fix: restore the missing Data.Array.ST.clone

changelog.d/20260713_180352_st_clone.md

@@ -0,0 +1,7 @@
+### Fixed
+
+- `Data.Array.ST` exports `clone` again: upstream v7.3.0 declares
+  `clone`/`cloneImpl` (`STFn1`), but the fork carried neither, so code using
+  `Data.Array.ST.clone` failed to compile against the fork. The Lua module
+  now provides `cloneImpl`, the same independent copy the FFI already uses
+  for `thawImpl`/`freezeImpl`.

src/Data/Array/ST.lua

@@ -73,6 +73,7 @@ return {
   unsafeThawImpl = (function(xs) return xs end),
   freezeImpl = (copyImpl),
   thawImpl = (copyImpl),
+  cloneImpl = (copyImpl),
   sortByImpl = ((function()
     local function rshift(x, by) return math.floor(x / 2 ^ by) end
 

src/Data/Array/ST.purs

@@ -24,6 +24,7 @@ module Data.Array.ST
   , sortWith
   , freeze
   , thaw
+  , clone
   , unsafeFreeze
   , unsafeThaw
   , toAssocArray
@@ -95,6 +96,15 @@ thaw = runSTFn1 thawImpl
 -- | Create a mutable copy of an immutable array.
 foreign import thawImpl :: forall h a. STFn1 (Array a) h (STArray h a)
 
+-- | Make a mutable copy of a mutable array.
+clone
+  :: forall h a
+   . STArray h a
+  -> ST h (STArray h a)
+clone = runSTFn1 cloneImpl
+
+foreign import cloneImpl :: forall h a. STFn1 (STArray h a) h (STArray h a)
+
 -- | Sort a mutable array in place. Sorting is stable: the order of equal
 -- | elements is preserved.
 sort :: forall a h. Ord a => STArray h a -> ST h (STArray h a)

test/regression/array_st.lua

@@ -69,6 +69,15 @@ do
   check("thawImpl is independent", copy[1] == 1, "copy mutated to " .. tostring(copy[1]))
 end
 
+-- cloneImpl (the same move-to-fresh-table path) is an independent copy.
+do
+  local xs = {1, 2, 3}
+  local copy = ST.cloneImpl(xs)
+  checkArray("cloneImpl copies", copy, {1, 2, 3})
+  xs[1] = 99
+  check("cloneImpl is independent", copy[1] == 1, "copy mutated to " .. tostring(copy[1]))
+end
+
 -- toAssocArrayImpl builds zero-based {index, value} records.
 do
   local r = ST.toAssocArrayImpl({"a", "b"})