diff --git a/compiler/procfind.nim b/compiler/procfind.nim
index fde4d22ea8..4a1fb5ac8c 100755
--- a/compiler/procfind.nim
+++ b/compiler/procfind.nim
@@ -29,7 +29,7 @@ proc equalGenericParams(procA, procB: PNode): bool =
     a = procA.sons[i].sym
     b = procB.sons[i].sym
     if (a.name.id != b.name.id) or 
-        not sameTypeOrNil(a.typ, b.typ, {TypeDescExactMatch}): return 
+        not sameTypeOrNil(a.typ, b.typ, {TypeDescExactMatch}): return
     if (a.ast != nil) and (b.ast != nil): 
       if not ExprStructuralEquivalent(a.ast, b.ast): return 
   result = true
@@ -44,7 +44,7 @@ proc SearchForProc*(c: PContext, fn: PSym, tos: int): PSym =
       if equalGenericParams(result.ast.sons[genericParamsPos], 
                             fn.ast.sons[genericParamsPos]): 
         case equalParams(result.typ.n, fn.typ.n)
-        of paramsEqual: 
+        of paramsEqual:
           return 
         of paramsIncompatible: 
           LocalError(fn.info, errNotOverloadable, fn.name.s)
diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index c48434eb78..1f2511694c 100755
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -12,18 +12,18 @@
 
 import 
   intsets, ast, astalgo, semdata, types, msgs, renderer, lookups, semtypinst,
-  magicsys, condsyms, idents, lexer, options
+  magicsys, condsyms, idents, lexer, options, parampatterns
 
 type
   TCandidateState* = enum 
     csEmpty, csMatch, csNoMatch
 
   TCandidate* {.final.} = object 
-    exactMatches*: int
+    exactMatches*: int       # also misused to prefer iters over procs
+    genericMatches: int      # also misused to prefer constraints
     subtypeMatches: int
     intConvMatches: int      # conversions to int are not as expensive
     convMatches: int
-    genericMatches: int
     state*: TCandidateState
     callee*: PType           # may not be nil!
     calleeSym*: PSym         # may be nil
@@ -773,6 +773,15 @@ proc setSon(father: PNode, at: int, son: PNode) =
 
 proc matchesAux*(c: PContext, n, nOrig: PNode,
                  m: var TCandidate, marker: var TIntSet) = 
+  template checkConstraint(n: expr) {.immediate, dirty.} =
+    if not formal.constraint.isNil:
+      if matchNodeKinds(formal.constraint, n):
+        # better match over other routines with no such restriction:
+        inc(m.genericMatches, 100)
+      else:
+        m.state = csNoMatch
+        return
+  
   var f = 1 # iterates over formal parameters
   var a = 1 # iterates over the actual given arguments
   m.state = csMatch           # until proven otherwise
@@ -805,7 +814,8 @@ proc matchesAux*(c: PContext, n, nOrig: PNode,
                                 n.sons[a].sons[1], nOrig.sons[a].sons[1])
       if arg == nil: 
         m.state = csNoMatch
-        return 
+        return
+      checkConstraint(n.sons[a].sons[1])
       if m.baseTypeMatch: 
         assert(container == nil)
         container = newNodeI(nkBracket, n.sons[a].info)
@@ -862,6 +872,7 @@ proc matchesAux*(c: PContext, n, nOrig: PNode,
           if f != formalLen - 1: container = nil
         else: 
           setSon(m.call, formal.position + 1, arg)
+      checkConstraint(n.sons[a])
     inc(a)
     inc(f)
 
diff --git a/compiler/types.nim b/compiler/types.nim
index 825b1027a0..23d202fdf4 100755
--- a/compiler/types.nim
+++ b/compiler/types.nim
@@ -632,7 +632,8 @@ proc SameTypeOrNil*(a, b: PType, flags: TTypeCmpFlags = {}): bool =
       result = SameTypeAux(a, b, c)
 
 proc equalParam(a, b: PSym): TParamsEquality = 
-  if SameTypeOrNil(a.typ, b.typ, {TypeDescExactMatch}): 
+  if SameTypeOrNil(a.typ, b.typ, {TypeDescExactMatch}) and
+      ExprStructuralEquivalent(a.constraint, b.constraint):
     if a.ast == b.ast: 
       result = paramsEqual
     elif a.ast != nil and b.ast != nil: 
diff --git a/tests/run/tastoverload1.nim b/tests/run/tastoverload1.nim
new file mode 100644
index 0000000000..c8705547af
--- /dev/null
+++ b/tests/run/tastoverload1.nim
@@ -0,0 +1,21 @@
+discard """
+  output: '''string literal
+no string literal
+no string literal'''
+"""
+
+proc optLit(a: string{lit}) =
+  echo "string literal"
+
+proc optLit(a: string) =
+  echo "no string literal"
+
+const
+  constant = "abc"
+
+var
+  variable = "xyz"
+
+optLit("literal")
+optLit(constant)
+optLit(variable)
diff --git a/todo.txt b/todo.txt
index 870265ac3b..c5b5eb4e7f 100755
--- a/todo.txt
+++ b/todo.txt
@@ -6,6 +6,7 @@ version 0.9.2
     overloading
   - ``hoist`` pragma for loop hoisting: can be easily done with 
     AST overloading + global
+  - document overloading based on ASTs
 
 - test&finish first class iterators:
   * nested iterators