reference implementation of a vector swizzle library

This also provides the initial steps towards support for type class "filtered" type inference
fixes an "ordinal type expected" ICE, related to the use of static params

compiler/sigmatch.nim

@@ -40,6 +40,8 @@ type
     proxyMatch*: bool        # to prevent instantiations
     genericConverter*: bool  # true if a generic converter needs to
                              # be instantiated
+    coerceDistincts*: bool   # this is an explicit coercion that can strip away
+                             # a distrinct type
     typedescMatched: bool
     inheritancePenalty: int  # to prefer closest father object type
     errors*: seq[string]     # additional clarifications to be displayed to the
@@ -114,6 +116,9 @@ proc newCandidate*(ctx: PContext, callee: PSym,
                    binding: PNode, calleeScope = -1): TCandidate =
   initCandidate(ctx, result, callee, binding, calleeScope)
 
+proc newCandidate*(ctx: PContext, callee: PType): TCandidate =
+  initCandidate(ctx, result, callee)
+
 proc copyCandidate(a: var TCandidate, b: TCandidate) = 
   a.c = b.c
   a.exactMatches = b.exactMatches
@@ -460,7 +465,8 @@ proc matchUserTypeClass*(c: PContext, m: var TCandidate,
     
     if param.kind == nkVarTy:
       dummyName = param[0]
-      dummyType = makeVarType(c, a)
+      dummyType = if a.kind != tyVar: makeVarType(c, a)
+                  else: a
     else:
       dummyName = param
       dummyType = a
@@ -470,7 +476,7 @@ proc matchUserTypeClass*(c: PContext, m: var TCandidate,
     dummyParam.typ = dummyType
     addDecl(c, dummyParam)
 
-  var checkedBody = c.semTryExpr(c, copyTree(body.n[3]), bufferErrors = false)
+  var checkedBody = c.semTryExpr(c, body.n[3].copyTree, bufferErrors = false)
   m.errors = bufferedMsgs
   clearBufferedMsgs()
   if checkedBody == nil: return isNone
@@ -623,6 +629,20 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
       result = typeRel(c, f.sons[1], a.sons[1])
       if result < isGeneric:
         result = isNone
+      elif tfUnresolved in fRange.flags and
+           rangeHasStaticIf(fRange):
+        # This is a range from an array instantiated with a generic
+        # static param. We must extract the static param here and bind
+        # it to the size of the currently supplied array.
+        var
+          rangeStaticT = fRange.getStaticTypeFromRange
+          replacementT = newTypeWithSons(c.c, tyStatic, @[tyInt.getSysType])
+          inputUpperBound = a.sons[0].n[1].intVal
+        # we must correct for the off-by-one discrepancy between
+        # ranges and static params:
+        replacementT.n = newIntNode(nkIntLit, inputUpperBound + 1)
+        put(c.bindings, rangeStaticT, replacementT)
+        result = isGeneric
       elif lengthOrd(fRange) != lengthOrd(a):
         result = isNone
     else: discard
@@ -686,6 +706,7 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
           result = isSubtype
   of tyDistinct:
     if (a.kind == tyDistinct) and sameDistinctTypes(f, a): result = isEqual
+    elif c.coerceDistincts: result = typeRel(c, f.base, a)
   of tySet: 
     if a.kind == tySet: 
       if (f.sons[0].kind != tyGenericParam) and (a.sons[0].kind == tyEmpty): 
@@ -848,7 +869,7 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
 
   of tyUserTypeClass, tyUserTypeClassInst:
     considerPreviousT:
-      result = matchUserTypeClass(c.c, c, f, a)
+      result = matchUserTypeClass(c.c, c, f, aOrig)
       if result == isGeneric:
         put(c.bindings, f, a)
 
@@ -863,7 +884,7 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
   of tyGenericParam:
     var x = PType(idTableGet(c.bindings, f))
     if x == nil:
-      if c.calleeSym != nil and c.calleeSym.kind == skType and
+      if c.calleeSym != nil and c.callee.kind == tyGenericBody and
          f.kind == tyGenericParam and not c.typedescMatched:
         # XXX: The fact that generic types currently use tyGenericParam for 
         # their parameters is really a misnomer. tyGenericParam means "match
@@ -1051,7 +1072,7 @@ proc paramTypesMatchAux(m: var TCandidate, f, argType: PType,
     # XXX: When implicit statics are the default
     # this will be done earlier - we just have to
     # make sure that static types enter here
-    
+     
     # XXX: weaken tyGenericParam and call it tyGenericPlaceholder
     # and finally start using tyTypedesc for generic types properly.
     if argType.kind == tyGenericParam and tfWildcard in argType.flags:
@@ -1060,7 +1081,7 @@ proc paramTypesMatchAux(m: var TCandidate, f, argType: PType,
       return argSemantized
 
     if argType.kind == tyStatic:
-      if m.calleeSym.kind == skType:
+      if m.callee.kind == tyGenericBody:
         result = newNodeI(nkType, argOrig.info)
         result.typ = makeTypeFromExpr(c, arg)
         return