Fix the res running variable is not consistent with DiffTests

shared/src/main/scala/mlscript/JSBackend.scala

@@ -594,9 +594,8 @@ class JSTestBackend extends JSBackend {
               ((JSIdent("globalThis").member(sym.runtimeName) := (expr match {
                 case t: JSArrowFn => t.toFuncExpr(S(sym.runtimeName))
                 case t            => t
-              })) ::
-                (resultIdent := JSIdent(sym.runtimeName)) ::
-                Nil)
+              })) :: Nil),
+              sym.runtimeName
             )
           case L(reason) => JSTestBackend.AbortedQuery(reason)
         }
@@ -606,7 +605,9 @@ class JSTestBackend extends JSBackend {
       case term: Term =>
         try {
           val body = translateTerm(term)(scope)
-          JSTestBackend.CodeQuery(scope.tempVars.emit(), (resultIdent := body) :: Nil)
+          val res = JSTestBackend.CodeQuery(scope.tempVars.emit(), (resultIdent := body) :: Nil)
+          scope.refreshRes()
+          res
         } catch {
           case e: UnimplementedError => JSTestBackend.AbortedQuery(e.getMessage())
           case e: Throwable          => throw e
@@ -641,18 +642,19 @@ object JSTestBackend {
   /**
     * The entry generates meaningful code.
     */
-  final case class CodeQuery(prelude: Ls[Str], code: Ls[Str]) extends Query {
+  final case class CodeQuery(prelude: Ls[Str], code: Ls[Str], res: Str) extends Query {
 
   }
 
   object CodeQuery {
-    def apply(decls: Opt[JSLetDecl], stmts: Ls[JSStmt]): CodeQuery =
+    def apply(decls: Opt[JSLetDecl], stmts: Ls[JSStmt], res: Str = "res"): CodeQuery =
       CodeQuery(
         decls match {
           case S(stmt) => stmt.toSourceCode.toLines
           case N       => Nil
         },
-        SourceCode.fromStmts(stmts).toLines
+        SourceCode.fromStmts(stmts).toLines,
+        res
       )
   }
 

shared/src/main/scala/mlscript/codegen/Scope.scala

@@ -7,6 +7,7 @@ import scala.reflect.ClassTag
 import mlscript.{TypeName, Top, Bot, TypeDef, Als, Trt, Cls}
 import mlscript.MethodDef
 import mlscript.Term
+import mlscript.utils.AnyOps
 
 class Scope(name: Str, enclosing: Opt[Scope]) {
   private val lexicalTypeSymbols = scala.collection.mutable.HashMap[Str, TypeSymbol]()
@@ -301,6 +302,10 @@ class Scope(name: Str, enclosing: Opt[Scope]) {
     * Shorthands for deriving function scopes.
     */
   def derive(name: Str, params: Ls[Str]): Scope = Scope(name, params, this)
+
+  def refreshRes(): Unit = {
+    lexicalValueSymbols("res") = ValueSymbol("res", "res")
+  }
 }
 
 object Scope {
@@ -330,6 +335,7 @@ final case class TemporaryVariableEmitter() {
     * Add a new variable name. The name must be a runtime name.
     */
   def +=(name: Str): Unit = names += name
+  def -=(name: Str): Unit = names -= name
 
   /**
     * Emit a `let`-declaration for collected names and clear the collection.

shared/src/test/diff/codegen/Classes.mls

@@ -33,7 +33,6 @@ def Box value = Box { inner = value }
 //│ globalThis.Box1 = function Box1(value) {
 //│   return new Box({ inner: value });
 //│ };
-//│ res = Box1;
 //│ // End of generated code
 //│ Box: 'inner -> Box['inner]
 //│    = [Function: Box1]
@@ -43,10 +42,8 @@ def box1 = Box 1
 def box2 = box1.Map (fun x -> add x 1)
 //│ // Query 1
 //│ globalThis.box1 = Box1(1);
-//│ res = box1;
 //│ // Query 2
 //│ globalThis.box2 = box1.Map((x) => add(x)(1));
-//│ res = box2;
 //│ // End of generated code
 //│ box1: Box[1]
 //│     = Box { inner: 1 }
@@ -92,7 +89,6 @@ def MyBox inner info = MyBox { inner; info }
 //│     info: info
 //│   }));
 //│ };
-//│ res = MyBox1;
 //│ // End of generated code
 //│ MyBox: (int & 'inner) -> (string & 'info) -> (MyBox with {info: 'info, inner: 'inner})
 //│      = [Function: MyBox1]
@@ -105,15 +101,12 @@ mb2 = mb.Map (fun x -> x * 3)
 mb2.Get
 //│ // Query 1
 //│ globalThis.mb = MyBox1(1)("hello");
-//│ res = mb;
 //│ // Query 2
 //│ globalThis.mb1 = mb.Inc;
-//│ res = mb1;
 //│ // Query 3
 //│ res = mb1.Get;
 //│ // Query 4
 //│ globalThis.mb2 = mb1.Map((x) => x * 3);
-//│ res = mb2;
 //│ // Query 5
 //│ res = mb2.Get;
 //│ // End of generated code
@@ -168,13 +161,13 @@ def f: Box[?] -> int
 :e
 f(Box{})
 //│ ╔══[ERROR] Type mismatch in application:
-//│ ║  l.169: 	f(Box{})
+//│ ║  l.162: 	f(Box{})
 //│ ║         	^^^^^^^^
 //│ ╟── record literal of type `anything` does not match type `nothing`
-//│ ║  l.169: 	f(Box{})
+//│ ║  l.162: 	f(Box{})
 //│ ║         	     ^^
 //│ ╟── Note: constraint arises from type wildcard:
-//│ ║  l.164: 	def f: Box[?] -> int
+//│ ║  l.157: 	def f: Box[?] -> int
 //│ ╙──       	           ^
 //│ res: error | int
 //│    = <no result>

shared/src/test/diff/codegen/Declare.mls

@@ -26,7 +26,6 @@ def q = 0
 //│ // Query 1 aborted: b and a are not implemented
 //│ // Query 2
 //│ globalThis.q = 0;
-//│ res = q;
 //│ // End of generated code
 //│ c: int
 //│  = <no result>
@@ -87,10 +86,8 @@ def break = 1
 def str = "str"
 //│ // Query 1
 //│ globalThis.break1 = 1;
-//│ res = break1;
 //│ // Query 2
 //│ globalThis.str = "str";
-//│ res = str;
 //│ // End of generated code
 //│ break: 1
 //│      = 1

shared/src/test/diff/codegen/Inheritance.mls

@@ -230,7 +230,6 @@ checkS p && checkR p && checkQ p && checkP p
 //│   r: 0,
 //│   p: 0
 //│ });
-//│ res = p;
 //│ // Query 2
 //│ res = checkS(p) && checkR(p) && checkQ(p) && checkP(p);
 //│ // End of generated code

shared/src/test/diff/codegen/Parentheses.mls

@@ -33,7 +33,6 @@ x = 0
 x > 0 && x < 0
 //│ // Query 1
 //│ globalThis.x = 0;
-//│ res = x;
 //│ // Query 2
 //│ res = x > 0 && x < 0;
 //│ // End of generated code

shared/src/test/diff/codegen/Polyfill.mls

@@ -42,7 +42,6 @@ def add x y = x + y + x + y
 //│ globalThis.add = function add(x) {
 //│   return (y) => x + y + x + y;
 //│ };
-//│ res = add;
 //│ // End of generated code
 //│ add: int -> int -> int
 //│    = [Function: add]
@@ -86,7 +85,6 @@ n = 123 with { x = 1 }
 //│ }
 //│ // Query 1
 //│ globalThis.n = withConstruct(123, { x: 1 });
-//│ res = n;
 //│ // End of generated code
 //│ n: 123 & {x: 1}
 //│  = [Number: 123] { x: 1 }

shared/src/test/diff/codegen/Recursion.mls

@@ -8,7 +8,6 @@ rec def pow0 n x =
 //│ globalThis.pow0 = function pow0(n) {
 //│   return (x) => n > 0 ? pow0(n - 1)(x) * x : 1;
 //│ };
-//│ res = pow0;
 //│ // End of generated code
 //│ pow0: int -> int -> int
 //│     = [Function: pow0]
@@ -31,7 +30,6 @@ def pow1 x =
 //│     return n > 0 ? go(n - 1) * x : 1;
 //│   }));
 //│ };
-//│ res = pow1;
 //│ // End of generated code
 //│ pow1: int -> int -> int
 //│     = [Function: pow1]
@@ -46,7 +44,6 @@ rec def pow2 n = { call = fun x -> if n > 0 then (pow2 (n - 1)).call x * x else
 //│ globalThis.pow2 = function pow2(n) {
 //│   return { call: (x) => n > 0 ? pow2(n - 1).call(x) * x : 1 };
 //│ };
-//│ res = pow2;
 //│ // End of generated code
 //│ pow2: int -> {call: int -> int}
 //│     = [Function: pow2]

shared/src/test/diff/codegen/Res.mls

@@ -56,7 +56,6 @@ res == 4
 def res = 0
 //│ // Query 1
 //│ globalThis.res1 = 0;
-//│ res = res1;
 //│ // End of generated code
 //│ res: 0
 //│    = 0
@@ -74,7 +73,7 @@ res + 1
 :js
 res + 1
 //│ // Query 1
-//│ res = res1 + 1;
+//│ res = res + 1;
 //│ // End of generated code
 //│ res: int
-//│    = 1
+//│    = 2

shared/src/test/diff/codegen/Terms.mls

@@ -131,7 +131,6 @@ f 0
 //│ globalThis.f = function f(x) {
 //│   return x;
 //│ };
-//│ res = f;
 //│ // Query 2
 //│ res = f(0);
 //│ // End of generated code
@@ -248,7 +247,6 @@ def f x = case x of { }
 //│     throw new Error("non-exhaustive case expression");
 //│   })());
 //│ };
-//│ res = f1;
 //│ // End of generated code
 //│ f: nothing -> nothing
 //│  = [Function: f1]
@@ -358,13 +356,11 @@ rcd2 = rcd1 with { x = 1; z = 2 }
 //│   x: "a",
 //│   y: "b"
 //│ };
-//│ res = rcd1;
 //│ // Query 2
 //│ globalThis.rcd2 = withConstruct(rcd1, {
 //│   x: 1,
 //│   z: 2
 //│ });
-//│ res = rcd2;
 //│ // Query 3
 //│ res = [
 //│   rcd1.x,
@@ -390,7 +386,6 @@ a1.x <- 666
 a1.x
 //│ // Query 1
 //│ globalThis.a1 = new M({ x: 233 });
-//│ res = a1;
 //│ // Query 2
 //│ res = (a1.x = 666, []);
 //│ // Query 3
@@ -412,7 +407,6 @@ t1 = (mut "hello", mut true)
 //│   "hello",
 //│   true
 //│ ];
-//│ res = t1;
 //│ // End of generated code
 //│ t1: (mut 'a, mut 'b,)
 //│   where
@@ -443,7 +437,6 @@ muta1 = (mut 1, mut 2, mut 3, mut 4)
 //│   3,
 //│   4
 //│ ];
-//│ res = muta1;
 //│ // End of generated code
 //│ muta1: MutArray[int]
 //│      = <missing implementation>
@@ -476,7 +469,6 @@ xpp a1
 //│ globalThis.xpp = function xpp(rc) {
 //│   return ((_) => rc)((rc.x = rc.x + 1, []));
 //│ };
-//│ res = xpp;
 //│ // Query 2
 //│ res = xpp(a1);
 //│ // End of generated code
@@ -495,7 +487,6 @@ tu._2
 //│   [],
 //│   2
 //│ ];
-//│ res = tu;
 //│ // Query 2
 //│ res = (tu["_1"] = (tu["_2"] = 3, []), []);
 //│ // Query 3

shared/src/test/diff/codegen/TraitMethods.mls

@@ -101,7 +101,6 @@ class B: A & T1
 a = A{}
 //│ // Query 1
 //│ globalThis.a = new A({});
-//│ res = a;
 //│ // End of generated code
 //│ ╔══[ERROR] Instantiation of an abstract type is forbidden
 //│ ║  l.101: 	a = A{}
@@ -129,7 +128,6 @@ b = B{}
 foo b
 //│ // Query 1
 //│ globalThis.b = new B({});
-//│ res = b;
 //│ // Query 2
 //│ res = foo(b);
 //│ // End of generated code
@@ -153,16 +151,16 @@ class BBB: AAA
   method F: int
   method G: 'a -> 'a
 //│ ╔══[ERROR] Overriding method AAA.F without an overriding definition is not allowed.
-//│ ║  l.153: 	  method F: int
+//│ ║  l.151: 	  method F: int
 //│ ║         	         ^^^^^^
 //│ ╟── Note: method definition inherited from
-//│ ║  l.149: 	  method F = 1
+//│ ║  l.147: 	  method F = 1
 //│ ╙──       	         ^^^^^
 //│ ╔══[ERROR] Overriding method AAA.G without an overriding definition is not allowed.
-//│ ║  l.154: 	  method G: 'a -> 'a
+//│ ║  l.152: 	  method G: 'a -> 'a
 //│ ║         	         ^^^^^^^^^^^
 //│ ╟── Note: method definition inherited from
-//│ ║  l.151: 	  method G x = x
+//│ ║  l.149: 	  method G x = x
 //│ ╙──       	         ^^^^^^^
 //│ Defined type alias Id[+X]
 //│ Defined class AAA
@@ -193,7 +191,7 @@ C.Foo
 :e
 fun x -> x.Foo
 //│ ╔══[ERROR] Implicit call to method Foo is forbidden because it is ambiguous.
-//│ ║  l.194: 	fun x -> x.Foo
+//│ ║  l.192: 	fun x -> x.Foo
 //│ ║         	         ^^^^^
 //│ ╟── Unrelated methods named Foo are defined by:
 //│ ╟── • trait T0
@@ -203,10 +201,10 @@ fun x -> x.Foo
 //│ ║  l.41: 	trait T1
 //│ ║        	      ^^
 //│ ╟── • trait T3
-//│ ║  l.178: 	trait T3
+//│ ║  l.176: 	trait T3
 //│ ║         	      ^^
 //│ ╟── • trait T4
-//│ ║  l.180: 	trait T4
+//│ ║  l.178: 	trait T4
 //│ ╙──       	      ^^
 //│ res: anything -> error
 //│    = [Function: res]