Try conversion to static[T] in generic instantation (#8443)

Fixes #8439

compiler/semcall.nim

@@ -505,7 +505,15 @@ proc explicitGenericSym(c: PContext, n: PNode, s: PSym): PNode =
 
   for i in 1..sonsLen(n)-1:
     let formal = s.ast.sons[genericParamsPos].sons[i-1].typ
-    let arg = n[i].typ
+    var arg = n[i].typ
+    # try transforming the argument into a static one before feeding it into
+    # typeRel
+    if formal.kind == tyStatic and arg.kind != tyStatic:
+      let evaluated = c.semTryConstExpr(c, n[i])
+      if evaluated != nil:
+        arg = newTypeS(tyStatic, c)
+        arg.sons = @[evaluated.typ]
+        arg.n = evaluated
     let tm = typeRel(m, formal, arg)
     if tm in {isNone, isConvertible}: return nil
   var newInst = generateInstance(c, s, m.bindings, n.info)

tests/generics/t8439.nim

@@ -0,0 +1,10 @@
+discard """
+  output: "1"
+"""
+
+type
+  Cardinal = enum
+    north, east, south, west
+
+proc foo[cardinal: static[Cardinal]](): int = 1
+echo(foo[north]())