Fixes #17433; gensym callDef return in templ body (#17445)

tests/template/t17433.nim

@@ -0,0 +1,16 @@
+# Inside template bodies, ensure return types referencing a param are replaced.
+# This helps guarantee that return parameter analysis happens after argument
+# analysis.
+ 
+# bug #17433
+
+from std/macros import expandMacros
+
+proc bar(a: typedesc): a = default(a)
+assert bar(float) == 0.0
+assert bar(string) == ""
+
+template main =
+  proc baz(a: typedesc): a = default(a)
+  assert baz(float) == 0.0
+main()