fixes #2304

compiler/ast.nim

@@ -919,6 +919,8 @@ const
     # only used when 'gCmd == cmdPretty': Indicates that the symbol has been
     # imported via 'importc: "fullname"' and no format string.
 
+var ggDebug* {.deprecated.}: bool ## convenience switch for trying out things
+
 proc isCallExpr*(n: PNode): bool =
   result = n.kind in nkCallKinds
 

compiler/semtypes.nim

@@ -352,7 +352,7 @@ proc semAnonTuple(c: PContext, n: PNode, prev: PType): PType =
   for i in countup(0, sonsLen(n) - 1):
     addSonSkipIntLit(result, semTypeNode(c, n.sons[i], nil))
 
-proc semTuple(c: PContext, n: PNode, prev: PType): PType = 
+proc semTuple(c: PContext, n: PNode, prev: PType): PType =
   var typ: PType
   result = newOrPrevType(tyTuple, prev, c)
   result.n = newNodeI(nkRecList, n.info)
@@ -1045,8 +1045,8 @@ proc semGeneric(c: PContext, n: PNode, s: PSym, prev: PType): PType =
     var m = newCandidate(c, t)
     matches(c, n, copyTree(n), m)
 
-    if m.state != csMatch:
-      var err = "cannot instantiate " & typeToString(t) & "\n" &
+    if m.state != csMatch and not m.typedescMatched:
+      let err = "cannot instantiate " & typeToString(t) & "\n" &
                 "got: (" & describeArgs(c, n) & ")\n" &
                 "but expected: (" & describeArgs(c, t.n, 0) & ")"
       localError(n.info, errGenerated, err)

compiler/sigmatch.nim

@@ -46,7 +46,7 @@ type
                              # be instantiated
     coerceDistincts*: bool   # this is an explicit coercion that can strip away
                              # a distrinct type
-    typedescMatched: bool
+    typedescMatched*: bool
     inheritancePenalty: int  # to prefer closest father object type
     errors*: CandidateErrors # additional clarifications to be displayed to the
                              # user if overload resolution fails
@@ -989,7 +989,11 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
           else:
             internalAssert a.sons != nil and a.sons.len > 0
             c.typedescMatched = true
-            result = typeRel(c, f.base, a.skipTypes({tyGenericParam, tyTypeDesc}))
+            var aa = a
+            while aa.kind in {tyTypeDesc, tyGenericParam} and
+                aa.len > 0:
+              aa = lastSon(aa)
+            result = typeRel(c, f.base, aa)
             if result > isGeneric: result = isGeneric
         else:
           result = isNone

tests/generics/tarray_with_somenumber.nim

@@ -0,0 +1,11 @@
+discard """
+  output: '''@[0.9, 0.1]'''
+"""
+
+# bug #2304
+
+type TV2*[T:SomeNumber] = array[0..1, T]
+proc newV2T*[T](x, y: T=0): TV2[T] = [x, y]
+
+let x = newV2T[float](0.9, 0.1)
+echo(@x)