Expose lifter problem with loops

Author: LPTK

hkmc2/shared/src/main/scala/hkmc2/codegen/js/JSBuilder.scala

@@ -396,6 +396,9 @@ class JSBuilder(using TL, State, Ctx) extends CodeBuilder:
 
     case Label(lbl, bod, rst) =>
       scope.allocateName(lbl)
+      
+      // [fixme:0] TODO check scope and allocate local variables here (see: https://github.com/hkust-taco/mlscript/pull/293#issuecomment-2792229849)
+      
       doc" # ${getVar(lbl)}: while (true) { #{ ${
         returningTerm(bod, endSemi = false)
       } # break; #}  # }${returningTerm(rst, endSemi)}"

hkmc2/shared/src/test/mlscript/lifter/Loops.mls

@@ -0,0 +1,76 @@
+:js
+:lift
+
+
+let fs = []
+//│ fs = []
+
+fun foo() =
+  let x = 1
+  while x < 5 do
+    set x += 1
+    fs.push of () => x
+
+:expect 5
+foo()
+fs.0()
+//│ = 5
+
+
+let fs = []
+//│ fs = []
+
+fun foo() =
+  let i = 1
+  while i < 5 do
+    let x = i
+    set i += 1
+    fs.push of () => x
+
+// * Note that this also fails without lifting, as we need to fix [fixme:0]
+:fixme
+:expect 1
+foo()
+fs.0()
+//│ ═══[RUNTIME ERROR] Expected: '1', got: '4'
+//│ = 4
+
+
+:sjs
+fun foo() =
+  let x = 1
+  while true do
+    set x += 1
+    return () => x
+//│ JS (unsanitized):
+//│ let foo2, lambda2, lambda$2;
+//│ lambda$2 = function lambda$(x) {
+//│   return x
+//│ };
+//│ lambda2 = (undefined, function (x) {
+//│   return () => {
+//│     return lambda$2(x)
+//│   }
+//│ });
+//│ foo2 = function foo() {
+//│   let x, scrut, tmp2, tmp3;
+//│   x = 1;
+//│   tmp4: while (true) {
+//│     scrut = true;
+//│     if (scrut === true) {
+//│       tmp2 = x + 1;
+//│       x = tmp2;
+//│       return runtime.safeCall(lambda2(x))
+//│     } else {
+//│       tmp3 = runtime.Unit;
+//│     }
+//│     break;
+//│   }
+//│   return tmp3
+//│ };
+
+:expect 2
+foo()()
+//│ = 2
+
+

hkmc2/shared/src/test/mlscript/lifter/Mutation.mls

@@ -0,0 +1,67 @@
+:lift
+:js
+
+
+let xs = []
+//│ xs = []
+
+fun foo() =
+  let x = 1
+  fun bar() = x
+  xs.push(bar)
+  set x = 2
+
+:expect 2
+foo()
+xs.0()
+//│ = 2
+
+
+let xs = []
+//│ xs = []
+
+// :sjs
+fun foo() =
+  let x
+  fun bar() = x
+  xs.push(bar)
+  x = 2
+
+:expect 2
+foo()
+xs.0()
+//│ = 2
+
+
+fun foo() =
+  let x
+  fun bar() =
+    x = 2
+  [bar, () => x]
+
+:expect 2
+let b_x = foo()
+b_x.0()
+b_x.1()
+//│ = 2
+//│ b_x = [[function], [function]]
+
+
+:sjs
+fun foo() =
+  fun bar() =
+    let x
+    x
+  bar
+//│ JS (unsanitized):
+//│ let bar3, foo3;
+//│ bar3 = function bar() {
+//│   let x;
+//│   x = undefined;
+//│   return x
+//│ };
+//│ foo3 = function foo() {
+//│   return bar3
+//│ };
+
+