experimental cps detection via scope injection

cps.nim

@@ -19,7 +19,7 @@
 
 # we only support panics because we don't want to run finally on defect
 when not defined(nimPanics):
   {.warning: "cps supports --panics:on only; " &
              " see https://github.com/nim-works/cps/issues/110".}
 
 when (NimMajor, NimMinor, NimPatch) < (1, 7, 3):
@@ -76,19 +76,29 @@
     else:
       result = getAst(cpsTransform(tipe, n))
 
-macro cps*(tipe: typed, n: untyped): untyped =
+macro cpsMarkExtract(n: untyped): untyped =
+  let cpsExtract = bindSym"cpsExtract"
+  result = nnkPragmaBlock.newTree(
+    nnkPragma.newTree(cpsExtract),
+    n
+  )
+
+template cps*(tipe: typed, n: untyped): untyped =
   ## When applied to a procedure, rewrites the procedure into a
   ## continuation form. When applied to a procedure type definition,
   ## rewrites the type into a callback form.
-  result = n
+  bind cpsTyped
+  bind cpsScalpel
+  bind cpsMarkExtract
+
   when not defined(nimdoc):
-    # add the application of the typed transformation pass
-    n.addPragma:
-      nnkExprColonExpr.newTree(bindSym"cpsTyped", tipe)
-    # let the untyped pass do what it will with this input
-    # XXX: currently disabled because it's a slipperly slope of regret
-    #result = performUntypedPass(T, n)
-    result = n
+    cpsScalpel:
+      const isInCps {.inject.} = true
+
+      cpsMarkExtract:
+        cpsTyped(tipe, n)
+  else:
+    n
 
 proc adaptArguments(sym: NormNode; args: seq[NormNode]): seq[NormNode] =
   ## convert any arguments in the list as necessary to match those of
@@ -232,7 +242,7 @@
   let tipe = getTypeInst c
   if not tipe.isNilOrVoid:
     # assign the continuation to a variable to prevent re-evaluation
     let continuation {.inject.} = nskLet.genSym"continuation"
     result.add:
       # assign the input to a variable that can be repeated evaluated
       nnkLetSection.newTree:

cps/normalizedast.nim

@@ -267,7 +267,7 @@ defineToNimNodeConverter(
 allowAutoDowngradeNormalizedNode(
     Name, TypeExpr, Call, Conv, PragmaStmt, PragmaAtom, IdentDef, RoutineDef,
     ProcDef, FormalParams, RoutineParam, VarSection, LetSection, VarLet,
-    VarLetIdentDef, VarLetTuple, DefVarLet, IdentDefLet, Sym
+    VarLetIdentDef, VarLetTuple, DefVarLet, IdentDefLet, Sym, PragmaBlock
   )
 
 # types that go from a specific type to a less specific type, "downgrade"

cps/spec.nim

@@ -22,7 +22,7 @@
       true
 
 import cps/[rewrites, help, normalizedast]
 export errorAst, desym, isEmpty, genField
 
 template cpsLift*() {.pragma.}          ## lift this proc|type
 template cpsCall*() {.pragma.}          ## a cps call
@@ -50,6 +50,7 @@
 template cpsHasException*(cont, ex: typed) {.pragma.}  ##
 ## the continuation has an exception stored in `ex`, with `cont` being the
 ## continuation symbol used.
+template cpsExtract*() {.pragma.} ## extract this block from the scope
 
 const
   cpsStackFrames* {.booldefine, used.} = compileOption"stacktrace"
@@ -101,7 +102,7 @@
 proc `=copy`(dest: var ContinuationObj; src: ContinuationObj) {.error.} =
   discard
 
 proc `=destroy`(dest: var ContinuationObj) =
   for key, value in dest.fieldPairs:
     reset value
 

cps/transform.nim

@@ -975,6 +975,13 @@
   result = floater:
     copyNimTree n
 
+macro cpsScalpel*(n: typed): untyped =
+  ## returns the first `{.cpsExtract.}` block from `n`
+  debugAnnotation cpsScalpel, n:
+    it = it.findChildRecursive() do (n: NormNode) -> bool:
+      n.kind == nnkPragmaBlock and n.asPragmaBlock().hasPragma("cpsExtract")
+    it = it.last
+
 macro cpsManageException(name: static[string]; n: typed): untyped =
   ## rewrites all continuations in `n` containing an exception so that exception
   ## become the "current" exception of that continuation while preserving the
@@ -1080,7 +1087,7 @@
   ## rewrites all continuations in `n` so that any unhandled exception will
   ## be first copied into the `ex` variable, then raise
 
   {.warning: "compiler workaround here, see: https://github.com/nim-lang/Nim/issues/18352".}
   let contType = contType
 
   proc handle(n: NormNode): NormNode =
@@ -1205,7 +1212,7 @@
   n.pragma.add bindName"cpsCont"
 
   # run other stages
   {.warning: "compiler bug workaround, see: https://github.com/nim-lang/Nim/issues/18349".}
   let processMainContinuation =
     newCall(bindSym"cpsFloater"):
       newCall(bindSym"cpsResolver", NimNode env.identity, NimNode env.root):