BridgeJS: Fix unused result warnings

Author: kateinoigakukun

Plugins/BridgeJS/Sources/BridgeJSCore/ImportTS.swift

@@ -178,13 +178,19 @@ public struct ImportTS {
                 rightParen: .rightParenToken()
             )
 
-            if returnType == .void {
-                body.append(CodeBlockItemSyntax(item: .stmt(StmtSyntax(ExpressionStmtSyntax(expression: callExpr)))))
-            } else if returnType.usesSideChannelForOptionalReturn() {
-                // Side channel returns don't need "let ret ="
-                body.append(CodeBlockItemSyntax(item: .stmt(StmtSyntax(ExpressionStmtSyntax(expression: callExpr)))))
+            let needsRetBinding: Bool
+            let liftingInfo = try returnType.liftingReturnInfo(context: context)
+            if liftingInfo.valueToLift == nil || returnType.usesSideChannelForOptionalReturn() {
+                // Void and side-channel returns don't need "let ret ="
+                needsRetBinding = false
             } else {
+                needsRetBinding = true
+            }
+
+            if needsRetBinding {
                 body.append("let ret = \(raw: callExpr)")
+            } else {
+                body.append(CodeBlockItemSyntax(item: .stmt(StmtSyntax(ExpressionStmtSyntax(expression: callExpr)))))
             }
 
             // Add exception check for ImportTS context

Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSCodegenTests/JSValue.swift

@@ -141,7 +141,7 @@ fileprivate func bjs_jsEchoJSValue(_ valueKind: Int32, _ valuePayload1: Int32, _
 
 func _$jsEchoJSValue(_ value: JSValue) throws(JSException) -> JSValue {
     let (valueKind, valuePayload1, valuePayload2) = value.bridgeJSLowerParameter()
-    let ret = bjs_jsEchoJSValue(valueKind, valuePayload1, valuePayload2)
+    bjs_jsEchoJSValue(valueKind, valuePayload1, valuePayload2)
     if let error = _swift_js_take_exception() {
         throw error
     }

Tests/BridgeJSRuntimeTests/Generated/BridgeJS.swift

@@ -7959,7 +7959,7 @@ fileprivate func bjs_globalObject1_get() -> Void {
 #endif
 
 func _$globalObject1_get() throws(JSException) -> JSValue {
-    let ret = bjs_globalObject1_get()
+    bjs_globalObject1_get()
     if let error = _swift_js_take_exception() {
         throw error
     }
@@ -8083,7 +8083,7 @@ fileprivate func bjs_jsRoundTripJSValue(_ vKind: Int32, _ vPayload1: Int32, _ vP
 
 func _$jsRoundTripJSValue(_ v: JSValue) throws(JSException) -> JSValue {
     let (vKind, vPayload1, vPayload2) = v.bridgeJSLowerParameter()
-    let ret = bjs_jsRoundTripJSValue(vKind, vPayload1, vPayload2)
+    bjs_jsRoundTripJSValue(vKind, vPayload1, vPayload2)
     if let error = _swift_js_take_exception() {
         throw error
     }