fix issue #177

NEWS.md

@@ -1,5 +1,7 @@
 ## MLKit NEWS
 
+* mael 2024-06-27: Fix recursive-function specialisation bug (issue #177).
+
 ### MLKit version 4.7.11 is released
 
 * mael 2024-06-04: Tooling bug fixes.

src/Compiler/Lambda/OptLambda.sml

@@ -797,6 +797,7 @@ structure OptLambda : OPT_LAMBDA =
    fun elim_app_arg lv n (e as APP(lv_e as VAR{lvar,...},PRIM(UB_RECORDprim,args),tailpos)) =
        if Lvars.eq(lvar,lv) then
          let val (_,args) = pick n args
+             val args = map (elim_app_arg lv n) args
          in APP(lv_e,ubargs args,tailpos)
          end
        else map_lamb (elim_app_arg lv n) e

test/all.tst

@@ -178,4 +178,5 @@ structs-avail.sml                             (* basis library available structu
 
 word-n-vector.sml
 int-n-vector.sml
-auto2.sml                                     (* ffi auto-conversion *)
+auto2.sml                                     (* ffi auto-conversion *)
+foldbug.sml

test/foldbug.sml

@@ -0,0 +1,8 @@
+datatype 'a tree = L | T of 'a tree * 'a * 'a tree
+
+fun fold (_, L, acc) = acc
+  | fold (f, T (l, x, r), acc) = fold (f, l, (f (x, fold (f, r, acc))))
+
+val v = fold (fn (x, a) => x+a, T(L,40,T(L,2,L)), 0)
+
+val () = print (Int.toString v ^ "\n")

test/foldbug.sml.out.ok

@@ -0,0 +1 @@
+42