From 97e5e62b03c45c0f8a587fb1ca06b64d95df78e9 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Mon, 6 May 2024 19:17:31 +0100
Subject: [PATCH] REPRO

---
 Cargo.lock        |  1 +
 macros/Cargo.toml |  1 +
 macros/macros.rs  | 32 ++++++++++++++++++++++++--------
 src/main.rs       | 23 ++++++++++++++++++-----
 4 files changed, 44 insertions(+), 13 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index fceca33..d5c0119 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -14,6 +14,7 @@ name = "foo-macros"
 version = "0.1.0"
 dependencies = [
  "proc-macro2",
+ "quote",
  "syn",
 ]
 
diff --git a/macros/Cargo.toml b/macros/Cargo.toml
index 78cd50d..5e65c89 100644
--- a/macros/Cargo.toml
+++ b/macros/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2021"
 [dependencies]
 syn = "2"
 proc-macro2 = "1"
+quote = "1"
 
 [lib]
 path = "macros.rs"
diff --git a/macros/macros.rs b/macros/macros.rs
index ad774d0..1c4f685 100644
--- a/macros/macros.rs
+++ b/macros/macros.rs
@@ -1,11 +1,27 @@
-use proc_macro2::TokenStream as TokenStream2;
+use proc_macro::TokenStream;
+use quote::{quote, ToTokens};
+use proc_macro2::Delimiter;
 
 #[proc_macro]
-pub fn reparse(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
-    let input: TokenStream2 = input.into();
-    let input: syn::LitStr = syn::parse2(input).expect("not litstr?");
-    let reparsed: TokenStream2 = input.parse().unwrap_or_else(|e| {
-        e.into_compile_error()
-    });
-    reparsed.into()
+pub fn dbg_dump(input: TokenStream) -> TokenStream {
+    dbg!(&input);
+    input
+}
+
+#[proc_macro]
+pub fn define_struct_procmacro(input: TokenStream) -> TokenStream {
+    let ty: syn::Type = syn::parse(input).unwrap();
+    let ty = proc_macro2::Group::new(
+        Delimiter::None,
+        ty.to_token_stream(),
+    );
+    let out: TokenStream = quote! {
+        struct FromProcMacro {
+            field: &'static #ty,
+        }
+    }.into();
+
+    dbg!(&out);
+
+    out
 }
diff --git a/src/main.rs b/src/main.rs
index 89ed347..d496be6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,19 @@
-use foo_macros::reparse;
+#![allow(dead_code)]
 
-fn main() {
-    let s = reparse!(" { ");
-    println!("{s:?}");
-}
+use foo_macros::*;
+
+use std::fmt::Display;
+
+macro_rules! define_struct_pattern { { $ftype:ty } => {
+    foo_macros::dbg_dump! {
+        struct FromPatternMacro {
+            field: &'static $ftype,
+        }
+    }
+} }
+
+define_struct_pattern!{ dyn Display + 'static }
+
+define_struct_procmacro!{ dyn Display + 'static }
+
+fn main() {}
-- 
2.30.2