Fix kotlin unsigned type conversion

feature_tests/src/structs.rs

@@ -142,6 +142,10 @@ pub mod ffi {
                 .collect();
             Box::new(Utf16Wrap(chars))
         }
+
+        pub fn to_unsigned_from_unsigned(&self, input: u16) -> u16 {
+            input
+        }
     }
 
     impl Utf16Wrap {

feature_tests/src/traits.rs

@@ -6,7 +6,7 @@ mod ffi {
         y: i32,
     }
     pub trait TesterTrait {
-        fn test_trait_fn(&self, x: i32) -> i32;
+        fn test_trait_fn(&self, x: u32) -> u32;
         fn test_void_trait_fn(&self);
         fn test_struct_trait_fn(&self, s: TraitTestingStruct) -> i32;
     }
@@ -18,7 +18,7 @@ mod ffi {
     impl TraitWrapper {
         pub fn test_with_trait(t: impl TesterTrait, x: i32) -> i32 {
             t.test_void_trait_fn();
-            t.test_trait_fn(x)
+            t.test_trait_fn(x.try_into().unwrap()).try_into().unwrap()
         }
 
         pub fn test_trait_with_struct(t: impl TesterTrait) -> i32 {

tool/src/kotlin/formatter.rs

@@ -40,7 +40,6 @@ impl<'tcx> KotlinFormatter<'tcx> {
 
     pub fn fmt_primitive_to_native_conversion(&self, name: &str, prim: PrimitiveType) -> String {
         match prim {
-            PrimitiveType::Bool => format!("{name}.toByte()"),
             PrimitiveType::Int(IntType::U8) => format!("{name}.toByte()"),
             PrimitiveType::Int(IntType::U16) => format!("{name}.toShort()"),
             PrimitiveType::Int(IntType::U32) => format!("{name}.toInt()"),
@@ -70,21 +69,55 @@ impl<'tcx> KotlinFormatter<'tcx> {
         "Array<String>"
     }
 
-    pub fn fmt_primitive_as_ffi(&self, prim: PrimitiveType) -> &'static str {
+    pub fn fmt_primitive_as_ffi(
+        &self,
+        prim: PrimitiveType,
+        support_unsigned: bool,
+    ) -> &'static str {
         match prim {
-            PrimitiveType::Bool => "Byte",
+            PrimitiveType::Bool => "Boolean",
             PrimitiveType::Char => "Int",
             PrimitiveType::Int(IntType::I8) => "Byte",
             PrimitiveType::Int(IntType::I16) => "Short",
             PrimitiveType::Int(IntType::I32) => "Int",
             PrimitiveType::Int(IntType::I64) => "Long",
-            PrimitiveType::Int(IntType::U8) => "UByte",
-            PrimitiveType::Int(IntType::U16) => "UShort",
-            PrimitiveType::Int(IntType::U32) => "UInt",
-            PrimitiveType::Int(IntType::U64) => "ULong",
+            PrimitiveType::Int(IntType::U8) => {
+                if support_unsigned {
+                    "UByte"
+                } else {
+                    "Byte"
+                }
+            }
+            PrimitiveType::Int(IntType::U16) => {
+                if support_unsigned {
+                    "UShort"
+                } else {
+                    "Short"
+                }
+            }
+            PrimitiveType::Int(IntType::U32) => {
+                if support_unsigned {
+                    "UInt"
+                } else {
+                    "Int"
+                }
+            }
+            PrimitiveType::Int(IntType::U64) => {
+                if support_unsigned {
+                    "ULong"
+                } else {
+                    "Long"
+                }
+            }
             PrimitiveType::Byte => "Byte",
             PrimitiveType::IntSize(IntSizeType::Isize) => "Long",
-            PrimitiveType::IntSize(IntSizeType::Usize) => "Long",
+            PrimitiveType::IntSize(IntSizeType::Usize) => {
+                if support_unsigned {
+                    "ULong"
+                } else {
+                    "Long"
+                }
+            }
             PrimitiveType::Float(FloatType::F32) => "Float",
             PrimitiveType::Float(FloatType::F64) => "Double",
             PrimitiveType::Int128(_) => panic!("i128 not supported in Kotlin"),
@@ -342,7 +375,7 @@ impl<'tcx> KotlinFormatter<'tcx> {
             PrimitiveType::Int(IntType::U32) => "Int",
             PrimitiveType::Int(IntType::U64) => "Long",
             PrimitiveType::IntSize(_) => "Long",
-            prim => self.fmt_primitive_as_ffi(prim),
+            prim => self.fmt_primitive_as_ffi(prim, false),
         }
     }
 

tool/src/kotlin/mod.rs

@@ -597,11 +597,11 @@ return string{return_type_modifier}"#
                 _ => todo!(),
             },
             Slice::Primitive(Some(_), prim_ty) => {
-                let prim_ty = self.formatter.fmt_primitive_as_ffi(*prim_ty);
+                let prim_ty = self.formatter.fmt_primitive_as_kt(*prim_ty);
                 format!("    return PrimitiveArrayTools.get{prim_ty}Array({val_name}){return_type_modifier}")
             }
             Slice::Primitive(None, prim_ty) => {
-                let prim_ty = self.formatter.fmt_primitive_as_ffi(*prim_ty);
+                let prim_ty = self.formatter.fmt_primitive_as_kt(*prim_ty);
                 let prim_ty_array = format!("{prim_ty}Array");
                 Self::boxed_slice_return(prim_ty_array.as_str(), val_name, return_type_modifier)
             }
@@ -1106,7 +1106,7 @@ returnVal.option() ?: return null
                         .unzip();
                     let (native_output_type, return_modification) = match **output {
                         Some(ref ty) => (
-                            self.gen_native_type_name(ty, None).into(),
+                            self.gen_native_type_name(ty, None, false).into(),
                             match ty {
                                 Type::Enum(..) => ".toNative()",
                                 Type::Struct(..) => ".nativeStruct",
@@ -1286,7 +1286,7 @@ returnVal.option() ?: return null
 
             param_decls.push(format!(
                 "{param_name}: {}",
-                self.gen_native_type_name(&param.ty, additional_name.clone()),
+                self.gen_native_type_name(&param.ty, additional_name.clone(), false),
             ));
         }
         if let ReturnType::Infallible(SuccessType::Write)
@@ -1603,7 +1603,7 @@ returnVal.option() ?: return null
             });
         let (native_output_type, return_modification) = match *method.output {
             Some(ref ty) => (
-                self.gen_native_type_name(ty, None).into(),
+                self.gen_native_type_name(ty, None, true).into(),
                 match ty {
                     Type::Enum(..) => ".toNative()",
                     Type::Struct(..) => ".nativeStruct",
@@ -1827,9 +1827,18 @@ returnVal.option() ?: return null
         &self,
         ty: &Type<P>,
         additional_name: Option<String>,
+        // flag to represent whether the API this type is a part of has support for unsigned types.
+        // Non-trait methods do not, because they are called through the JNA library built in Java
+        // which doesn't support unsigned types.
+        // The true fix is to use JNA `IntegerType` to represent unsigned ints:
+        // TODO: https://github.com/rust-diplomat/diplomat/issues/748
+        support_unsigned: bool,
     ) -> Cow<'cx, str> {
         match *ty {
-            Type::Primitive(prim) => self.formatter.fmt_primitive_as_ffi(prim).into(),
+            Type::Primitive(prim) => self
+                .formatter
+                .fmt_primitive_as_ffi(prim, support_unsigned)
+                .into(),
             Type::Opaque(ref op) => {
                 let optional = if op.is_optional() { "?" } else { "" };
                 format!("Pointer{optional}").into()