1 files changed, 84 insertions, 0 deletions

diff --git a/crates/ra_hir_def/src/attr.rs b/crates/ra_hir_def/src/attr.rs
new file mode 100644
index 000000000..0e961ca12
--- /dev/null
+++ b/crates/ra_hir_def/src/attr.rs
@@ -0,0 +1,84 @@
+//! A higher level attributes based on TokenTree, with also some shortcuts.
+
+use std::sync::Arc;
+
+use hir_expand::hygiene::Hygiene;
+use mbe::ast_to_token_tree;
+use ra_cfg::CfgOptions;
+use ra_syntax::{
+    ast::{self, AstNode, AttrsOwner},
+    SmolStr,
+};
+use tt::Subtree;
+
+use crate::path::Path;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Attr {
+    pub(crate) path: Path,
+    pub(crate) input: Option<AttrInput>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum AttrInput {
+    Literal(SmolStr),
+    TokenTree(Subtree),
+}
+
+impl Attr {
+    pub(crate) fn from_src(ast: ast::Attr, hygiene: &Hygiene) -> Option<Attr> {
+        let path = Path::from_src(ast.path()?, hygiene)?;
+        let input = match ast.input() {
+            None => None,
+            Some(ast::AttrInput::Literal(lit)) => {
+                // FIXME: escape? raw string?
+                let value = lit.syntax().first_token()?.text().trim_matches('"').into();
+                Some(AttrInput::Literal(value))
+            }
+            Some(ast::AttrInput::TokenTree(tt)) => {
+                Some(AttrInput::TokenTree(ast_to_token_tree(&tt)?.0))
+            }
+        };
+
+        Some(Attr { path, input })
+    }
+
+    pub fn from_attrs_owner(owner: &dyn AttrsOwner, hygiene: &Hygiene) -> Option<Arc<[Attr]>> {
+        let mut attrs = owner.attrs().peekable();
+        if attrs.peek().is_none() {
+            // Avoid heap allocation
+            return None;
+        }
+        Some(attrs.flat_map(|ast| Attr::from_src(ast, hygiene)).collect())
+    }
+
+    pub fn is_simple_atom(&self, name: &str) -> bool {
+        // FIXME: Avoid cloning
+        self.path.as_ident().map_or(false, |s| s.to_string() == name)
+    }
+
+    // FIXME: handle cfg_attr :-)
+    pub fn as_cfg(&self) -> Option<&Subtree> {
+        if !self.is_simple_atom("cfg") {
+            return None;
+        }
+        match &self.input {
+            Some(AttrInput::TokenTree(subtree)) => Some(subtree),
+            _ => None,
+        }
+    }
+
+    pub fn as_path(&self) -> Option<&SmolStr> {
+        if !self.is_simple_atom("path") {
+            return None;
+        }
+        match &self.input {
+            Some(AttrInput::Literal(it)) => Some(it),
+            _ => None,
+        }
+    }
+
+    pub fn is_cfg_enabled(&self, cfg_options: &CfgOptions) -> Option<bool> {
+        cfg_options.is_cfg_enabled(self.as_cfg()?)
+    }
+}