1 files changed, 71 insertions, 0 deletions

diff --git a/crates/hir_def/src/nameres/proc_macro.rs b/crates/hir_def/src/nameres/proc_macro.rs
new file mode 100644
index 000000000..156598f19
--- /dev/null
+++ b/crates/hir_def/src/nameres/proc_macro.rs
@@ -0,0 +1,71 @@
+//! Nameres-specific procedural macro data and helpers.
+
+use hir_expand::name::{AsName, Name};
+use tt::{Leaf, TokenTree};
+
+use crate::attr::Attrs;
+
+#[derive(Debug, PartialEq, Eq)]
+pub(super) struct ProcMacroDef {
+    pub(super) name: Name,
+    pub(super) kind: ProcMacroKind,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub(super) enum ProcMacroKind {
+    CustomDerive { helpers: Box<[Name]> },
+    FnLike,
+    Attr,
+}
+
+impl Attrs {
+    #[rustfmt::skip]
+    pub(super) fn parse_proc_macro_decl(&self, func_name: &Name) -> Option<ProcMacroDef> {
+        if self.by_key("proc_macro").exists() {
+            Some(ProcMacroDef { name: func_name.clone(), kind: ProcMacroKind::FnLike })
+        } else if self.by_key("proc_macro_attribute").exists() {
+            Some(ProcMacroDef { name: func_name.clone(), kind: ProcMacroKind::Attr })
+        } else if self.by_key("proc_macro_derive").exists() {
+            let derive = self.by_key("proc_macro_derive").tt_values().next().unwrap();
+
+            match &*derive.token_trees {
+                // `#[proc_macro_derive(Trait)]`
+                [TokenTree::Leaf(Leaf::Ident(trait_name))] => Some(ProcMacroDef {
+                    name: trait_name.as_name(),
+                    kind: ProcMacroKind::CustomDerive { helpers: Box::new([]) },
+                }),
+
+                // `#[proc_macro_derive(Trait, attibutes(helper1, helper2, ...))]`
+                [
+                    TokenTree::Leaf(Leaf::Ident(trait_name)),
+                    TokenTree::Leaf(Leaf::Punct(comma)),
+                    TokenTree::Leaf(Leaf::Ident(attributes)),
+                    TokenTree::Subtree(helpers)
+                ] if comma.char == ',' && attributes.text == "attributes" =>
+                {
+                    let helpers = helpers.token_trees.iter()
+                        .filter(|tt| !matches!(tt, TokenTree::Leaf(Leaf::Punct(comma)) if comma.char == ','))
+                        .map(|tt| {
+                            match tt {
+                                TokenTree::Leaf(Leaf::Ident(helper)) => Some(helper.as_name()),
+                                _ => None
+                            }
+                        })
+                        .collect::<Option<Box<[_]>>>()?;
+
+                    Some(ProcMacroDef {
+                        name: trait_name.as_name(),
+                        kind: ProcMacroKind::CustomDerive { helpers },
+                    })
+                }
+
+                _ => {
+                    log::trace!("malformed `#[proc_macro_derive]`: {}", derive);
+                    None
+                }
+            }
+        } else {
+            None
+        }
+    }
+}