Generate dataspace patterns from Nim types

preserves

@@ -1 +1 @@
-Subproject commit 1cf0df255f0f18d2e07fe43943f114a66ddb89e9
+Subproject commit 5f746706b6e36534c579a09d693924058325adf1

src/syndicate/patterns.nim

@@ -1,18 +1,19 @@
 # SPDX-FileCopyrightText: ☭ 2021 Emery Hemingway
 # SPDX-License-Identifier: Unlicense
 
-import std/[macros, tables, typetraits]
+import std/[tables, typetraits]
+import preserves/private/macros
 
 import preserves
 import ./protocols/dataspacePatterns
 from ./actors import Ref
 
-export dataspacePatterns.`$`
+export dataspacePatterns.`$`, PatternKind, DCompoundKind
 
 type
-  AnyAtom = dataspacePatterns.AnyAtom[Ref]
+  AnyAtom* = dataspacePatterns.AnyAtom[Ref]
   DBind = dataspacePatterns.DBind[Ref]
-  DCompound* = dataspacePatterns.DCompound[Ref]
+  DCompound = dataspacePatterns.DCompound[Ref]
   DCompoundArr = dataspacePatterns.DCompoundArr[Ref]
   DCompoundDict = dataspacePatterns.DCompoundDict[Ref]
   DCompoundRec = dataspacePatterns.DCompoundRec[Ref]
@@ -74,40 +75,86 @@ proc `?`*(T: typedesc; bindings: sink openArray[(int, Pattern)]): Pattern =
   else:
     {.error: "no preserves pragma on " & $T.}
 
-proc `?`*(T: typedesc): Pattern =
+proc `?`*(T: static typedesc): Pattern =
   ## Derive a `Pattern` from type `T`.
   ## This works for `tuple` and `object` types but in the
   ## general case will return a wildcard binding.
-  when T.hasCustomPragma(preservesRecord):
+  when T is ref:
+    ?pointerBase(T)
+  elif T.hasCustomPragma(preservesRecord):
     var
       label = tosymbol(T.getCustomPragmaVal(preservesRecord), Ref)
       fields = newSeq[Pattern]()
-      dummy: ptr T
-    for key, val in fieldPairs(dummy[]):
-      fields.add grab()
+    for key, val in fieldPairs(default T):
+      fields.add ?(typeOf val)
     result = ?DCompound(
       orKind: DCompoundKind.rec,
       rec: DCompoundRec(
         label: label, fields: fields))
+  elif T.hasCustomPragma(preservesTuple):
+    var arr = DCompoundArr()
+    for key, val in fieldPairs(default T):
+      arr.items.add grab()
+    ?DCompound(
+      orKind: DCompoundKind.arr,
+      arr: arr)
+  elif T.hasCustomPragma(preservesDictionary):
+    var dict = DCompoundDict()
+    for key, val in fieldPairs(default T):
+      dict.entries[key.toSymbol(Ref)] = ?(typeOf val)
+    ?DCompound(
+      orKind: DCompoundKind.dict,
+      dict: dict)
   elif T is tuple:
-    var
-      arr = DCompoundArr()
-      dummy: ptr T
-    for key, val in fieldPairs(dummy[]):
+    var arr = DCompoundArr()
+    for key, val in fieldPairs(default T):
       arr.items.add ?(typeOf val)
     result = ?DCompound(
       orKind: DCompoundKind.arr,
       arr: arr)
   elif T is object:
-    var
-      dict = DCompoundDict()
-      dummy: ptr T
-    for key, val in fieldPairs(dummy[]):
-      dict.entries[key.toSymbol(Ref)] = grab() #?(typeOf val)
+    var dict = DCompoundDict()
+    for key, val in fieldPairs(default T):
+      dict.entries[key.toSymbol(Ref)] = ?(typeOf val)
     result = ?DCompound(
       orKind: DCompoundKind.dict,
       dict: dict)
-  elif T is ref:
-    ?pointerBase(T)
   else:
     grab() # capture any value
+
+type
+  Value = Preserve[Ref]
+  Path = seq[Value]
+  Analysis* = tuple
+    constPaths: seq[Path]
+    constValues: seq[Value]
+    capturePaths: seq[Path]
+
+func walk(result: var Analysis; path: var Path; p: Pattern)
+
+func walk(result: var Analysis; path: var Path; key: int|Value; pat: Pattern) =
+  path.add(key.toPreserve(Ref))
+  walk(result, path, pat)
+  discard path.pop
+
+func walk(result: var Analysis; path: var Path; p: Pattern) =
+  case p.orKind
+  of PatternKind.DCompound:
+    case p.dcompound.orKind
+    of DCompoundKind.rec:
+      for k, e in p.dcompound.rec.fields: walk(result, path, k, e)
+    of DCompoundKind.arr:
+       for k, e in p.dcompound.arr.items: walk(result, path, k, e)
+    of DCompoundKind.dict:
+      for k, e in p.dcompound.dict.entries: walk(result, path, k, e)
+  of PatternKind.DBind:
+    result.capturePaths.add(path)
+    walk(result, path, p.dbind.pattern)
+  of PatternKind.DDiscard: discard
+  of PatternKind.DLit:
+    result.constPaths.add(path)
+    result.constValues.add(p.dlit.value.toPreserve(Ref))
+
+func analyse*(p: Pattern): Analysis =
+  var path: Path
+  walk(result, path, p)