,
       if (IsStringLiteralExpr(base)) {
         StrCat(std::format("Ptr::from_string_literal({}).offset({})",
                            ToString(base->IgnoreParens()->IgnoreImplicit()),
-                           ConvertRValue(idx)));
+                           ConvertSubscriptIndex(idx)));
       } else {
         StrCat(std::format("({} as {}).offset({})",
                            ToString(base->IgnoreImplicit()),
                            ConvertPtrType(base->IgnoreImplicit()->getType()),
-                           ConvertRValue(idx)));
+                           ConvertSubscriptIndex(idx)));
       }
 
       if (is_inner_boxed) {

cpp2rust/converter/models/converter_refcount.h

@@ -244,6 +244,8 @@ class ConverterRefCount final : public Converter {
   std::string ConvertPtrType(clang::QualType type);
   std::string ConvertPointeeType(clang::QualType ptr_type) override;
 
+  std::string ConvertSubscriptIndex(clang::Expr *idx);
+
   std::string GetSafeTypeAsString(clang::QualType qual_type) const;
 
   /// The kind of conversion that should be performed.

tests/unit/enum_int_interop_c.c

@@ -140,5 +140,16 @@ int main() {
   assert(entries[2].color == BLUE);
   assert(entries[2].opt == OPT_C);
 
+  const char *names[] = {"red", "green", "blue"};
+  enum Color idx = GREEN;
+  assert(names[idx][0] == 'g');
+  assert(entries[idx].opt == OPT_A);
+  assert(names[global_tag][0] == 'b');
+
+  const char **pp = &names[idx];
+  assert((*pp)[0] == 'g');
+  struct Entry *pe = &entries[idx];
+  assert(pe->opt == OPT_A);
+
   return 0;
 }

tests/unit/out/refcount/enum_int_interop_c.rs

@@ -319,5 +319,50 @@ fn main_0() -> i32 {
             == ((Option::OPT_C as i32) as u32)) as i32)
             != 0)
     );
+    let names: Value<Box<[Ptr<u8>]>> = Rc::new(RefCell::new(Box::new([
+        Ptr::from_string_literal(b"red"),
+        Ptr::from_string_literal(b"green"),
+        Ptr::from_string_literal(b"blue"),
+    ])));
+    let idx: Value<Color> = Rc::new(RefCell::new(Color::GREEN));
+    assert!(
+        ((((((*names.borrow())[(*idx.borrow()) as usize]
+            .offset((0) as isize)
+            .read()) as i32)
+            == ('g' as i32)) as i32)
+            != 0)
+    );
+    assert!(
+        (((((*(*entries_3.with(Value::clone).borrow())[(*idx.borrow()) as usize]
+            .opt
+            .borrow()) as u32)
+            == ((Option::OPT_A as i32) as u32)) as i32)
+            != 0)
+    );
+    assert!(
+        ((((((*names.borrow())[(*global_tag_2.with(Value::clone).borrow()) as usize]
+            .offset((0) as isize)
+            .read()) as i32)
+            == ('b' as i32)) as i32)
+            != 0)
+    );
+    let pp: Value<Ptr<Ptr<u8>>> = Rc::new(RefCell::new(
+        ((names.as_pointer() as Ptr<Ptr<u8>>).offset((*idx.borrow()) as isize)),
+    ));
+    assert!(
+        (((((((*pp.borrow()).read()).offset((0) as isize).read()) as i32) == ('g' as i32)) as i32)
+            != 0)
+    );
+    let pe: Value<Ptr<Entry>> = Rc::new(RefCell::new(
+        ((entries_3.with(Value::clone).as_pointer() as Ptr<Entry>)
+            .offset((*idx.borrow()) as isize)),
+    ));
+    assert!(
+        ((({
+            let _lhs = ((*(*(*pe.borrow()).upgrade().deref()).opt.borrow()) as u32).clone();
+            _lhs == ((Option::OPT_A as i32) as u32)
+        }) as i32)
+            != 0)
+    );
     return 0;
 }

tests/unit/out/unsafe/enum_int_interop_c.rs

@@ -220,5 +220,26 @@ unsafe fn main_0() -> i32 {
     assert!(
         ((((entries_3[(2) as usize].opt as u32) == ((Option::OPT_C as i32) as u32)) as i32) != 0)
     );
+    let mut names: [*const libc::c_char; 3] = [
+        (c"red".as_ptr().cast_mut()).cast_const(),
+        (c"green".as_ptr().cast_mut()).cast_const(),
+        (c"blue".as_ptr().cast_mut()).cast_const(),
+    ];
+    let mut idx: Color = Color::GREEN;
+    assert!(
+        (((((*names[(idx) as usize].offset((0) as isize)) as i32) == ('g' as i32)) as i32) != 0)
+    );
+    assert!(
+        ((((entries_3[(idx) as usize].opt as u32) == ((Option::OPT_A as i32) as u32)) as i32) != 0)
+    );
+    assert!(
+        (((((*names[(global_tag_2) as usize].offset((0) as isize)) as i32) == ('b' as i32))
+            as i32)
+            != 0)
+    );
+    let mut pp: *mut *const libc::c_char = (&mut names[(idx) as usize] as *mut *const libc::c_char);
+    assert!((((((*(*pp).offset((0) as isize)) as i32) == ('g' as i32)) as i32) != 0));
+    let mut pe: *mut Entry = (&mut entries_3[(idx) as usize] as *mut Entry);
+    assert!((((((*pe).opt as u32) == ((Option::OPT_A as i32) as u32)) as i32) != 0));
     return 0;
 }