Adds demo of using a macro to generate specialized macros (#141)

conformance/README.md

@@ -10,6 +10,7 @@ declarative domain-specific language.
  * `ion_encoding/` – test cases for encoding directives
    * `module/`
  * `system_macros/` – test cases for each of the system macros
+ * `demos/` – contains demonstrations of interesting and/or useful strategies
 
 > [!WARNING]
 > This test suite and its DSL are **Work In Progress**.

conformance/demos/metaprogramming.ion

@@ -0,0 +1,35 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+(ion_1_1 "a macro that can create a monomorphized variant of the values macro"
+         (mactab (macro tiny_decimal (int8::a int8::b) (.make_decimal a b))
+                 (macro tagless_values (mod_or_type type?)
+                        (macro
+                          // Macro name
+                          (.$ion::make_symbol (.. (%mod_or_type) (.$ion::if_some (%type) "_") (%type) "_values"))
+                          // Signature
+                          ((.$ion::annotate (.. (%mod_or_type) (%type)) vals) *)
+                          // Body
+                          ((.$ion::values %) vals))
+                 ))
+         (then "for a built-in encoding type"
+               (toplevel ('#$:$ion::add_macros' ('#$:tagless_values' uint8)))
+               (then "when invoked in Ion text"
+                     (text "(:uint8_values 1 2 3 4 5)")
+                     (produces 1 2 3 4 5))
+               (then "when invoked in Ion binary"
+                     // Invoke our new "uint8_values" macro
+                     (binary "02 02 0B 01 02 03 04 05")
+                     (produces 1 2 3 4 5)))
+         (then "for a macro-shape"
+               (toplevel ('#$:$ion::add_macros' ('#$:tagless_values' tiny_decimal)))
+               // TODO: Add case demoing binary
+               (then "when invoked in Ion text"
+                     (text "(:tiny_decimal_values (1 2) (3 4))")
+                     (produces 1d2 3d4)))
+         (then "for a qualified type name"
+               (toplevel ('#$:$ion::add_macros' ('#$:tagless_values' $ion make_decimal)))
+               // TODO: Add case demoing binary
+               (then "when invoked in Ion text"
+                     (text "(:$ion_make_decimal_values (1 2) (3 4))")
+                     (produces 1d2 3d4))))