first implementation of package level types that allow forwarding across module boundaries

compiler/ast.nim

@@ -1668,5 +1668,5 @@ template hasDestructor*(t: PType): bool = tfHasAsgn in t.flags
 template incompleteType*(t: PType): bool =
   t.sym != nil and {sfForward, sfNoForward} * t.sym.flags == {sfForward}
 
-template typeCompleted*(t: PType) =
+template typeCompleted*(s: PSym) =
-  incl t.sym.flags, sfNoForward
+  incl s.flags, sfNoForward

compiler/lookups.nim

@@ -155,7 +155,7 @@ proc ensureNoMissingOrUnusedSymbols(scope: PScope) =
   var s = initTabIter(it, scope.symbols)
   var missingImpls = 0
   while s != nil:
-    if sfForward in s.flags:
+    if sfForward in s.flags and s.kind != skType:
       # too many 'implementation of X' errors are annoying
       # and slow 'suggest' down:
       if missingImpls == 0:

compiler/pragmas.nim

@@ -55,7 +55,7 @@ const
     wPure, wHeader, wCompilerproc, wFinal, wSize, wExtern, wShallow,
     wImportCpp, wImportObjC, wError, wIncompleteStruct, wByCopy, wByRef,
     wInheritable, wGensym, wInject, wRequiresInit, wUnchecked, wUnion, wPacked,
-    wBorrow, wGcSafe, wExportNims, wPartial, wUsed, wExplain, wForward}
+    wBorrow, wGcSafe, wExportNims, wPartial, wUsed, wExplain, wPackage}
   fieldPragmas* = {wImportc, wExportc, wDeprecated, wExtern,
     wImportCpp, wImportObjC, wError, wGuard, wBitsize, wUsed}
   varPragmas* = {wImportc, wExportc, wVolatile, wRegister, wThreadVar, wNodecl,
@@ -799,7 +799,7 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: int,
         noVal(it)
         if sym.typ == nil or tfFinal in sym.typ.flags: invalidPragma(it)
         else: incl(sym.typ.flags, tfInheritable)
-      of wForward:
+      of wPackage:
         noVal(it)
         if sym.typ == nil: invalidPragma(it)
         else: incl(sym.flags, sfForward)

compiler/semstmts.nim

@@ -775,21 +775,52 @@ proc typeSectionLeftSidePass(c: PContext, n: PNode) =
     checkSonsLen(a, 3)
     let name = a.sons[0]
     var s: PSym
-    if name.kind == nkDotExpr:
+    if name.kind == nkDotExpr and a[2].kind == nkObjectTy:
-      s = qualifiedLookUp(c, name, {checkUndeclared, checkModule})
+      let pkgName = considerQuotedIdent(name[0])
-      if s.kind != skType or
+      let typName = considerQuotedIdent(name[1])
-         s.typ.skipTypes(abstractPtrs).kind != tyObject or
+      let pkg = c.graph.packageSyms.strTableGet(pkgName)
-         tfPartial notin s.typ.skipTypes(abstractPtrs).flags:
+      if pkg.isNil or pkg.kind != skPackage:
-        localError(name.info, "only .partial objects can be extended")
+        localError(name.info, "unknown package name: " & pkgName.s)
+      else:
+        let typsym = pkg.tab.strTableGet(typName)
+        if typsym.isNil:
+          s = semIdentDef(c, name[1], skType)
+          s.typ = newTypeS(tyObject, c)
+          s.typ.sym = s
+          s.flags.incl sfForward
+          pkg.tab.strTableAdd s
+          addInterfaceDecl(c, s)
+        elif typsym.kind == skType and sfForward in typsym.flags:
+          s = typsym
+          addInterfaceDecl(c, s)
+        else:
+          localError(name.info, typsym.name.s & " is not a type that can be forwarded")
+          s = typsym
+      when false:
+        s = qualifiedLookUp(c, name, {checkUndeclared, checkModule})
+        if s.kind != skType or
+          s.typ.skipTypes(abstractPtrs).kind != tyObject or
+          tfPartial notin s.typ.skipTypes(abstractPtrs).flags:
+          localError(name.info, "only .partial objects can be extended")
     else:
       s = semIdentDef(c, name, skType)
       s.typ = newTypeS(tyForward, c)
       s.typ.sym = s             # process pragmas:
       if name.kind == nkPragmaExpr:
         pragma(c, s, name.sons[1], typePragmas)
-        if sfForward in s.flags: strTableAdd(c.graph.forwardedTypes, s)
+      if sfForward in s.flags:
+        # check if the symbol already exists:
+        let pkg = c.module.owner
+        if not isTopLevel(c) or pkg.isNil:
+          localError(name.info, "only top level types in a package can be 'forward'")
+        else:
+          let typsym = pkg.tab.strTableGet(s.name)
+          if typsym != nil:
+            typeCompleted(typsym)
+            s = typsym
       # add it here, so that recursive types are possible:
       if sfGenSym notin s.flags: addInterfaceDecl(c, s)
+
     a.sons[0] = newSymNode(s)
 
 proc checkCovariantParamsUsages(genericType: PType) =

compiler/wordrecg.nim

@@ -55,7 +55,7 @@ type
     wFloatchecks, wNanChecks, wInfChecks,
     wAssertions, wPatterns, wWarnings,
     wHints, wOptimization, wRaises, wWrites, wReads, wSize, wEffects, wTags,
-    wDeadCodeElim, wSafecode, wForward, wNoForward, wReorder, wNoRewrite,
+    wDeadCodeElim, wSafecode, wPackage, wNoForward, wReorder, wNoRewrite,
     wPragma,
     wCompileTime, wNoInit,
     wPassc, wPassl, wBorrow, wDiscardable,
@@ -143,7 +143,7 @@ const
 
     "assertions", "patterns", "warnings", "hints",
     "optimization", "raises", "writes", "reads", "size", "effects", "tags",
-    "deadcodeelim", "safecode", "forward", "noforward", "reorder", "norewrite",
+    "deadcodeelim", "safecode", "package", "noforward", "reorder", "norewrite",
     "pragma",
     "compiletime", "noinit",
     "passc", "passl", "borrow", "discardable", "fieldchecks",

tests/misc/tupcomingfeatures.nim

@@ -6,12 +6,8 @@ discard """
 {.this: self.}
 
 type
-  Foo {.partial.} = object
+  Foo = object
-    a, b: int
+    a, b, x: int
-
-type
-  tupcomingfeatures.Foo = object
-    x: int
 
 proc yay(self: Foo) =
   echo a, " ", b, " ", x

todo.txt

@@ -23,7 +23,6 @@ Not critical for 1.0
 - make '--implicitStatic:on' the default; then we can also clean up the
   'static[T]' mess in the compiler!
 - ``not`` or ``~`` for the effects system
-- document and stress test ``.partial`` object declarations
 - figure out why C++ bootstrapping is so much slower
 - The bitwise 'not' operator cold be renamed to 'bnot' to
   prevent 'not 4 == 5' from compiling. -> requires 'mixin' annotation for procs!