Fix returning Result<Vec<>, ...> from Rust (#218)

Fixes #217 

This supports bridges of the form:
```rust
#[swift_bridge::bridge]
mod ffi {
    extern "Rust" {
        type OpaqueRust;
        fn rust_func_return_result_of_vec_u32() -> Result<Vec<u32>, OpaqueRust>;
        fn rust_func_return_result_of_vec_opaque(
        ) -> Result<Vec<OpaqueRust>, OpaqueRust>;
    }
}

fn rust_func_return_result_of_vec_u32() -> Result<Vec<u32>, OpaqueRust> {
    Ok(vec![0, 1, 2])
}

fn rust_func_return_result_of_vec_opaque(
) -> Result<Vec<OpaqueRust>, OpaqueRust> {
    Ok(vec![
        OpaqueRust::new(...),
        OpaqueRust::new(...),
        OpaqueRust::new(...),
    ])
}
```

SwiftRustIntegrationTestRunner/SwiftRustIntegrationTestRunnerTests/ResultTests.swift

@@ -192,4 +192,21 @@ class ResultTests: XCTestCase {
             }
         }
     }
+
+    /// Verify that we can receive a Result<Vec<>, OpaqueRust> from Rust
+    func testSwiftCallRustResultVecUInt32Rust() throws {
+        let vec = try! rust_func_return_result_of_vec_u32()
+        XCTAssertEqual(vec.len(), 3)
+        for (i, value) in vec.enumerated() {
+            XCTAssertEqual(UInt32(i), value)
+        }
+    }
+
+    func testSwiftCallRustResultVecOpaqueRust() throws {
+        let vec = try! rust_func_return_result_of_vec_opaque()
+        XCTAssertEqual(vec.len(), 3)
+        for (i, value) in vec.enumerated() {
+            XCTAssertEqual(UInt32(i), value.val())
+        }
+    }
 }

crates/swift-bridge-ir/src/bridged_type.rs

@@ -481,6 +481,7 @@ impl BridgeableType for BridgedType {
 
     fn is_passed_via_pointer(&self) -> bool {
         match self {
+            BridgedType::StdLib(StdLibType::Vec(_)) => true,
             BridgedType::StdLib(_) => false,
             BridgedType::Foreign(_) => false,
             BridgedType::Bridgeable(ty) => ty.is_passed_via_pointer(),

crates/swift-integration-tests/src/result.rs

@@ -67,6 +67,12 @@ mod ffi {
         fn same_custom_result_returned_twice_second() -> Result<SameEnum, SameEnum>;
     }
 
+    extern "Rust" {
+        fn rust_func_return_result_of_vec_u32() -> Result<Vec<u32>, ResultTestOpaqueRustType>;
+        fn rust_func_return_result_of_vec_opaque(
+        ) -> Result<Vec<ResultTestOpaqueRustType>, ResultTestOpaqueRustType>;
+    }
+
     extern "Rust" {
         fn rust_func_return_result_tuple_transparent_enum(
             succeed: bool,
@@ -182,6 +188,19 @@ fn same_custom_result_returned_twice_second() -> Result<ffi::SameEnum, ffi::Same
     todo!()
 }
 
+fn rust_func_return_result_of_vec_u32() -> Result<Vec<u32>, ResultTestOpaqueRustType> {
+    Ok(vec![0, 1, 2])
+}
+
+fn rust_func_return_result_of_vec_opaque(
+) -> Result<Vec<ResultTestOpaqueRustType>, ResultTestOpaqueRustType> {
+    Ok(vec![
+        ResultTestOpaqueRustType::new(0),
+        ResultTestOpaqueRustType::new(1),
+        ResultTestOpaqueRustType::new(2),
+    ])
+}
+
 fn rust_func_return_result_tuple_transparent_enum(
     succeed: bool,
 ) -> Result<(i32, ResultTestOpaqueRustType, String), ffi::ResultTransparentEnum> {