cleanup of in/out covariance handling

compiler/ast.nim

@@ -212,8 +212,6 @@ type
     nkIteratorTy,         # iterator type
     nkSharedTy,           # 'shared T'
                           # we use 'nkPostFix' for the 'not nil' addition
-    nkInTy,               # prefix `in` used to mark contravariant types
-    nkOutTy,              # prefix `out` used to mark covariant types
     nkEnumTy,             # enum body
     nkEnumFieldDef,       # `ident = expr` in an enumeration
     nkArgList,            # argument list
@@ -226,7 +224,7 @@ type
   TNodeKinds* = set[TNodeKind]
 
 type
-  TSymFlag* = enum    # already 32 flags!
+  TSymFlag* = enum    # already 33 flags!
     sfUsed,           # read access of sym (for warnings) or simply used
     sfExported,       # symbol is exported from module
     sfFromGeneric,    # symbol is instantiation of a generic; this is needed
@@ -270,9 +268,6 @@ type
     sfDiscardable,    # returned value may be discarded implicitly
     sfOverriden,      # proc is overriden
     sfGenSym          # symbol is 'gensym'ed; do not add to symbol table
-    sfCovariant       # covariant generic param mimicing a ptr type
-    sfWeakCovariant   # covariant generic param mimicing a seq/array type
-    sfContravariant   # contravariant generic param
 
   TSymFlags* = set[TSymFlag]
 
@@ -460,7 +455,7 @@ type
     nfBlockArg  # this a stmtlist appearing in a call (e.g. a do block)
 
   TNodeFlags* = set[TNodeFlag]
-  TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: 30)
+  TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: beyond that)
     tfVarargs,        # procedure has C styled varargs
                       # tyArray type represeting a varargs list
     tfNoSideEffect,   # procedure type does not allow side effects
@@ -513,6 +508,9 @@ type
     tfTriggersCompileTime # uses the NimNode type which make the proc
                           # implicitly '.compiletime'
     tfRefsAnonObj     # used for 'ref object' and 'ptr object'
+    tfCovariant       # covariant generic param mimicing a ptr type
+    tfWeakCovariant   # covariant generic param mimicing a seq/array type
+    tfContravariant   # contravariant generic param
 
   TTypeFlags* = set[TTypeFlag]
 

compiler/parser.nim

@@ -1521,9 +1521,9 @@ proc parseGenericParam(p: var TParser): PNode =
   while true:
     case p.tok.tokType
     of tkIn, tkOut:
-      let kind = if p.tok.tokType == tkIn: nkInTy
-                 else: nkOutTy
-      a = newNodeP(kind, p)
+      let x = p.lex.cache.getIdent(if p.tok.tokType == tkIn: "in" else: "out")
+      a = newNodeP(nkPrefix, p)
+      a.addSon newIdentNodeP(x, p)
       getTok(p)
       expectIdent(p)
       a.addSon(parseSymbol(p))

compiler/semstmts.nim

@@ -758,7 +758,7 @@ proc checkCovariantParamsUsages(genericType: PType) =
 
     case t.kind
     of tyGenericParam:
-      t.sym.flags.incl sfWeakCovariant
+      t.flags.incl tfWeakCovariant
       return true
 
     of tyObject:
@@ -783,17 +783,17 @@ proc checkCovariantParamsUsages(genericType: PType) =
       for i in 1 .. <t.len:
         let param = t[i]
         if param.kind == tyGenericParam:
-          if sfCovariant in param.sym.flags:
-            let formalFlags = targetBody[i-1].sym.flags
-            if sfCovariant notin formalFlags:
+          if tfCovariant in param.flags:
+            let formalFlags = targetBody[i-1].flags
+            if tfCovariant notin formalFlags:
               error("covariant param '" & param.sym.name.s &
                     "' used in a non-covariant position")
-            elif sfWeakCovariant in formalFlags:
-              param.sym.flags.incl sfWeakCovariant
+            elif tfWeakCovariant in formalFlags:
+              param.flags.incl tfWeakCovariant
             result = true
-          elif sfContravariant in param.sym.flags:
+          elif tfContravariant in param.flags:
             let formalParam = targetBody[i-1].sym
-            if sfContravariant notin formalParam.flags:
+            if tfContravariant notin formalParam.typ.flags:
               error("contravariant param '" & param.sym.name.s &
                     "' used in a non-contravariant position")
             result = true
@@ -865,7 +865,7 @@ proc typeSectionRightSidePass(c: PContext, n: PNode) =
         body.sym = s
         body.size = -1 # could not be computed properly
         s.typ.sons[sonsLen(s.typ) - 1] = body
-        if sfCovariant in s.flags:
+        if tfCovariant in s.typ.flags:
           checkCovariantParamsUsages(s.typ)
           # XXX: This is a temporary limitation:
           # The codegen currently produces various failures with

compiler/semtypes.nim

@@ -1585,24 +1585,23 @@ proc semGenericParamList(c: PContext, n: PNode, father: PType = nil): PNode =
                       # of the parameter will be stored in the
                       # attached symbol.
       var paramName = a.sons[j]
-      var covarianceFlag = sfPure
+      var covarianceFlag = tfUnresolved
 
-      if paramName.kind in {nkInTy, nkOutTy}:
-        if not nimEnableCovariance or paramName.kind == nkInTy:
+      if paramName.safeLen == 2:
+        if not nimEnableCovariance or paramName[0].ident.s == "in":
           if father == nil or sfImportc notin father.sym.flags:
-            localError(paramName.info, errInOutFlagNotExtern,
-                       if paramName.kind == nkInTy: "in" else: "out")
-        covarianceFlag = if paramName.kind == nkInTy: sfContravariant
-                         else: sfCovariant
-        if father != nil: father.sym.flags.incl sfCovariant
-        paramName = paramName[0]
+            localError(paramName.info, errInOutFlagNotExtern, paramName[0].ident.s)
+        covarianceFlag = if paramName[0].ident.s == "in": tfContravariant
+                         else: tfCovariant
+        if father != nil: father.flags.incl tfCovariant
+        paramName = paramName[1]
 
       var s = if finalType.kind == tyStatic or tfWildcard in typ.flags:
           newSymG(skGenericParam, paramName, c).linkTo(finalType)
         else:
           newSymG(skType, paramName, c).linkTo(finalType)
 
-      if covarianceFlag != sfPure: s.flags.incl(covarianceFlag)
+      if covarianceFlag != tfUnresolved: s.typ.flags.incl(covarianceFlag)
       if def.kind != nkEmpty: s.ast = def
       if father != nil: addSonSkipIntLit(father, s.typ)
       s.position = result.len

compiler/sigmatch.nim

@@ -883,7 +883,7 @@ proc isCovariantPtr(c: var TCandidate, f, a: PType): bool =
     let body = f.base
     return body == a.base and
            a.sonsLen == 3 and
-           sfWeakCovariant notin body.sons[0].sym.flags and
+           tfWeakCovariant notin body.sons[0].flags and
            baseTypesCheck(f.sons[1], a.sons[1])
   else:
     return false
@@ -1302,22 +1302,22 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
           result = typeRel(c, ff, aa, nextFlags)
           if result notin {isEqual, isGeneric}:
             if trNoCovariance notin flags and ff.kind == aa.kind:
-              let paramFlags = rootf.base.sons[i-1].sym.flags
+              let paramFlags = rootf.base.sons[i-1].flags
               hasCovariance =
-                if sfCovariant in paramFlags:
-                  if sfWeakCovariant in paramFlags:
+                if tfCovariant in paramFlags:
+                  if tfWeakCovariant in paramFlags:
                     isCovariantPtr(c, ff, aa)
                   else:
                     ff.kind notin {tyRef, tyPtr} and result == isSubtype
                 else:
-                  sfContravariant in paramFlags and
+                  tfContravariant in paramFlags and
                     typeRel(c, aa, ff) == isSubtype
               if hasCovariance:
                 continue
 
             return isNone
         if prev == nil: put(c, f, a)
-        result = if hasCovariance: isGeneric else: isGeneric
+        result = isGeneric
       else:
         let fKind = rootf.lastSon.kind
         if fKind in {tyAnd, tyOr}:

lib/core/macros.nim

@@ -68,8 +68,6 @@ type
     nnkProcTy,
     nnkIteratorTy,         # iterator type
     nnkSharedTy,           # 'shared T'
-    nnkInTy,
-    nnkOutTy,
     nnkEnumTy,
     nnkEnumFieldDef,
     nnkArglist, nnkPattern