Kotlin result (#728)

* kotlin - uses results

* kotlin-result - gen example

* kotlin-result - fix example

* kotlin-result - clippy and tests

* kotlin-result - remove Res

example/kotlin/somelib/src/jmh/kotlin/dev/diplomattest/somelib/ICU4XFixedDecimalFormatter.kt

@@ -8,35 +8,35 @@ import org.openjdk.jmh.infra.Blackhole;
 
 @State(Scope.Benchmark)
 internal open class ICU4XFixedDecimalFormatterBench {
-    private val locale = ICU4XLocale.new_("en")
-    private val provider = ICU4XDataProvider.newStatic()
-    private val options = ICU4XFixedDecimalFormatterOptions.default_()
-    private val formatter = ICU4XFixedDecimalFormatter.tryNew(locale, provider, options).wrapErrAndThrow()
-    private val decimal = ICU4XFixedDecimal.new_(123)
+    private val locale = Locale.new_("en")
+    private val provider = DataProvider.newStatic()
+    private val options = FixedDecimalFormatterOptions.default_()
+    private val formatter = FixedDecimalFormatter.tryNew(locale, provider, options).getOrThrow()
+    private val decimal = FixedDecimal.new_(123)
 
     @Benchmark
     fun benchLocale(bh: Blackhole) {
-        bh.consume(ICU4XLocale.new_("en"))
+        bh.consume(Locale.new_("en"))
     }
 
     @Benchmark
     fun benchProvider(bh: Blackhole) {
-        bh.consume(ICU4XDataProvider.newStatic())
+        bh.consume(DataProvider.newStatic())
     }
 
     @Benchmark
     fun benchOptions(bh: Blackhole) {
-        bh.consume(ICU4XFixedDecimalFormatterOptions.default_())
+        bh.consume(FixedDecimalFormatterOptions.default_())
     }
 
     @Benchmark
     fun benchDecimal(bh: Blackhole) {
-        bh.consume(ICU4XFixedDecimal.new_(123))
+        bh.consume(FixedDecimal.new_(123))
     }
 
     @Benchmark
     fun benchFormatter(bh: Blackhole) {
-        bh.consume(ICU4XFixedDecimalFormatter.tryNew(locale, provider, options).wrapErrAndThrow())
+        bh.consume(FixedDecimalFormatter.tryNew(locale, provider, options).getOrThrow())
     }
 
     @Benchmark

example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/DataProvider.kt

@@ -46,13 +46,13 @@ class DataProvider internal constructor (
 
         /** This exists as a regression test for https://github.com/rust-diplomat/diplomat/issues/155
         */
-        fun returnsResult(): Res<Unit, Unit> {
+        fun returnsResult(): Result<Unit> {
 
             val returnVal = lib.icu4x_DataProvider_returns_result_mv1();
             if (returnVal.isOk == 1.toByte()) {
                 return Unit.ok()
             } else {
-                return Err(Unit)
+                return Unit.err()
             }
         }
     }

example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/FixedDecimal.kt

@@ -58,15 +58,15 @@ class FixedDecimal internal constructor (
     *
     *See the [Rust documentation for `write_to`](https://docs.rs/fixed_decimal/latest/fixed_decimal/struct.FixedDecimal.html#method.write_to) for more information.
     */
-    fun toString_(): Res<String, Unit> {
+    fun toString_(): Result<String> {
         val write = DW.lib.diplomat_buffer_write_create(0)
         val returnVal = lib.icu4x_FixedDecimal_to_string_mv1(handle, write);
         if (returnVal.isOk == 1.toByte()) {
 
             val returnString = DW.writeToString(write)
             return returnString.ok()
         } else {
-            return Err(Unit)
+            return Unit.err()
         }
     }
 

example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/FixedDecimalFormatter.kt

@@ -36,7 +36,7 @@ class FixedDecimalFormatter internal constructor (
         *
         *See the [Rust documentation for `try_new`](https://docs.rs/icu/latest/icu/decimal/struct.FixedDecimalFormatter.html#method.try_new) for more information.
         */
-        fun tryNew(locale: Locale, provider: DataProvider, options: FixedDecimalFormatterOptions): Res<FixedDecimalFormatter, Unit> {
+        fun tryNew(locale: Locale, provider: DataProvider, options: FixedDecimalFormatterOptions): Result<FixedDecimalFormatter> {
 
             val returnVal = lib.icu4x_FixedDecimalFormatter_try_new_mv1(locale.handle, provider.handle, options.nativeStruct);
             if (returnVal.isOk == 1.toByte()) {
@@ -46,7 +46,7 @@ class FixedDecimalFormatter internal constructor (
                 CLEANER.register(returnOpaque, FixedDecimalFormatter.FixedDecimalFormatterCleaner(handle, FixedDecimalFormatter.lib));
                 return returnOpaque.ok()
             } else {
-                return Err(Unit)
+                return Unit.err()
             }
         }
     }

example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/Lib.kt

@@ -320,31 +320,13 @@ class Slice: Structure(), Structure.ByValue {
     }
 }
 
-sealed interface Res<T, E>
-class Ok<T, E>(val inner: T) : Res<T, E>
-class Err<T, E>(val inner: E) : Res<T, E>
 
-
-fun <T> Res<T, Throwable>.reThrow(): T {
-    return when (this) {
-        is Ok -> this.inner
-        is Err -> throw this.inner
-    }
-}
-
-fun <T, E> Res<T, E>.wrapErrAndThrow(): T {
-    return when (this) {
-        is Ok -> this.inner
-        is Err -> throw RuntimeException("Received error ${this.inner}")
-    }
-}
-
-fun <T, E> T.ok(): Res<T, E> {
-    return Ok(this)
+internal fun <T> T.ok(): Result<T> {
+    return Result.success(this)
 }
 
-fun <T, E> E.err(): Res<T, E> {
-    return Err(this)
+internal fun <T, E> E.err(): Result<T> {
+    return Result.failure(RuntimeException("Received error $this"))
 }
 
 internal class ResultPointerUnitUnion: Union() {

example/kotlin/somelib/src/test/kotlin/dev/diplomattest/somelib/ICU4XFixedDecimalFormatterTest.kt

@@ -9,7 +9,7 @@ class ICU4XFixedDecimalFormatterTest {
         val locale = Locale.new_("en")
         val provider = DataProvider.newStatic()
         val options = FixedDecimalFormatterOptions.default_()
-        val formatter = FixedDecimalFormatter.tryNew(locale, provider, options).wrapErrAndThrow()
+        val formatter = FixedDecimalFormatter.tryNew(locale, provider, options).getOrThrow()
         val decimal: FixedDecimal = FixedDecimal.new_(123)
         val formatted = formatter.formatWrite(decimal)
         assertEquals(formatted, "123")

tool/src/kotlin/mod.rs

@@ -273,13 +273,9 @@ impl<'a, 'cx> TyGenContext<'a, 'cx> {
     fn gen_return_type_name(&self, result_ty: &ReturnType) -> Cow<'cx, str> {
         match *result_ty {
             ReturnType::Infallible(ref success) => self.gen_infallible_return_type_name(success),
-            ReturnType::Fallible(ref ok, ref err) => {
+            ReturnType::Fallible(ref ok, _) => {
                 let ok_type = self.gen_infallible_return_type_name(ok);
-                let err_type = err
-                    .as_ref()
-                    .map(|err| self.gen_type_name(err, None))
-                    .unwrap_or_else(|| "Unit".into());
-                format!("Res<{ok_type}, {err_type}>").into()
+                format!("Result<{ok_type}>").into()
             }
             ReturnType::Nullable(ref success) => self
                 .formatter
@@ -864,7 +860,7 @@ val intermediateOption = {val_name}.option() ?: return null
                             use_finalizers_not_cleaners,
                         )
                     })
-                    .unwrap_or_else(|| "return Err(Unit)".into());
+                    .unwrap_or_else(|| "return Unit.err()".into());
 
                 #[derive(Template)]
                 #[template(path = "kotlin/ResultReturn.kt.jinja", escape = "none")]