fix #1820

compiler/sigmatch.nim

@@ -989,7 +989,7 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
     if aOrig.kind == tyStatic:
       result = typeRel(c, f.lastSon, a)
       if result != isNone and f.n != nil:
-        if not exprStructuralEquivalent(f.n, a.n):
+        if not exprStructuralEquivalent(f.n, aOrig.n):
           result = isNone
       if result != isNone: put(c.bindings, f, aOrig)
     else:

tests/metatype/tstaticparams.nim

@@ -1,6 +1,6 @@
 discard """
   file: "tstaticparams.nim"
-  output: "abracadabra\ntest\n3\n15\n4\n2"
+  output: "abracadabra\ntest\n3\n15\n4\n2\nfloat\n3\nfloat\nyin\nyang"
 """
 
 type 
@@ -83,3 +83,39 @@ reject matrix_2(tmat, ar1)
 reject matrix_3(tmat, ar2)
 reject matrix_4(tmat, ar1)
 
+# bug 1820
+
+type
+  T1820_1[T; Y: static[int]] = object
+    bar: T
+
+proc intOrFloat*[Y](f: T1820_1[int, Y]) = echo "int"
+proc intOrFloat*[Y](f: T1820_1[float, Y]) = echo "float"
+proc threeOrFour*[T](f: T1820_1[T, 3]) =  echo "3"
+proc threeOrFour*[T](f: T1820_1[T, 4]) = echo "4"
+
+var foo_1: T1820_1[float, 3]
+
+foo_1.intOrFloat
+foo_1.threeOrFour
+
+type
+  YinAndYang = enum
+    Yin,
+    Yang
+
+  T1820_2[T; Y: static[YinAndYang]] = object
+    bar: T
+
+proc intOrFloat*[Y](f: T1820_2[int, Y]) = echo "int"
+proc intOrFloat*[Y](f: T1820_2[float, Y]) = echo "float"
+proc yinOrYang*[T](f: T1820_2[T, YinAndYang.Yin]) = echo "yin"
+proc yinOrYang*[T](f: T1820_2[T, Yang]) = echo "yang"
+
+var foo_2: T1820_2[float, Yin]
+var foo_3: T1820_2[float, YinAndYang.Yang]
+
+foo_2.intOrFloat
+foo_2.yinOrYang
+foo_3.yinOrYang
+