Add value-returning match expressions

internal/lang/coroutines.go

@@ -66,6 +66,15 @@ func expressionUsesCoroutines(expr Expr) bool {
 		}
 	case LambdaExpr:
 		return statementsUseCoroutines(e.Body)
+	case MatchExpr:
+		if expressionUsesCoroutines(e.Value) {
+			return true
+		}
+		for _, matchCase := range e.Cases {
+			if expressionUsesCoroutines(matchCase.Value) {
+				return true
+			}
+		}
 	case SelectorExpr:
 		return expressionUsesCoroutines(e.Receiver)
 	case BinaryExpr: