implemented generic multi methods

tests/run/tmultim6.nim

@@ -0,0 +1,30 @@
+discard """
+  output: "collide: unit, thing | collide: unit, thing | collide: thing, unit"
+"""
+# Test multi methods
+
+type
+  TThing = object {.inheritable.}
+  TUnit[T] = object of TThing
+    x: T
+  TParticle = object of TThing
+    a, b: int
+    
+method collide(a, b: TThing) {.inline.} =
+  quit "to override!"
+  
+method collide[T](a: TThing, b: TUnit[T]) {.inline.} =
+  write stdout, "collide: thing, unit | "
+
+method collide[T](a: TUnit[T], b: TThing) {.inline.} =
+  write stdout, "collide: unit, thing | "
+
+proc test(a, b: TThing) {.inline.} =
+  collide(a, b)
+
+var
+  a: TThing
+  b, c: TUnit[string]
+collide(b, TThing(c))
+test(b, c)
+collide(a, b)