generic multi-methods should work now

compiler/ast.nim

@@ -850,6 +850,7 @@ type
                               # see instantiateDestructor in semdestruct.nim
     deepCopy*: PSym           # overriden 'deepCopy' operation
     assignment*: PSym         # overriden '=' operator
+    methods*: seq[(int,PSym)] # attached methods
     size*: BiggestInt         # the size of the type in bytes
                               # -1 means that the size is unkwown
     align*: int16             # the type's alignment requirements

compiler/cgmeth.nim

@@ -63,7 +63,7 @@ proc sameMethodBucket(a, b: PSym): MethodResult =
     while true:
       aa = skipTypes(aa, {tyGenericInst})
       bb = skipTypes(bb, {tyGenericInst})
-      if (aa.kind == bb.kind) and (aa.kind in {tyVar, tyPtr, tyRef}):
+      if aa.kind == bb.kind and aa.kind in {tyVar, tyPtr, tyRef}:
         aa = aa.lastSon
         bb = bb.lastSon
       else:
@@ -187,7 +187,7 @@ proc cmpSignatures(a, b: PSym, relevantCols: IntSet): int =
       var aa = skipTypes(a.typ.sons[col], skipPtrs)
       var bb = skipTypes(b.typ.sons[col], skipPtrs)
       var d = inheritanceDiff(aa, bb)
-      if (d != high(int)):
+      if (d != high(int)) and d != 0:
         return d
 
 proc sortBucket(a: var TSymSeq, relevantCols: IntSet) =

compiler/semdata.nim

@@ -104,7 +104,7 @@ type
     hloLoopDetector*: int     # used to prevent endless loops in the HLO
     inParallelStmt*: int
     instTypeBoundOp*: proc (c: PContext; dc: PSym; t: PType; info: TLineInfo;
-                            op: TTypeAttachedOp): PSym {.nimcall.}
+                            op: TTypeAttachedOp; col: int): PSym {.nimcall.}
     selfName*: PIdent
     signatures*: TStrTable
 

compiler/semstmts.nim

@@ -1352,7 +1352,19 @@ proc semMethod(c: PContext, n: PNode): PNode =
   # macros can transform methods to nothing:
   if namePos >= result.safeLen: return result
   var s = result.sons[namePos].sym
-  if not isGenericRoutine(s):
+  if isGenericRoutine(s):
+    let tt = s.typ
+    var foundObj = false
+    for col in countup(0, sonsLen(tt)-1):
+      let t = tt.sons[col]
+      if t != nil and t.kind == tyGenericInvocation:
+        var x = skipTypes(t.sons[0], {tyVar, tyPtr, tyRef, tyGenericInst, tyGenericInvocation, tyGenericBody})
+        if x.kind == tyObject:
+          foundObj = true
+          x.methods.safeAdd((col,s))
+    if not foundObj:
+      message(n.info, warnDeprecated, "generic method not attachable to object type")
+  else:
     # why check for the body? bug #2400 has none. Checking for sfForward makes
     # no sense either.
     # and result.sons[bodyPos].kind != nkEmpty:

compiler/semtypinst.nim

@@ -289,7 +289,8 @@ proc handleGenericInvocation(cl: var TReplTypeVars, t: PType): PType =
     # but we already raised an error!
     rawAddSon(result, header.sons[i])
 
-  var newbody = replaceTypeVarsT(cl, lastSon(body))
+  let bbody = lastSon body
+  var newbody = replaceTypeVarsT(cl, bbody)
   cl.skipTypedesc = oldSkipTypedesc
   newbody.flags = newbody.flags + (t.flags + body.flags - tfInstClearedFlags)
   result.flags = result.flags + newbody.flags - tfInstClearedFlags
@@ -306,12 +307,18 @@ proc handleGenericInvocation(cl: var TReplTypeVars, t: PType): PType =
     # 'deepCopy' needs to be instantiated for
     # generics *when the type is constructed*:
     newbody.deepCopy = cl.c.instTypeBoundOp(cl.c, dc, result, cl.info,
-                                            attachedDeepCopy)
+                                            attachedDeepCopy, 1)
   let asgn = newbody.assignment
   if asgn != nil and sfFromGeneric notin asgn.flags:
     # '=' needs to be instantiated for generics when the type is constructed:
     newbody.assignment = cl.c.instTypeBoundOp(cl.c, asgn, result, cl.info,
-                                              attachedAsgn)
+                                              attachedAsgn, 1)
+  let methods = skipTypes(bbody, abstractPtrs).methods
+  for col, meth in items(methods):
+    # we instantiate the known methods belonging to that type, this causes
+    # them to be registered and that's enough, so we 'discard' the result.
+    discard cl.c.instTypeBoundOp(cl.c, meth, result, cl.info,
+      attachedAsgn, col)
 
 proc eraseVoidParams*(t: PType) =
   # transform '(): void' into '()' because old parts of the compiler really

compiler/sigmatch.nim

@@ -1796,16 +1796,19 @@ proc argtypeMatches*(c: PContext, f, a: PType): bool =
   result = res != nil
 
 proc instTypeBoundOp*(c: PContext; dc: PSym; t: PType; info: TLineInfo;
-                      op: TTypeAttachedOp): PSym {.procvar.} =
+                      op: TTypeAttachedOp; col: int): PSym {.procvar.} =
   var m: TCandidate
   initCandidate(c, m, dc.typ)
-  var f = dc.typ.sons[1]
+  if col >= dc.typ.len:
+    localError(info, errGenerated, "cannot instantiate '" & dc.name.s & "'")
+    return nil
+  var f = dc.typ.sons[col]
   if op == attachedDeepCopy:
     if f.kind in {tyRef, tyPtr}: f = f.lastSon
   else:
     if f.kind == tyVar: f = f.lastSon
   if typeRel(m, f, t) == isNone:
-    localError(info, errGenerated, "cannot instantiate 'deepCopy'")
+    localError(info, errGenerated, "cannot instantiate '" & dc.name.s & "'")
   else:
     result = c.semGenerateInstance(c, dc, m.bindings, info)
     assert sfFromGeneric in result.flags