wit-bindgen: Prevent conflicting StreamPayload/FuturePayload implementations

WIT 'use' statements are represented as Type::Id(_) Types in this codebase, and get
translated to Rust type aliases in the generated Rust bindings.

Since these aliases may be located at different module paths, creating a StreamPayload
or FuturePayload implementation for more than one of these paths will cause the Rust compiler
to complain about conflicting trait implementations for the same type.

This commit solves this issue by dealiasing payload types of the form Type::Id(_) when generating
a key for the future_payloads and stream_payloads maps. This means each alias set will have at
most one implementation of these traits.

Fixes issue 1432

Author: danielvallance

crates/rust/src/bindgen.rs

@@ -427,13 +427,19 @@ impl Bindgen for FunctionBindgen<'_, '_> {
             Instruction::FutureLift { payload, .. } => {
                 let async_support = self.r#gen.r#gen.async_support_path();
                 let op = &operands[0];
-                let name = payload
-                    .as_ref()
-                    .map(|ty| {
-                        self.r#gen
-                            .type_name_owned_with_id(ty, Identifier::StreamOrFuturePayload)
-                    })
-                    .unwrap_or_else(|| "()".into());
+                let name = match payload {
+                    Some(Type::Id(type_id)) => {
+                        let dealiased_id = dealias(resolve, *type_id);
+                        self.r#gen.type_name_owned_with_id(
+                            &Type::Id(dealiased_id),
+                            Identifier::StreamOrFuturePayload,
+                        )
+                    }
+                    Some(ty) => self
+                        .r#gen
+                        .type_name_owned_with_id(ty, Identifier::StreamOrFuturePayload),
+                    None => "()".into(),
+                };
                 let ordinal = self
                     .r#gen
                     .r#gen
@@ -455,13 +461,19 @@ impl Bindgen for FunctionBindgen<'_, '_> {
             Instruction::StreamLift { payload, .. } => {
                 let async_support = self.r#gen.r#gen.async_support_path();
                 let op = &operands[0];
-                let name = payload
-                    .as_ref()
-                    .map(|ty| {
-                        self.r#gen
-                            .type_name_owned_with_id(ty, Identifier::StreamOrFuturePayload)
-                    })
-                    .unwrap_or_else(|| "()".into());
+                let name = match payload {
+                    Some(Type::Id(type_id)) => {
+                        let dealiased_id = dealias(resolve, *type_id);
+                        self.r#gen.type_name_owned_with_id(
+                            &Type::Id(dealiased_id),
+                            Identifier::StreamOrFuturePayload,
+                        )
+                    }
+                    Some(ty) => self
+                        .r#gen
+                        .type_name_owned_with_id(ty, Identifier::StreamOrFuturePayload),
+                    None => "()".into(),
+                };
                 let ordinal = self
                     .r#gen
                     .r#gen

crates/rust/src/interface.rs

@@ -523,10 +523,13 @@ macro_rules! {macro_name} {{
         func_name: &str,
         payload_type: Option<&Type>,
     ) {
-        let name = if let Some(payload_type) = payload_type {
-            self.type_name_owned(payload_type)
-        } else {
-            "()".into()
+        let name = match payload_type {
+            Some(Type::Id(type_id)) => {
+                let dealiased_id = dealias(self.resolve, *type_id);
+                self.type_name_owned(&Type::Id(dealiased_id))
+            }
+            Some(payload_type) => self.type_name_owned(payload_type),
+            None => "()".into(),
         };
         let map = match payload_for {
             PayloadFor::Future => &mut self.r#gen.future_payloads,

crates/test/src/cpp.rs

@@ -49,6 +49,8 @@ impl LanguageMethods for Cpp {
             "async-trait-function.wit"
             | "error-context.wit"
             | "futures.wit"
+            | "import-export-future.wit"
+            | "import-export-stream.wit"
             | "resources-with-futures.wit"
             | "resources-with-streams.wit"
             | "streams.wit"

crates/test/src/csharp.rs

@@ -48,6 +48,7 @@ impl LanguageMethods for Csharp {
                 | "error-context.wit"
                 | "resource-fallible-constructor.wit"
                 | "async-resource-func.wit"
+                | "import-export-stream.wit"
         )
     }
 

tests/codegen/import-export-future.wit

@@ -0,0 +1,19 @@
+//@ async = true
+
+package a:b;
+
+world w {
+    import i;
+    export i;
+}
+
+interface i {
+    use t.{r};
+    f: func(p: future<r>);
+}
+
+interface t {
+    record r {
+        x: u32,
+    }
+}

tests/codegen/import-export-stream.wit

@@ -0,0 +1,19 @@
+//@ async = true
+
+package a:b;
+
+world w {
+    import i;
+    export i;
+}
+
+interface i {
+    use t.{r};
+    f: func(p: stream<r>);
+}
+
+interface t {
+    record r {
+        x: u32,
+    }
+}