implemented 'borrow dot' feature for distinct types

compiler/ast.nim

@@ -424,7 +424,7 @@ type
     nfIsRef     # this node is a 'ref' node; used for the VM
  
   TNodeFlags* = set[TNodeFlag]
-  TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: 23)
+  TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: 28)
     tfVarargs,        # procedure has C styled varargs
     tfNoSideEffect,   # procedure type does not allow side effects
     tfFinal,          # is the object final?
@@ -464,6 +464,8 @@ type
                       # T and I here can bind to both typedesc and static types
                       # before this is determined, we'll consider them to be a
                       # wildcard type.
+    tfGuarded         # guarded pointer
+    tfBorrowDot       # distinct type borrows '.'
 
   TTypeFlags* = set[TTypeFlag]
 

compiler/pragmas.nim

@@ -52,7 +52,8 @@ const
   typePragmas* = {wImportc, wExportc, wDeprecated, wMagic, wAcyclic, wNodecl, 
     wPure, wHeader, wCompilerproc, wFinal, wSize, wExtern, wShallow,
     wImportCpp, wImportObjC, wError, wIncompleteStruct, wByCopy, wByRef,
-    wInheritable, wGensym, wInject, wRequiresInit, wUnchecked, wUnion, wPacked}
+    wInheritable, wGensym, wInject, wRequiresInit, wUnchecked, wUnion, wPacked,
+    wBorrow}
   fieldPragmas* = {wImportc, wExportc, wDeprecated, wExtern, 
     wImportCpp, wImportObjC, wError}
   varPragmas* = {wImportc, wExportc, wVolatile, wRegister, wThreadVar, wNodecl, 
@@ -511,6 +512,13 @@ proc pragmaRaisesOrTags(c: PContext, n: PNode) =
   else:
     invalidPragma(n)
 
+proc typeBorrow(sym: PSym, n: PNode) =
+  if n.kind == nkExprColonExpr:
+    let it = n.sons[1]
+    if it.kind != nkAccQuoted:
+      localError(n.info, "a type can only borrow `.` for now")
+  incl(sym.typ.flags, tfBorrowDot)
+
 proc singlePragma(c: PContext, sym: PSym, n: PNode, i: int,
                   validPragmas: TSpecialWords): bool =
   var it = n.sons[i]
@@ -631,9 +639,12 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: int,
           noVal(it)
           if sym.typ == nil: invalidPragma(it)
           else: incl(sym.typ.flags, tfVarargs)
-        of wBorrow: 
-          noVal(it)
-          incl(sym.flags, sfBorrow)
+        of wBorrow:
+          if sym.kind == skType:
+            typeBorrow(sym, it)
+          else:
+            noVal(it)
+            incl(sym.flags, sfBorrow)
         of wFinal: 
           noVal(it)
           if sym.typ == nil: invalidPragma(it)

compiler/semexprs.nim

@@ -1001,15 +1001,15 @@ proc builtinFieldAccess(c: PContext, n: PNode, flags: TExprFlags): PNode =
     # reset to prevent 'nil' bug: see "tests/reject/tenumitems.nim":
     ty = n.sons[0].typ
     return nil
-    
   ty = skipTypes(ty, {tyGenericInst, tyVar, tyPtr, tyRef})
+  while tfBorrowDot in ty.flags: ty = ty.skipTypes({tyDistinct})
   var check: PNode = nil
-  if ty.kind == tyObject: 
-    while true: 
+  if ty.kind == tyObject:
+    while true:
       check = nil
       f = lookupInRecordAndBuildCheck(c, n, ty.n, i, check)
-      if f != nil: break 
-      if ty.sons[0] == nil: break 
+      if f != nil: break
+      if ty.sons[0] == nil: break
       ty = skipTypes(ty.sons[0], {tyGenericInst})
     if f != nil:
       if fieldVisible(c, f):