allow for flattening of generic parameters

macros/src/lib.rs

@@ -158,7 +158,7 @@ impl DerivedTS {
                     type WithoutGenerics = #generics;
                     fn name() -> String { stringify!(#generics).to_owned() }
                     fn inline() -> String { panic!("{} cannot be inlined", #name) }
-                    fn inline_flattened() -> String { panic!("{} cannot be flattened", #name) }
+                    fn inline_flattened() -> String { stringify!(#generics).to_owned() }
                     fn decl() -> String { panic!("{} cannot be declared", #name) }
                     fn decl_concrete() -> String { panic!("{} cannot be declared", #name) }
                 }

ts-rs/tests/integration/generics_flatten.rs

@@ -0,0 +1,49 @@
+use ts_rs_macros::TS;
+
+// https://github.com/Aleph-Alpha/ts-rs/issues/335
+#[derive(TS)]
+#[ts(export, export_to = "generics/flatten/")]
+struct Item<D> {
+    id: String,
+    #[ts(flatten)]
+    inner: D,
+}
+
+#[derive(TS)]
+#[ts(export, export_to = "generics/flatten/")]
+struct TwoParameters<A, B> {
+    id: String,
+    #[ts(flatten)]
+    a: A,
+    #[ts(flatten)]
+    b: B,
+    ab: (A, B),
+}
+
+#[derive(TS)]
+#[ts(export, export_to = "generics/flatten/")]
+enum Enum<A, B> {
+    A {
+        #[ts(flatten)]
+        a: A,
+    },
+    B {
+        #[ts(flatten)]
+        b: B,
+    },
+    AB(A, B),
+}
+
+#[test]
+fn flattened_generic_parameters() {
+    use ts_rs::TS;
+
+    #[derive(TS)]
+    struct Inner {
+        x: i32,
+    }
+
+    assert_eq!(Item::<()>::decl(), "type Item<D> = { id: string, } & D;");
+    assert_eq!(TwoParameters::<(), ()>::decl(), "type TwoParameters<A, B> = { id: string, ab: [A, B], } & A & B;");
+    assert_eq!(Enum::<(), ()>::decl(), "type Enum<A, B> = { \"A\": A } | { \"B\": B } | { \"AB\": [A, B] };");
+}

ts-rs/tests/integration/main.rs

@@ -15,6 +15,7 @@ mod flatten;
 mod generic_fields;
 mod generic_without_import;
 mod generics;
+mod generics_flatten;
 mod hashmap;
 mod hashset;
 mod imports;