1 files changed, 150 insertions, 0 deletions

diff --git a/crates/ra_syntax/src/ast/traits.rs b/crates/ra_syntax/src/ast/traits.rs
new file mode 100644
index 000000000..43d1509fa
--- /dev/null
+++ b/crates/ra_syntax/src/ast/traits.rs
@@ -0,0 +1,150 @@
+use itertools::Itertools;
+
+use crate::{
+    syntax_node::{SyntaxNodeChildren, SyntaxElementChildren},
+    ast::{self, child_opt, children, AstNode, AstToken, AstChildren},
+};
+
+pub trait TypeAscriptionOwner: AstNode {
+    fn ascribed_type(&self) -> Option<&ast::TypeRef> {
+        child_opt(self)
+    }
+}
+
+pub trait NameOwner: AstNode {
+    fn name(&self) -> Option<&ast::Name> {
+        child_opt(self)
+    }
+}
+
+pub trait VisibilityOwner: AstNode {
+    fn visibility(&self) -> Option<&ast::Visibility> {
+        child_opt(self)
+    }
+}
+
+pub trait LoopBodyOwner: AstNode {
+    fn loop_body(&self) -> Option<&ast::Block> {
+        child_opt(self)
+    }
+}
+
+pub trait ArgListOwner: AstNode {
+    fn arg_list(&self) -> Option<&ast::ArgList> {
+        child_opt(self)
+    }
+}
+
+pub trait FnDefOwner: AstNode {
+    fn functions(&self) -> AstChildren<ast::FnDef> {
+        children(self)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ItemOrMacro<'a> {
+    Item(&'a ast::ModuleItem),
+    Macro(&'a ast::MacroCall),
+}
+
+pub trait ModuleItemOwner: AstNode {
+    fn items(&self) -> AstChildren<ast::ModuleItem> {
+        children(self)
+    }
+    fn items_with_macros(&self) -> ItemOrMacroIter {
+        ItemOrMacroIter(self.syntax().children())
+    }
+}
+
+#[derive(Debug)]
+pub struct ItemOrMacroIter<'a>(SyntaxNodeChildren<'a>);
+
+impl<'a> Iterator for ItemOrMacroIter<'a> {
+    type Item = ItemOrMacro<'a>;
+    fn next(&mut self) -> Option<ItemOrMacro<'a>> {
+        loop {
+            let n = self.0.next()?;
+            if let Some(item) = ast::ModuleItem::cast(n) {
+                return Some(ItemOrMacro::Item(item));
+            }
+            if let Some(call) = ast::MacroCall::cast(n) {
+                return Some(ItemOrMacro::Macro(call));
+            }
+        }
+    }
+}
+
+pub trait TypeParamsOwner: AstNode {
+    fn type_param_list(&self) -> Option<&ast::TypeParamList> {
+        child_opt(self)
+    }
+
+    fn where_clause(&self) -> Option<&ast::WhereClause> {
+        child_opt(self)
+    }
+}
+
+pub trait TypeBoundsOwner: AstNode {
+    fn type_bound_list(&self) -> Option<&ast::TypeBoundList> {
+        child_opt(self)
+    }
+}
+
+pub trait AttrsOwner: AstNode {
+    fn attrs(&self) -> AstChildren<ast::Attr> {
+        children(self)
+    }
+    fn has_atom_attr(&self, atom: &str) -> bool {
+        self.attrs().filter_map(|x| x.as_atom()).any(|x| x == atom)
+    }
+}
+
+pub trait DocCommentsOwner: AstNode {
+    fn doc_comments(&self) -> CommentIter {
+        CommentIter { iter: self.syntax().children_with_tokens() }
+    }
+
+    /// Returns the textual content of a doc comment block as a single string.
+    /// That is, strips leading `///` (+ optional 1 character of whitespace)
+    /// and joins lines.
+    fn doc_comment_text(&self) -> Option<String> {
+        let mut has_comments = false;
+        let docs = self
+            .doc_comments()
+            .filter(|comment| comment.is_doc_comment())
+            .map(|comment| {
+                has_comments = true;
+                let prefix_len = comment.prefix().len();
+
+                let line = comment.text().as_str();
+
+                // Determine if the prefix or prefix + 1 char is stripped
+                let pos =
+                    if line.chars().nth(prefix_len).map(|c| c.is_whitespace()).unwrap_or(false) {
+                        prefix_len + 1
+                    } else {
+                        prefix_len
+                    };
+
+                line[pos..].to_owned()
+            })
+            .join("\n");
+
+        if has_comments {
+            Some(docs)
+        } else {
+            None
+        }
+    }
+}
+
+pub struct CommentIter<'a> {
+    iter: SyntaxElementChildren<'a>,
+}
+
+impl<'a> Iterator for CommentIter<'a> {
+    type Item = ast::Comment<'a>;
+    fn next(&mut self) -> Option<ast::Comment<'a>> {
+        self.iter.by_ref().find_map(|el| el.as_token().and_then(ast::Comment::cast))
+    }
+}