diff --git a/compiler/semcall.nim b/compiler/semcall.nim
index 9e9614796d..0880f5fdef 100644
--- a/compiler/semcall.nim
+++ b/compiler/semcall.nim
@@ -47,14 +47,14 @@ proc pickBestCandidate(c: PContext, headSymbol: PNode,
   var z: TCandidate
   
   if sym == nil: return
-  initCandidate(best, sym, initialBinding, symScope)
-  initCandidate(alt, sym, initialBinding, symScope)
+  initCandidate(c, best, sym, initialBinding, symScope)
+  initCandidate(c, alt, sym, initialBinding, symScope)
   best.state = csNoMatch
   
   while sym != nil:
     if sym.kind in filter:
       determineType(c, sym)
-      initCandidate(z, sym, initialBinding, o.lastOverloadScope)
+      initCandidate(c, z, sym, initialBinding, o.lastOverloadScope)
       z.calleeSym = sym
       matches(c, n, orig, z)
       if errors != nil:
@@ -199,15 +199,15 @@ proc instGenericConvertersSons*(c: PContext, n: PNode, x: TCandidate) =
 
 proc IndexTypesMatch(c: PContext, f, a: PType, arg: PNode): PNode = 
   var m: TCandidate
-  initCandidate(m, f)
-  result = paramTypesMatch(c, m, f, a, arg, nil)
+  initCandidate(c, m, f)
+  result = paramTypesMatch(m, f, a, arg, nil)
   if m.genericConverter and result != nil:
     instGenericConvertersArg(c, result, m)
 
 proc ConvertTo*(c: PContext, f: PType, n: PNode): PNode = 
   var m: TCandidate
-  initCandidate(m, f)
-  result = paramTypesMatch(c, m, f, n.typ, n, nil)
+  initCandidate(c, m, f)
+  result = paramTypesMatch(m, f, n.typ, n, nil)
   if m.genericConverter and result != nil:
     instGenericConvertersArg(c, result, m)
 
@@ -243,9 +243,9 @@ proc explicitGenericInstError(n: PNode): PNode =
   result = n
 
 proc explicitGenericSym(c: PContext, n: PNode, s: PSym): PNode =
-  var x: TCandidate
-  initCandidate(x, s, n)
-  var newInst = generateInstance(c, s, x.bindings, n.info)
+  var m: TCandidate
+  initCandidate(c, m, s, n)
+  var newInst = generateInstance(c, s, m.bindings, n.info)
   markUsed(n, s)
   result = newSymNode(newInst, n.info)
 
diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index a7fd1eaa08..67373c3032 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -142,7 +142,7 @@ proc checkConversionBetweenObjects(castDest, src: PType): TConvStatus =
 const 
   IntegralTypes = {tyBool, tyEnum, tyChar, tyInt..tyUInt64}
 
-proc checkConvertible(castDest, src: PType): TConvStatus =
+proc checkConvertible(c: PContext, castDest, src: PType): TConvStatus =
   result = convOK
   if sameType(castDest, src) and castDest.sym == src.sym:
     # don't annoy conversions that may be needed on another processor:
@@ -163,7 +163,7 @@ proc checkConvertible(castDest, src: PType): TConvStatus =
     # accept conversion between integral types
   else:
     # we use d, s here to speed up that operation a bit:
-    case cmpTypes(d, s)
+    case cmpTypes(c, d, s)
     of isNone, isGeneric:
       if not compareTypes(castDest, src, dcEqIgnoreDistinct):
         result = convNotLegal
@@ -202,7 +202,7 @@ proc semConv(c: PContext, n: PNode): PNode =
   var op = result.sons[1]
   
   if not isSymChoice(op):
-    let status = checkConvertible(result.typ, op.typ)
+    let status = checkConvertible(c, result.typ, op.typ)
     case status
     of convOK: nil
     of convNotNeedeed:
@@ -213,7 +213,7 @@ proc semConv(c: PContext, n: PNode): PNode =
   else:
     for i in countup(0, sonsLen(op) - 1):
       let it = op.sons[i]
-      let status = checkConvertible(result.typ, it.typ)
+      let status = checkConvertible(c, result.typ, it.typ)
       if status == convOK:
         markUsed(n, it.sym)
         markIndirect(c, it.sym)
@@ -324,15 +324,15 @@ proc isOpImpl(c: PContext, n: PNode): PNode =
     case t2.kind
     of tyTypeClasses:
       var m: TCandidate
-      InitCandidate(m, t2)
+      InitCandidate(c, m, t2)
       match = matchUserTypeClass(c, m, emptyNode, t2, t1) != nil
     of tyOrdinal:
       var m: TCandidate
-      InitCandidate(m, t2)
+      InitCandidate(c, m, t2)
       match = isOrdinalType(t1)
     of tySequence, tyArray, tySet:
       var m: TCandidate
-      InitCandidate(m, t2)
+      InitCandidate(c, m, t2)
       match = typeRel(m, t2, t1) != isNone
     else:
       match = sameType(t1, t2)
@@ -707,7 +707,7 @@ proc semIndirectOp(c: PContext, n: PNode, flags: TExprFlags): PNode =
   if t != nil and t.kind == tyProc:
     # This is a proc variable, apply normal overload resolution
     var m: TCandidate
-    initCandidate(m, t)
+    initCandidate(c, m, t)
     matches(c, n, nOrig, m)
     if m.state != csMatch:
       if c.inCompilesContext > 0:
diff --git a/compiler/semtypes.nim b/compiler/semtypes.nim
index 85928ee751..7e76e950b6 100644
--- a/compiler/semtypes.nim
+++ b/compiler/semtypes.nim
@@ -838,7 +838,7 @@ proc semGeneric(c: PContext, n: PNode, s: PSym, prev: PType): PType =
   else:
     internalAssert s.typ.kind == tyGenericBody
 
-    var m = newCandidate(s, n)
+    var m = newCandidate(c, s, n)
     matches(c, n, copyTree(n), m)
     
     if m.state != csMatch:
diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index 87f1decf48..42eefec5a2 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -21,7 +21,8 @@ type
   TCandidateState* = enum 
     csEmpty, csMatch, csNoMatch
 
-  TCandidate* {.final.} = object 
+  TCandidate* {.final.} = object
+    c*: PContext
     exactMatches*: int       # also misused to prefer iters over procs
     genericMatches: int      # also misused to prefer constraints
     subtypeMatches: int
@@ -58,7 +59,9 @@ const
     
 proc markUsed*(n: PNode, s: PSym)
 
-proc initCandidateAux(c: var TCandidate, callee: PType) {.inline.} = 
+proc initCandidateAux(ctx: PContext,
+                      c: var TCandidate, callee: PType) {.inline.} =
+  c.c = ctx
   c.exactMatches = 0
   c.subtypeMatches = 0
   c.convMatches = 0
@@ -71,17 +74,17 @@ proc initCandidateAux(c: var TCandidate, callee: PType) {.inline.} =
   c.genericConverter = false
   c.inheritancePenalty = 0
 
-proc initCandidate*(c: var TCandidate, callee: PType) = 
-  initCandidateAux(c, callee)
+proc initCandidate*(ctx: PContext, c: var TCandidate, callee: PType) =
+  initCandidateAux(ctx, c, callee)
   c.calleeSym = nil
   initIdTable(c.bindings)
 
 proc put(t: var TIdTable, key, val: PType) {.inline.} =
   IdTablePut(t, key, val)
 
-proc initCandidate*(c: var TCandidate, callee: PSym, binding: PNode, 
-                    calleeScope = -1) =
-  initCandidateAux(c, callee.typ)
+proc initCandidate*(ctx: PContext, c: var TCandidate, callee: PSym,
+                    binding: PNode, calleeScope = -1) =
+  initCandidateAux(ctx, c, callee.typ)
   c.calleeSym = callee
   c.calleeScope = calleeScope
   initIdTable(c.bindings)
@@ -93,10 +96,12 @@ proc initCandidate*(c: var TCandidate, callee: PSym, binding: PNode,
       #debug(formalTypeParam)
       put(c.bindings, formalTypeParam, binding[i].typ)
 
-proc newCandidate*(callee: PSym, binding: PNode, calleeScope = -1): TCandidate =
-  initCandidate(result, callee, binding, calleeScope)
+proc newCandidate*(ctx: PContext, callee: PSym,
+                   binding: PNode, calleeScope = -1): TCandidate =
+  initCandidate(ctx, result, callee, binding, calleeScope)
 
 proc copyCandidate(a: var TCandidate, b: TCandidate) = 
+  a.c = b.c
   a.exactMatches = b.exactMatches
   a.subtypeMatches = b.subtypeMatches
   a.convMatches = b.convMatches
@@ -762,10 +767,10 @@ proc typeRel(c: var TCandidate, f, a: PType, doBind = true): TTypeRelation =
     result = isEqual
   else: internalError("typeRel: " & $f.kind)
   
-proc cmpTypes*(f, a: PType): TTypeRelation = 
-  var c: TCandidate
-  InitCandidate(c, f)
-  result = typeRel(c, f, a)
+proc cmpTypes*(c: PContext, f, a: PType): TTypeRelation = 
+  var m: TCandidate
+  InitCandidate(c, m, f)
+  result = typeRel(m, f, a)
 
 proc getInstantiatedType(c: PContext, arg: PNode, m: TCandidate, 
                          f: PType): PType = 
@@ -887,13 +892,14 @@ proc matchUserTypeClass*(c: PContext, m: var TCandidate,
   result = arg
   put(m.bindings, f, a)
 
-proc ParamTypesMatchAux(c: PContext, m: var TCandidate, f, argType: PType,
+proc ParamTypesMatchAux(m: var TCandidate, f, argType: PType,
                         argSemantized, argOrig: PNode): PNode =
   var
     r: TTypeRelation
     arg = argSemantized
 
   let
+    c = m.c
     a0 = if c.InTypeClass > 0: argType.skipTypes({tyTypeDesc})
          else: argType
     a = if a0 != nil: a0.skipTypes({tyStatic}) else: a0
@@ -1007,19 +1013,20 @@ proc ParamTypesMatchAux(c: PContext, m: var TCandidate, f, argType: PType,
         else:
           result = userConvMatch(c, m, base(f), a, arg)
 
-proc ParamTypesMatch*(c: PContext, m: var TCandidate, f, a: PType, 
+proc ParamTypesMatch*(m: var TCandidate, f, a: PType,
                       arg, argOrig: PNode): PNode =
   if arg == nil or arg.kind notin nkSymChoices:
-    result = ParamTypesMatchAux(c, m, f, a, arg, argOrig)
+    result = ParamTypesMatchAux(m, f, a, arg, argOrig)
   else: 
     # CAUTION: The order depends on the used hashing scheme. Thus it is
     # incorrect to simply use the first fitting match. However, to implement
     # this correctly is inefficient. We have to copy `m` here to be able to
     # roll back the side effects of the unification algorithm.
+    let c = m.c
     var x, y, z: TCandidate
-    initCandidate(x, m.callee)
-    initCandidate(y, m.callee)
-    initCandidate(z, m.callee)
+    initCandidate(c, x, m.callee)
+    initCandidate(c, y, m.callee)
+    initCandidate(c, z, m.callee)
     x.calleeSym = m.calleeSym
     y.calleeSym = m.calleeSym
     z.calleeSym = m.calleeSym
@@ -1051,7 +1058,7 @@ proc ParamTypesMatch*(c: PContext, m: var TCandidate, f, a: PType,
     else: 
       # only one valid interpretation found:
       markUsed(arg, arg.sons[best].sym)
-      result = ParamTypesMatchAux(c, m, f, arg.sons[best].typ, arg.sons[best],
+      result = ParamTypesMatchAux(m, f, arg.sons[best].typ, arg.sons[best],
                                   argOrig)
 
 proc setSon(father: PNode, at: int, son: PNode) = 
@@ -1142,7 +1149,7 @@ proc matchesAux(c: PContext, n, nOrig: PNode,
       m.baseTypeMatch = false
       n.sons[a].sons[1] = prepareOperand(c, formal.typ, n.sons[a].sons[1])
       n.sons[a].typ = n.sons[a].sons[1].typ
-      var arg = ParamTypesMatch(c, m, formal.typ, n.sons[a].typ,
+      var arg = ParamTypesMatch(m, formal.typ, n.sons[a].typ,
                                 n.sons[a].sons[1], nOrig.sons[a].sons[1])
       if arg == nil:
         m.state = csNoMatch
@@ -1172,7 +1179,7 @@ proc matchesAux(c: PContext, n, nOrig: PNode,
         elif formal != nil:
           m.baseTypeMatch = false
           n.sons[a] = prepareOperand(c, formal.typ, n.sons[a])
-          var arg = ParamTypesMatch(c, m, formal.typ, n.sons[a].typ,
+          var arg = ParamTypesMatch(m, formal.typ, n.sons[a].typ,
                                     n.sons[a], nOrig.sons[a])
           if (arg != nil) and m.baseTypeMatch and (container != nil):
             addSon(container, arg)
@@ -1195,7 +1202,7 @@ proc matchesAux(c: PContext, n, nOrig: PNode,
           return 
         m.baseTypeMatch = false
         n.sons[a] = prepareOperand(c, formal.typ, n.sons[a])
-        var arg = ParamTypesMatch(c, m, formal.typ, n.sons[a].typ,
+        var arg = ParamTypesMatch(m, formal.typ, n.sons[a].typ,
                                   n.sons[a], nOrig.sons[a])
         if arg == nil:
           m.state = csNoMatch
@@ -1249,8 +1256,8 @@ proc matches*(c: PContext, n, nOrig: PNode, m: var TCandidate) =
 
 proc argtypeMatches*(c: PContext, f, a: PType): bool =
   var m: TCandidate
-  initCandidate(m, f)
-  let res = paramTypesMatch(c, m, f, a, ast.emptyNode, nil)
+  initCandidate(c, m, f)
+  let res = paramTypesMatch(m, f, a, ast.emptyNode, nil)
   #instantiateGenericConverters(c, res, m)
   # XXX this is used by patterns.nim too; I think it's better to not
   # instantiate generic converters for that
@@ -1312,7 +1319,7 @@ tests:
 
     setup:
       var c: TCandidate
-      InitCandidate(c, nil)
+      InitCandidate(nil, c, nil)
 
     template yes(x, y) =
       test astToStr(x) & " is " & astToStr(y):
diff --git a/compiler/suggest.nim b/compiler/suggest.nim
index 76a6c21d92..04a222db44 100644
--- a/compiler/suggest.nim
+++ b/compiler/suggest.nim
@@ -119,7 +119,7 @@ proc argsFit(c: PContext, candidate: PSym, n, nOrig: PNode): bool =
   case candidate.kind 
   of OverloadableSyms:
     var m: TCandidate
-    initCandidate(m, candidate, nil)
+    initCandidate(c, m, candidate, nil)
     sigmatch.partialMatch(c, n, nOrig, m)
     result = m.state != csNoMatch
   else: