whitelist generic params matching typedesc for templates/macros

fixes #23432

compiler/sigmatch.nim

@@ -1905,10 +1905,12 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
       # when `f` is an unresolved typedesc, `a` could be any
       # type, so we should not perform this check earlier
       if c.c.inGenericContext > 0 and
-          a.skipTypes({tyTypeDesc}).kind == tyGenericParam:
+          a.skipTypes({tyTypeDesc}).kind == tyGenericParam and
+          not (c.calleeSym != nil and c.calleeSym.kind in {skMacro, skTemplate}):
         # generic type bodies can sometimes compile call expressions
         # prevent unresolved generic parameters from being passed to procs as
         # typedesc parameters
+        # macros and templates receive a pass for practicality
         result = isNone
       elif a.kind != tyTypeDesc:
         if a.kind == tyGenericParam and tfWildcard in a.flags:

tests/generics/tmacrotype.nim

@@ -0,0 +1,28 @@
+import std/[sequtils, macros]
+
+block: # issue #23432
+  type
+    Future[T] = object
+    InternalRaisesFuture[T, E] = object
+
+  macro Raising[T](F: typedesc[Future[T]], E: varargs[typedesc]): untyped =
+    ## Given a Future type instance, return a type storing `{.raises.}`
+    ## information
+    ##
+    ## Note; this type may change in the future
+    E.expectKind(nnkBracket)
+
+    let raises = nnkTupleConstr.newTree(E.mapIt(it))
+    nnkBracketExpr.newTree(
+      ident "InternalRaisesFuture",
+      nnkDotExpr.newTree(F, ident"T"),
+      raises
+    )
+
+  type X[E] = Future[void].Raising(E)
+
+  proc f(x: X) = discard
+
+
+  var v: Future[void].Raising([ValueError])
+  f(v)