From 01c31cb33dd3eb5c4bc7ada1130491434b291c71 Mon Sep 17 00:00:00 2001
From: Ryan Levick <ryan.levick@gmail.com>
Date: Thu, 22 Feb 2018 00:55:11 +0100
Subject: [PATCH] Create Rust wrapping code for enums

---
 crates/wasm-bindgen-macro/src/ast.rs  | 35 ++++++++++++++++++++++++++-
 crates/wasm-bindgen-macro/src/lib.rs  | 30 +++++++++++++++++++++++
 crates/wasm-bindgen-shared/src/lib.rs |  1 +
 3 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/crates/wasm-bindgen-macro/src/ast.rs b/crates/wasm-bindgen-macro/src/ast.rs
index 0920cdac..1899a6dc 100644
--- a/crates/wasm-bindgen-macro/src/ast.rs
+++ b/crates/wasm-bindgen-macro/src/ast.rs
@@ -9,6 +9,7 @@ use syn;
 pub struct Program {
     pub exports: Vec<Export>,
     pub imports: Vec<Import>,
+    pub enums: Vec<Enum>,
     pub imported_types: Vec<(syn::Visibility, syn::Ident)>,
     pub structs: Vec<Struct>,
 }
@@ -47,6 +48,10 @@ pub struct Struct {
     pub name: syn::Ident,
 }
 
+pub struct Enum {
+    pub name: syn::Ident
+}
+
 pub enum Type {
     // special
     Vector(VectorType, bool),
@@ -110,8 +115,13 @@ impl Program {
                 let opts = opts.unwrap_or_else(|| BindgenAttrs::find(&mut f.attrs));
                 self.push_foreign_mod(f, opts);
             }
+            syn::Item::Enum(mut e) => {
+                let opts = opts.unwrap_or_else(|| BindgenAttrs::find(&mut e.attrs));
+                e.to_tokens(tokens);
+                self.push_enum(e, opts);
+            }
             _ => panic!("#[wasm_bindgen] can only be applied to a function, \
-                         struct, impl, or extern block"),
+                         struct, enum, impl, or extern block"),
         }
     }
 
@@ -195,6 +205,28 @@ impl Program {
         }
     }
 
+    pub fn push_enum(&mut self, item: syn::ItemEnum, opts: BindgenAttrs) {
+        match item.vis {
+            syn::Visibility::Public(_) => {}
+            _ => panic!("only public enums are allowed"),
+        }
+
+        let all_fields_unit = item.variants.iter().all(|ref v| {
+            match v.fields {
+                syn::Fields::Unit => true,
+                _ => false
+            }
+        });
+        if all_fields_unit {
+            self.enums.push(Enum {
+                name: item.ident
+            });
+
+        } else {
+            panic!("Only C-Style enums allowed")
+        }
+    }
+
     pub fn push_foreign_fn(&mut self,
                            mut f: syn::ForeignItemFn,
                            module_opts: &BindgenAttrs) {
@@ -301,6 +333,7 @@ impl Program {
                     let names = self.exports.iter()
                         .filter_map(|e| e.class)
                         .chain(self.structs.iter().map(|s| s.name))
+                        .chain(self.enums.iter().map(|s| s.name))
                         .collect::<BTreeSet<_>>();
                     a.list(&names, |s, a| {
                         let val = shared::name_to_descriptor(s.as_ref());
diff --git a/crates/wasm-bindgen-macro/src/lib.rs b/crates/wasm-bindgen-macro/src/lib.rs
index 1878bb00..039d23ff 100644
--- a/crates/wasm-bindgen-macro/src/lib.rs
+++ b/crates/wasm-bindgen-macro/src/lib.rs
@@ -50,6 +50,9 @@ fn generate_wrappers(program: ast::Program, tokens: &mut Tokens) {
     for i in program.imports.iter() {
         bindgen_import(i, tokens);
     }
+    for e in program.enums.iter() {
+        bindgen_enum(e, tokens);
+    }
     for &(ref vis, ref t) in program.imported_types.iter() {
         bindgen_imported_type(vis, t, tokens);
     }
@@ -510,3 +513,30 @@ fn bindgen_import(import: &ast::Import, tokens: &mut Tokens) {
         invocation.to_tokens(tokens);
     }
 }
+
+fn bindgen_enum(e: &ast::Enum, into: &mut Tokens) {
+    let name = &e.name;
+    let c = shared::name_to_descriptor(name.as_ref()) as u32;
+    (my_quote! {
+        impl #name {
+            fn from_usize(n: usize) -> #name {
+                #name::Blue
+            }
+        }
+        impl ::wasm_bindgen::convert::WasmBoundary for #name {
+            type Js = u32;
+            const DESCRIPTOR: u32 = #c;
+
+            fn into_js(self) -> u32 {
+                Box::into_raw(Box::new(self as u32)) as u32
+            }
+
+            unsafe fn from_js(js: u32) -> Self {
+                let js = js as *mut usize;
+                ::wasm_bindgen::__rt::assert_not_null(js);
+                let js = Box::from_raw(js);
+                #name::from_usize(*js)
+            }
+        }
+    }).to_tokens(into);
+}
diff --git a/crates/wasm-bindgen-shared/src/lib.rs b/crates/wasm-bindgen-shared/src/lib.rs
index 7fe56b5d..2047ce99 100644
--- a/crates/wasm-bindgen-shared/src/lib.rs
+++ b/crates/wasm-bindgen-shared/src/lib.rs
@@ -77,6 +77,7 @@ pub fn mangled_import_name(struct_: Option<&str>, f: &str) -> String {
 
 pub type Type = char;
 
+pub const TYPE_ENUM: char = '\u{5d}';
 pub const TYPE_NUMBER: char = '\u{5e}';
 pub const TYPE_BORROWED_STR: char = '\u{5f}';
 pub const TYPE_STRING: char = '\u{60}';