fix pretty-printing of handle blocks and fix tests broken by handle-with syntax

parser-typechecker/src/Unison/TermPrinter.hs

@@ -195,12 +195,22 @@ pretty0
       elideFQN im $ PrettyPrintEnv.termName n (Referent.Con ref i CT.Data)
     Request' ref i -> styleHashQualified'' (fmt S.Request) $
       elideFQN im $ PrettyPrintEnv.termName n (Referent.Con ref i CT.Effect)
-    Handle' h body -> let (imBody, usesBody) = calcImports im body
-                          (imH, usesH) = calcImports im h in
-      paren (p >= 2)
-        $ (fmt S.ControlKeyword "handle" `PP.hang` usesBody [pretty0 n (ac 2 Block imBody doc) body])
+    Handle' h body -> paren (p >= 2) $
+      if height > 0 then PP.lines [
+        (fmt S.ControlKeyword "handle") `PP.hang` pb,
+        (fmt S.ControlKeyword "with") `PP.hang` ph
+       ]
+      else PP.spaced [
+        (fmt S.ControlKeyword "handle") `PP.hang` pb
           <> PP.softbreak
-        <> (fmt S.ControlKeyword "with" `PP.hang` usesH [pretty0 n (ac 2 Block imH doc) h])
+          <> (fmt S.ControlKeyword "with") `PP.hang` ph
+      ]
+      where
+        height = PP.preferredHeight pb `max` PP.preferredHeight ph
+        pb = pblock body
+        ph = pblock h
+        pblock tm = let (im', uses) = calcImports im tm
+                    in uses $ [pretty0 n (ac 0 Block im' doc) tm]
     App' x (Constructor' DD.UnitRef 0) ->
       paren (p >= 11) $ (fmt S.DelayForceChar $ l "!") <> pretty0 n (ac 11 Normal im doc) x
     LamNamed' v x | (Var.name v) == "()" ->

parser-typechecker/tests/Unison/Test/TermParser.hs

@@ -82,13 +82,15 @@ test1 = scope "termparser" . tests . map parses $
     "  x + 1 )"
   --
   -- Handlers
-  ,"handle foo in \n" ++
+  , "handle\n" ++
     "  x = 23 + 42\n" ++
-    "  x + foo 8 102.0 +4"
-  , "handle foo in \n" ++
+    "  x + foo 8 102.0 +4\n" ++
+    "with foo"
+  , "handle\n" ++
     "  x = 1\n" ++
-    "  x"
-  , "handle foo in x"
+    "  x\n" ++
+    "with foo"
+  , "handle x with foo"
 
   -- Patterns
   , "case x of x -> x"

parser-typechecker/tests/Unison/Test/TermPrinter.hs

@@ -124,7 +124,7 @@ test = scope "termprinter" . tests $
   , tc "List.empty"
   , tc "None"
   , tc "Optional.None"
-  , tc "handle foo in bar"
+  , tc "handle foo with bar"
   , tc "Cons 1 1"
   , tc "let\n\
        \  x = 1\n\
@@ -160,13 +160,13 @@ test = scope "termprinter" . tests $
   , pending $ tc "case e of { () -> k } -> z" -- TODO doesn't parse since 'many leaf' expected before the "-> k"
                                               -- need an actual effect constructor to test this with
   , tc "if a then if b then c else d else e"
-  , tc "handle foo in (handle bar in baz)"
+  , tc "handle handle foo with bar with baz"
   , tcBreaks 16 "case (if a then\n\
                  \  b\n\
                  \else c) of\n\
                  \  112 -> x"        -- dodgy layout.  note #517 and #518
-  , tc "handle Pair 1 1 in bar"
-  , tc "handle x -> foo in bar"
+  , tc "handle bar with Pair 1 1"
+  , tc "handle bar with x -> foo"
   , tcDiffRtt True "let\n\
                      \  x = (1 : Int)\n\
                      \  (x : Int)"
@@ -248,12 +248,13 @@ test = scope "termprinter" . tests $
                  \  baz.f : Int -> Int\n\
                  \  baz.f x = x\n\
                  \  13"
-  , pending $ tcBreaks 90 "handle foo in\n\
+  , tcBreaks 90 "handle\n\
                  \  a = 5\n\
                  \  b =\n\
                  \    c = 3\n\
                  \    true\n\
-                 \  false"  -- TODO comes back out with line breaks around foo
+                 \  false\n\
+                 \with foo"
   , tcBreaks 50 "case x of\n\
                  \  true ->\n\
                  \    d = 1\n\
@@ -419,28 +420,24 @@ test = scope "termprinter" . tests $
                  \else\n\
                  \  use A X.c YY.c\n\
                  \  g X.c X.c YY.c YY.c"
-  , tcBreaks 20 "handle bar in\n\
-                 \  (if foo then\n\
+  , tcBreaks 20 "handle\n\
+                 \  if foo then\n\
                  \    use A.X c\n\
                  \    f c c\n\
                  \  else\n\
                  \    use A.Y c\n\
-                 \    g c c)"  -- questionable parentheses, issue #517
+                 \    g c c\n\
+                 \with bar"
   , tcBreaks 28 "if foo then\n\
                  \  f (x : (∀ t. Pair t t))\n\
                  \else\n\
                  \  f (x : (∀ t. Pair t t))"
-  , tcDiffRtt False "handle foo in\n\
+  , tcBreaks 15 "handle\n\
                 \  use A x\n\
-                      \  (if f x x then\n\
+                \  if f x x then\n\
                 \    x\n\
-                      \  else y)"  -- missing break before 'then', issue #518; surplus parentheses #517
-                      "handle foo\n\
-                      \in\n\
-                      \  use A x\n\
-                      \  (if f x x then\n\
-                      \    x\n\
-                      \  else y)" 15  -- parser doesn't like 'in' beginning a line
+                \  else y\n\
+                \with foo"  -- missing break before 'then', issue #518
   , tcBreaks 20 "case x of\n\
                  \  () ->\n\
                  \    use A y\n\
@@ -450,9 +447,10 @@ test = scope "termprinter" . tests $
                  \  f x x\n\
                  \  c = g x x\n\
                  \  h x x"
-  , tcBreaks 15 "handle foo in\n\
+  , tcBreaks 15 "handle\n\
                  \  use A x\n\
-                 \  f x x"
+                 \  f x x\n\
+                 \with foo"
   , tcBreaks 15 "let\n\
                  \  c =\n\
                  \    use A x\n\
@@ -466,11 +464,12 @@ test = scope "termprinter" . tests $
                  \    a =\n\
                  \      use A B.x\n\
                  \      f B.x B.x\n\
-                 \      handle foo in\n\
+                 \      handle\n\
                  \        q =\n\
                  \          use A.B.D x\n\
                  \          h x x\n\
                  \        foo\n\
+                 \      with foo\n\
                  \    bar\n\
                  \  _ ->\n\
                  \    b =\n\
@@ -479,9 +478,10 @@ test = scope "termprinter" . tests $
                  \    bar"
   , tcBreaks 20 "let\n\
                  \  a =\n\
-                 \    handle foo in\n\
+                 \    handle\n\
                  \      use A x\n\
                  \      f x x\n\
+                 \    with foo\n\
                  \  bar"
   , tcBreaks 16 "let\n\
                  \  a =\n\

parser-typechecker/tests/Unison/Test/Typechecker/TypeError.hs

@@ -40,7 +40,7 @@ test = scope "> extractor" . tests $
         "xyz default abort = case abort of\n" ++
         "  {a} -> 3\n" ++
         "  {Abort.abort -> k} ->\n" ++
-        "    handle xyz default in k 100\n"
+        "    handle k 100 with xyz default\n"
       ) Err.matchBody
   ]
   where y, n :: String -> ErrorExtractor Symbol Ann a -> Test ()

unison-src/tests/abort.u

@@ -6,8 +6,8 @@ eff f z e = case e of
   { Abort.Abort _ -> k } -> z
   { a } -> f a
 -- heff : Nat
-heff = handle eff (x -> x Nat.+ 2) 1 in Abort.Abort ()
+heff = handle Abort.Abort () with eff (x -> x Nat.+ 2) 1
 hudy : Nat
-hudy = handle eff (x -> x Nat.+ 2) 1 in 42
+hudy = handle 42 with eff (x -> x Nat.+ 2) 1
 bork : () -> {Abort} Nat
 bork = u -> 1 Nat.+ (Abort.Abort ())

unison-src/tests/cce.u

@@ -32,10 +32,10 @@ Remote.runLocal : '{Remote} a -> a
 Remote.runLocal r =
   step nid r = case r of
     {a} -> a
-    {Remote.fork t -> k} -> handle (step nid) in k (Future.fromThunk t)
-    {Remote.spawn -> k} -> handle (step (Node.increment nid)) in k nid
-    {Remote.at _ t -> k} -> handle (step nid) in k !t
-  handle (step (Node.Node 0)) in !r
+    {Remote.fork t -> k} -> handle k (Future.fromThunk t) with step nid
+    {Remote.spawn -> k} -> handle k nid with step (Node.increment nid)
+    {Remote.at _ t -> k} -> handle k !t with step nid
+  handle !r with step (Node.Node 0)
 
 Remote.forkAt : Node -> '{Remote} a ->{Remote} (Future a)
 Remote.forkAt node r = Remote.fork '(Remote.at node r)

unison-src/tests/console.u

@@ -15,8 +15,8 @@ namespace Console where
 
   state : s -> Request (State s) a -> a
   state s c = case c of
-    {State.get -> k} -> handle state s in k s
-    {State.set s' -> k} -> handle state s' in k ()
+    {State.get -> k} -> handle k s with state s
+    {State.set s' -> k} -> handle k () with state s'
     {a} -> a
 
   simulate : Request Console d -> {State ([Text], [Text])} d
@@ -29,24 +29,26 @@ namespace Console where
       -- this really should typecheck but doesn't for some reason
       -- error is that `simulate` doesn't check against `Request Console c -> r`,
       -- but seems like that `r` should get instantiated as `{State (..)} c`.
-      handle simulate in k (at 0 ins)
+      handle k (at 0 ins) with simulate
     {Console.write t -> k} ->
       io = State.get
       ins = fst io
       outs = snd io
       -- same deal here
-      handle simulate in k (State.set (ins, cons t outs))
+      handle k (State.set (ins, cons t outs)) with simulate
     {a} -> a
 
 (++) = (Text.++)
 
-x = handle Console.state ([],[]) in
-      handle Console.simulate in
+x = handle
+      handle
         use Console read write
         use Optional Some None
         write "What's your name?"
         case read of
           Some name -> write ("Hello" ++ name)
           None -> write "Fine, be that way."
+      with Console.simulate
+    with Console.state ([],[])
 
 > x

unison-src/tests/console1.u

@@ -19,24 +19,27 @@ namespace Console where
 
   simulate : Request Console a -> {State ([Text], [Text])} a
   simulate c = case c of
-    {Console.read -> k} -> handle simulate in
+    {Console.read -> k} -> handle
         io = State.get
         ins = fst io
         outs = snd io
         State.set (drop 1 ins, outs)
         k (at 0 ins)
-    {Console.write t -> k} -> handle simulate in
+      with simulate
+
+    {Console.write t -> k} -> handle
         io = State.get
         ins = fst io
         outs = snd io
         State.set (ins, outs ++ [t])
         k ()
+      with simulate
 
-e = 'let handle simulate in
+e = 'let handle
     use Console read write
     use Optional Some None
     write "What's your name?"
     case read of
       Some name -> write ("Hello" ++ name)
       None -> write "Fine, be that way."
-
+  with simulate

unison-src/tests/handler-stacking.u

@@ -1,9 +1,11 @@
 use State get put
 use Writer tell
 
-> handle stateHandler "hello" in
-  handle writerHandler [] in
-  replicate 5 main
+> handle
+    handle replicate 5 main
+    with writerHandler []
+  with stateHandler "hello"
+
 
 main = '(tell get)
 
@@ -22,11 +24,11 @@ ability Writer w where
 
 stateHandler : s -> Request {State s} a -> (s, a)
 stateHandler s x = case x of
-  { State.get -> k } -> handle stateHandler s in k s
-  { State.put s -> k } -> handle stateHandler s in k ()
+  { State.get -> k } -> handle k s with stateHandler s
+  { State.put s -> k } -> handle k () with stateHandler s
   { a } -> (s, a)
 
 writerHandler : [w] -> Request {Writer w} a -> ([w], a)
 writerHandler ww x = case x of
-  { Writer.tell w -> k } -> handle writerHandler (ww `snoc` w) in k ()
+  { Writer.tell w -> k } -> handle k () with writerHandler (ww `snoc` w)
   { a } -> (ww, a)

unison-src/tests/hang.u

@@ -31,10 +31,10 @@ Remote.runLocal r =
   use Future Future
   step nid r = case r of
     {a} -> a
-    {Remote.fork t -> k} -> handle (step nid) in k (Future t)
-    {Remote.spawn -> k} -> handle (step (Node.increment nid)) in k nid
-    {Remote.at _ t -> k} -> handle (step nid) in k !t
-  handle (step (Node.Node 0)) in !r
+    {Remote.fork t -> k} -> handle k (Future t) with step nid
+    {Remote.spawn -> k} -> handle k nid with step (Node.increment nid)
+    {Remote.at _ t -> k} -> handle k !t with step nid
+  handle !r with step (Node.Node 0)
 
 Remote.forkAt : Node -> '{Remote} a ->{Remote} (Future a)
 Remote.forkAt node r = Remote.fork '(Remote.at node r)

unison-src/tests/methodical/abilities.u

@@ -6,13 +6,13 @@ ability A where
 
 unA w = case w of
   {a} -> a
-  {A.woot -> k} -> handle unA in k 10
+  {A.woot -> k} -> handle k 10 with unA
 
 -- This verifies that the continuation captures local variables
-a1 = handle unA in
+a1 = handle
     x = 42
     y = A.woot
     x
+  with unA
 
 > a1 -- should be 42
-

unison-src/tests/methodical/overapply-ability.u

@@ -8,31 +8,33 @@ ability Zing where
 
 unzing z = case z of
   {a} -> a
-  {Zing.zing n -> k} -> handle unzing in k (x -> x `drop` n)
-  {Zing.zing2 n1 n2 -> k} -> handle unzing in k (n3 n4 -> [n1, n2, n3, n4])
+  {Zing.zing n -> k} -> handle k (x -> x `drop` n) with unzing
+  {Zing.zing2 n1 n2 -> k} -> handle k (n3 n4 -> [n1, n2, n3, n4]) with unzing
 
-exacth = handle unzing in
+exacth = handle
   f = Zing.zing 3
   f 20 + 1
+  with unzing
 
-overapplyh = handle unzing in
+overapplyh = handle
   Zing.zing 3 20 + 1
+  with unzing
 
 -- SEQUENCES with abilities
 
-sequence1 = handle unzing in [Zing.zing 1 4]
-sequence2 = handle unzing in [Zing.zing 1 4, Zing.zing 1 4]
-sequence3 = handle unzing in [Zing.zing 1 4, Zing.zing 2 4, Zing.zing 3 4, Zing.zing 4 4]
+sequence1 = handle [Zing.zing 1 4] with unzing
+sequence2 = handle [Zing.zing 1 4, Zing.zing 1 4] with unzing
+sequence3 = handle [Zing.zing 1 4, Zing.zing 2 4, Zing.zing 3 4, Zing.zing 4 4] with unzing
 
 -- Overapply of requests
 
-overapplyh2 = handle unzing in Zing.zing2 1 2 3 4
+overapplyh2 = handle Zing.zing2 1 2 3 4 with unzing
 
-overapplyh3a = handle unzing in Zing.zing2 1 2 3 4 ++ [5]
+overapplyh3a = handle Zing.zing2 1 2 3 4 ++ [5] with unzing
 
-overapplyh3b = handle unzing in Zing.zing2 1 2 3 4 ++ [5, Zing.zing 2 8]
+overapplyh3b = handle Zing.zing2 1 2 3 4 ++ [5, Zing.zing 2 8] with unzing
 
-overapplyh3c = handle unzing in Zing.zing2 1 2 3 4 ++ [5, Zing.zing 2 7 + 1]
+overapplyh3c = handle Zing.zing2 1 2 3 4 ++ [5, Zing.zing 2 7 + 1] with unzing 
 
 > (exacth,
    overapplyh,

unison-src/tests/multiple-effects.u

@@ -9,8 +9,8 @@ ability Console where
 namespace Console where
   state : s -> Request (State s) a -> a
   state s c = case c of
-    {State.get -> k} -> handle state s in k s
-    {State.set s' -> k} -> handle state s' in k ()
+    {State.get -> k} -> handle k s with state s
+    {State.set s' -> k} -> handle k () with state s'
     {a} -> a
 
 multiHandler : s -> [w] -> Nat -> Request {State s, Console} a -> ()

unison-src/tests/soe.u

@@ -31,10 +31,10 @@ Remote.runLocal r =
   use Future Future
   step nid r = case r of
     {a} -> a
-    {Remote.fork t -> k} -> handle (step nid) in k (Future t)
-    {Remote.spawn -> k} -> handle (step (Node.increment nid)) in k nid
-    {Remote.at _ t -> k} -> handle (step nid) in k !t
-  handle (step (Node.Node 0)) in !r
+    {Remote.fork t -> k} -> handle k (Future t) with step nid
+    {Remote.spawn -> k} -> handle k nid with step (Node.increment nid)
+    {Remote.at _ t -> k} -> handle k !t with step nid
+  handle !r with step (Node.Node 0)
 
 Remote.forkAt : Node -> '{Remote} a ->{Remote} (Future a)
 Remote.forkAt node r = Remote.fork '(Remote.at node r)

unison-src/tests/state1.u

@@ -5,8 +5,8 @@ ability State se2 where
 
 -- state : ∀ s a . s -> Request (State s) a -> (s, a)
 state woot eff = case eff of
-  { State.put snew -> k } -> handle (state snew) in k ()
-  { State.get () -> k } -> handle state woot in k woot
+  { State.put snew -> k } -> handle k () with state snew
+  { State.get () -> k } -> handle k woot with state woot 
   { a } -> (woot, a)
 
 blah : ∀ s a . s -> Request (State s) a -> (s, a)

unison-src/tests/state2.u

@@ -4,8 +4,8 @@ ability State se2 where
   get : ∀ se . () -> {State se} se
 state : ∀ s a . s -> Request (State s) a -> (s, a)
 state woot eff = case eff of
-  { State.get () -> k } -> handle (state woot) in (k woot)
-  { State.put snew -> k } -> handle (state snew) in (k ())
+  { State.get () -> k } -> handle k woot with state woot
+  { State.put snew -> k } -> handle k () with state snew
   { a } -> (woot, a)
 
 > ()

unison-src/tests/state2a-min.u

@@ -4,13 +4,14 @@ ability State s where
 
 state : s -> Request (State s) a -> a
 state s eff = case eff of
-  { State.put snew -> k } -> handle (state snew) in k ()
+  { State.put snew -> k } -> handle k () with state snew
   { a } -> a
 
 ex : Text
-ex = handle (state 10) in
+ex = handle
   State.put (11 + 1)
   State.put (5 + 5)
   "hello"
+  with state 10
 
 > ex

unison-src/tests/state2a.u

@@ -8,8 +8,8 @@ ability State s where
 
 state : s -> Request (State s) a -> (s, a)
 state s eff = case eff of
-  { State.get -> k } -> handle (state s) in k s
-  { State.put snew -> k } -> handle (state snew) in k ()
+  { State.get -> k } -> handle k s with state s
+  { State.put snew -> k } -> handle k () with state snew
   { a } -> (s, a)
 
 modify : (s ->{} s) ->{State s} ()
@@ -30,11 +30,12 @@ first p = case p of (a,_) -> a
 ex : Text
 ex =
   result : (Nat, Text)
-  result = handle (state 10) in
+  result = handle
       State.put (11 + 1)
       x = State.get
       State.put (5 + 5)
       "hello"
+    with state 10
 
   second result
 
@@ -47,5 +48,3 @@ modify2 f =
   State.put s2
 
 ---
-
-

unison-src/tests/state2b-min.u

@@ -4,11 +4,12 @@ ability State s where
 
 state : s -> Request (State s) a -> s
 state s eff = case eff of
-  { State.put snew -> k } -> handle (state snew) in k ()
+  { State.put snew -> k } -> handle k () with state snew
   { a } -> s
 
-> handle (state 10) in
+> handle
   State.put (11 + 1)
   State.put (5 + 15)
   ()
+  with state 10
   -- should be 20

unison-src/tests/state2b.u

@@ -8,8 +8,8 @@ ability State s where
 
 state : s -> Request (State s) a -> (s, a)
 state s eff = case eff of
-  { State.get -> k } -> handle (state s) in k s
-  { State.put snew -> k } -> handle (state snew) in k ()
+  { State.get -> k } -> handle k s with state s
+  { State.put snew -> k } -> handle k () with state snew
   { a } -> (s, a)
 
 modify : (s ->{} s) -> {State s} ()
@@ -26,14 +26,14 @@ first p = case p of (a,_) -> a
 
 ex : Nat
 ex =
-  result = handle (state 10) in
+  result = handle
     State.put (11 + 1)
     State.put (5 + 15)
     ()
+    with state 10
 
   first result
 
 -- should return `20`, but actually returns `12`
 -- seems like only one `put` is actually being run
 > ex
-

unison-src/tests/state3.u

@@ -5,24 +5,24 @@ ability State se2 where
 
 state : ∀ s a . s -> Request (State s) a -> (s, a)
 state woot eff = case eff of
-  { State.get () -> k } -> handle (state woot) in (k woot)
-  { State.put snew -> k } -> handle (state snew) in (k ())
+  { State.get () -> k } -> handle k woot with state woot
+  { State.put snew -> k } -> handle k () with state snew
   { a } -> (woot, a)
 
 ex1 : (Nat, Nat)
-ex1 = handle (state 42) in State.get ()
+ex1 = handle State.get () with state 42
 
 ex1a : (Nat, Nat)
-ex1a = handle (state 42) in 49
+ex1a = handle 49 with state 42
 
-ex1b = handle (x -> 10) in 0
+ex1b = handle 0 with x -> 10
 
 ex1c : Nat
-ex1c = handle (x -> 10) in 0
+ex1c = handle 0 with x -> 10
 
-ex1d = handle (state 42) in 49
+ex1d = handle 49 with state 42
 
-ex2 = handle (state 42) in State.get ()
+ex2 = handle State.get () with state 42
 
 ex3 : (Nat, Nat)
 ex3 = ex2

unison-src/tests/state4.u

@@ -4,8 +4,8 @@ ability State s where
 
 state : s -> Request (State s) a -> s
 state s eff = case eff of
-  { State.get -> k } -> handle (state s) in k s
-  { State.put snew -> k } -> handle (state snew) in k ()
+  { State.get -> k } -> handle k s with state s
+  { State.put snew -> k } -> handle k () with state snew
   { a } -> s
 
 modify : (s ->{} s) -> {State s} ()
@@ -15,11 +15,12 @@ increment : '{State Nat} ()
 increment = '(modify ((+) 1))
 
 ex : Nat
-ex = handle (state 10) in
+ex = handle
   State.put (11 + 1)
   !increment
   !increment
   !increment
   State.get -- should be 15, amirite??
+  with state 10
 
 > ex

unison-src/tests/state4a.u

@@ -4,8 +4,8 @@ ability State s where
 
 state : s -> Request (State s) a -> s
 state s eff = case eff of
-  { State.get -> k } -> handle (state s) in k s
-  { State.put snew -> k } -> handle (state snew) in k ()
+  { State.get -> k } -> handle k s with state s
+  { State.put snew -> k } -> handle k () with state snew
   { a } -> s
 
 modify : (s ->{} s) -> {State s} ()
@@ -15,11 +15,12 @@ increment : '{State Nat} ()
 increment = '(modify ((+) 1))
 
 ex : Nat
-ex = handle (state 10) in
+ex = handle
   State.put (11 + 1)
   -- !increment
   -- !increment
   -- !increment
   State.get -- should be 15, amirite??
+  with state 10
 
 > ex

unison-src/tests/stream.u

@@ -35,9 +35,9 @@ namespace Stream where
         if n Nat.== 0 then ()
         else
           Emit.emit a
-          handle step (n `drop` 1) in k ()
+          handle k () with step (n `drop` 1)
       {r} -> ()
-    Stream ' handle step n in run s
+    Stream ' handle run s with step n
 
   -- map : (a -> b) -> Stream {e} a r -> Stream {e} b r
   map f s =
@@ -45,15 +45,15 @@ namespace Stream where
       {r} -> r
       {Emit.emit a -> k} ->
         Emit.emit (f a)
-        handle step in k ()
-    Stream ' handle step in run s
+        handle k () with step
+    Stream ' handle run s with step
 
   -- toSeq : Stream {e} a r ->{e} [a]
   toSeq s =
     step acc e = case e of
-      {Emit.emit a -> k} -> handle step (acc `snoc` a) in k ()
+      {Emit.emit a -> k} -> handle k () with step (acc `snoc` a)
       {_} -> acc
-    handle step [] in run s
+    handle run s with step []
 
   fromSeq : [a] -> Stream e a ()
   fromSeq a =