Fix unexpected generalizations

Author: NeilKleistGao

hkmc2/shared/src/main/scala/hkmc2/bbml/bbML.scala

@@ -46,6 +46,7 @@ final case class BbCtx(
   def getRegEnv: Type = outVar match
     case S(v) => v | outRegAcc
     case N => outRegAcc
+  def isTopLevel = parent.isEmpty
 
 
 given (using ctx: BbCtx): Raise = ctx.raise
@@ -283,7 +284,8 @@ class BBTyper(using elState: Elaborator.State, tl: TL):
         val funTy = tryMkMono(res, lam)
         given CCtx = CCtx.init(lam, N)
         constrain(funTy, funTyV)(using ctx)
-        pctx += sym -> PolyType.generalize(funTy, S(outer), 1)
+        if pctx.isTopLevel then // only generalize top-level definitions
+          pctx += sym -> PolyType.generalize(funTy, S(outer), 1)
     case _ => error(msg"Function definition shape not yet supported for ${sym.nme}" -> lam.toLoc :: Nil)
 
   private def typeSplit

hkmc2/shared/src/test/mlscript/bbml/bbExtrude.mls

@@ -91,3 +91,23 @@ f(g)(bar)
 //│ ╟── because: cannot constrain  'B  <:  ¬{Int}
 //│ ╙── because: cannot constrain  ⊤  <:  ¬{Int}
 //│ Type: Int
+
+fun k(x) =
+  fun f(y) = x(y)
+  f(0) + 0
+k
+//│ Type: ['eff] -> (Int ->{'eff} Int) ->{'eff} Int
+
+:e
+k(_ => "")
+//│ ╔══[ERROR] Type error in function literal with expected type 'x
+//│ ║  l.102: 	k(_ => "")
+//│ ║         	       ^^
+//│ ╟── because: cannot constrain  ('_) ->{⊥} (Str)  <:  'x
+//│ ╟── because: cannot constrain  ('_) ->{⊥} (Str)  <:  'x
+//│ ╟── because: cannot constrain  ('_) ->{⊥} (Str)  <:  (Int) ->{'eff} (Int)
+//│ ╙── because: cannot constrain  Str  <:  Int
+//│ Type: Int
+
+k(_ => 42)
+//│ Type: Int

hkmc2/shared/src/test/mlscript/bbml/bbGetters.mls

@@ -31,20 +31,14 @@ test1()
 //│ Type: ⊥
 
 
-:todo // it feels like this should work
 fun test2() =
   fun funny = case
     0 then 0
     n then funny(n - 1) + 1
   funny
-//│ ╔══[ERROR] Expected a monomorphic type or an instantiable type here, but () ->{⊥} [outer, 'caseScrut, 'eff] -> 'caseScrut ->{'eff} Int found
-//│ ║  l.37: 	    0 then 0
-//│ ║        	           ^
-//│ ║  l.38: 	    n then funny(n - 1) + 1
-//│ ║        	^^^^^^^^^^^^^^^^^^^^^^^^^^^
-//│ ║  l.39: 	  funny
-//│ ╙──      	^^^^^^^
-//│ Type: ⊤
+test2
+//│ = [function test2]
+//│ Type: () -> (Int -> Int)
 
 fun test2() =
   fun funny = case
@@ -82,7 +76,7 @@ fun test2() =
     case n then funny(n - 1) + 1
   funny
 //│ ╔══[WARNING] Pure expression in statement position
-//│ ║  l.81: 	    case 0 then 0
+//│ ║  l.75: 	    case 0 then 0
 //│ ╙──      	                ^
 //│ JS (unsanitized):
 //│ let test22;
@@ -104,15 +98,15 @@ fun test2() =
 //│   return tmp1
 //│ };
 //│ ╔══[WARNING] Pure expression in statement position
-//│ ║  l.81: 	    case 0 then 0
+//│ ║  l.75: 	    case 0 then 0
 //│ ╙──      	                ^
 //│ ╔══[ERROR] Function definition shape not yet supported for funny
-//│ ║  l.81: 	    case 0 then 0
+//│ ║  l.75: 	    case 0 then 0
 //│ ║        	                ^
-//│ ║  l.82: 	    case n then funny(n - 1) + 1
+//│ ║  l.76: 	    case n then funny(n - 1) + 1
 //│ ╙──      	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 //│ ╔══[ERROR] Variable not found: funny
-//│ ║  l.83: 	  funny
+//│ ║  l.77: 	  funny
 //│ ╙──      	  ^^^^^
 //│ Type: ⊤
 
@@ -121,7 +115,7 @@ fun test2() =
 fun test3 =
   print("Hi")
 //│ ╔══[ERROR] Function definition shape not yet supported for test3
-//│ ║  l.122: 	  print("Hi")
+//│ ║  l.116: 	  print("Hi")
 //│ ╙──       	  ^^^^^^^^^^^
 //│ Type: ⊤