From dac7644e0df6b848c769752bbb6b76bf65806713 Mon Sep 17 00:00:00 2001
From: Yoshitomo Nakanishi <yurayura.rounin.3@gmail.com>
Date: Mon, 9 Sep 2024 13:34:40 +0200
Subject: [PATCH] Define `Inst` derive proc macro

---
 Cargo.toml               |   1 +
 crates/macros/Cargo.toml |  19 ++++++
 crates/macros/src/lib.rs | 129 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 149 insertions(+)
 create mode 100644 crates/macros/Cargo.toml
 create mode 100644 crates/macros/src/lib.rs

diff --git a/Cargo.toml b/Cargo.toml
index cf02c73c..99947b3a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,5 +7,6 @@ members = [
     "crates/parser",
     "crates/filecheck",
     "crates/triple",
+    "crates/macros",
     "crates/interpreter",
 ]
diff --git a/crates/macros/Cargo.toml b/crates/macros/Cargo.toml
new file mode 100644
index 00000000..408690ef
--- /dev/null
+++ b/crates/macros/Cargo.toml
@@ -0,0 +1,19 @@
+[package]
+name = "sonatina-macros"
+version = "0.0.3-alpha"
+edition = "2021"
+authors = ["Sonatina Developers"]
+license = "Apache-2.0"
+readme = "../../README.md"
+homepage = "https://github.com/fe-lang/sonatina/tree/main/crates/ir"
+repository = "https://github.com/fe-lang/sonatina"
+categories = ["compilers", "wasm"]
+keywords = ["compiler", "evm", "wasm", "smart-contract"]
+
+[lib]
+proc_macro = true
+
+[dependencies]
+syn = { version = "1.0", features = ["full"] }
+proc-macro2 = "1.0"
+quote = "1.0"
diff --git a/crates/macros/src/lib.rs b/crates/macros/src/lib.rs
new file mode 100644
index 00000000..6aa09577
--- /dev/null
+++ b/crates/macros/src/lib.rs
@@ -0,0 +1,129 @@
+use quote::quote;
+
+#[proc_macro_derive(Inst)]
+pub fn derive_inst(item: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let item_struct = syn::parse_macro_input!(item as syn::ItemStruct);
+
+    match InstBuilder::new(item_struct).and_then(InstBuilder::build) {
+        Ok(impls) => quote! {
+            #impls
+        }
+        .into(),
+
+        Err(e) => e.to_compile_error().into(),
+    }
+}
+
+struct InstBuilder {
+    struct_name: syn::Ident,
+    fields: syn::FieldsNamed,
+}
+
+impl InstBuilder {
+    fn new(item_struct: syn::ItemStruct) -> syn::Result<Self> {
+        let struct_ident = item_struct.ident;
+        let syn::Fields::Named(fields) = item_struct.fields else {
+            return Err(syn::Error::new_spanned(
+                item_struct.fields,
+                "tuple struct is not allowed for inst types",
+            ));
+        };
+
+        if item_struct.generics.lt_token.is_some() {
+            Err(syn::Error::new_spanned(
+                item_struct.generics,
+                "generics is not allowed for inst types",
+            ))
+        } else {
+            Ok(Self {
+                struct_name: struct_ident,
+                fields,
+            })
+        }
+    }
+
+    fn build(self) -> syn::Result<proc_macro2::TokenStream> {
+        let mut fields = Vec::with_capacity(self.fields.named.len());
+
+        for f in &self.fields.named {
+            if !matches!(f.vis, syn::Visibility::Inherited) {
+                return Err(syn::Error::new_spanned(
+                    &f.vis,
+                    "all members of inst types should be private",
+                ));
+            };
+
+            fields.push((f.ident.clone().unwrap(), f.ty.clone()));
+        }
+
+        let ctor = self.make_ctor(&fields);
+        let accessors = self.make_accessors(&fields);
+        let cast_fn = self.make_cast_fn();
+
+        let struct_name = &self.struct_name;
+        Ok(quote! {
+            impl #struct_name {
+                #ctor
+
+                #accessors
+
+                #cast_fn
+            }
+        })
+    }
+
+    fn make_ctor(&self, fields: &[(syn::Ident, syn::Type)]) -> proc_macro2::TokenStream {
+        let ctor_args = fields.iter().map(|(ident, ty)| quote! {#ident: #ty});
+        let field_names = fields.iter().map(|(ident, _)| ident);
+        quote! {
+            pub fn new(hi: &dyn crate::HasInst<Self>, #(#ctor_args),*) -> Self {
+                Self {
+                    #(#field_names: #field_names),*
+                }
+            }
+        }
+    }
+
+    fn make_cast_fn(&self) -> proc_macro2::TokenStream {
+        quote! {
+            pub fn cast<'i>(hi: &dyn crate::HasInst<Self>, inst: &'i dyn Inst) -> Option<&'i Self> {
+                if hi.is(inst) {
+                    unsafe { Some(&*(inst as *const dyn Inst as *const Self)) }
+                } else {
+                    None
+                }
+            }
+
+            pub fn cast_mut<'i>(
+                hi: &dyn HasInst<Self>,
+                inst: &'i mut dyn Inst,
+            ) -> Option<&'i mut Self> {
+                if hi.is(inst) {
+                    unsafe { Some(&mut *(inst as *mut dyn Inst as *mut Self)) }
+                } else {
+                    None
+                }
+            }
+        }
+    }
+
+    fn make_accessors(&self, fields: &[(syn::Ident, syn::Type)]) -> proc_macro2::TokenStream {
+        let accessors = fields.iter().map(|(ident, ty)| {
+            let getter = quote::format_ident!("{ident}");
+            let get_mut = quote::format_ident!("{ident}_mut");
+            quote! {
+                pub fn #getter(&self) -> &#ty {
+                    &self.#ident
+                }
+
+                pub fn #get_mut(&mut self) -> &mut #ty{
+                    &mut self.#ident
+                }
+            }
+        });
+
+        quote! {
+            #(#accessors)*
+        }
+    }
+}