1 files changed, 141 insertions, 0 deletions

diff --git a/crates/syntax/src/ast/traits.rs b/crates/syntax/src/ast/traits.rs
new file mode 100644
index 000000000..0bdc22d95
--- /dev/null
+++ b/crates/syntax/src/ast/traits.rs
@@ -0,0 +1,141 @@
+//! Various traits that are implemented by ast nodes.
+//!
+//! The implementations are usually trivial, and live in generated.rs
+use itertools::Itertools;
+
+use crate::{
+    ast::{self, support, AstChildren, AstNode, AstToken},
+    syntax_node::SyntaxElementChildren,
+    SyntaxToken, T,
+};
+
+pub trait NameOwner: AstNode {
+    fn name(&self) -> Option<ast::Name> {
+        support::child(self.syntax())
+    }
+}
+
+pub trait VisibilityOwner: AstNode {
+    fn visibility(&self) -> Option<ast::Visibility> {
+        support::child(self.syntax())
+    }
+}
+
+pub trait LoopBodyOwner: AstNode {
+    fn loop_body(&self) -> Option<ast::BlockExpr> {
+        support::child(self.syntax())
+    }
+
+    fn label(&self) -> Option<ast::Label> {
+        support::child(self.syntax())
+    }
+}
+
+pub trait ArgListOwner: AstNode {
+    fn arg_list(&self) -> Option<ast::ArgList> {
+        support::child(self.syntax())
+    }
+}
+
+pub trait ModuleItemOwner: AstNode {
+    fn items(&self) -> AstChildren<ast::Item> {
+        support::children(self.syntax())
+    }
+}
+
+pub trait GenericParamsOwner: AstNode {
+    fn generic_param_list(&self) -> Option<ast::GenericParamList> {
+        support::child(self.syntax())
+    }
+
+    fn where_clause(&self) -> Option<ast::WhereClause> {
+        support::child(self.syntax())
+    }
+}
+
+pub trait TypeBoundsOwner: AstNode {
+    fn type_bound_list(&self) -> Option<ast::TypeBoundList> {
+        support::child(self.syntax())
+    }
+
+    fn colon_token(&self) -> Option<SyntaxToken> {
+        support::token(self.syntax(), T![:])
+    }
+}
+
+pub trait AttrsOwner: AstNode {
+    fn attrs(&self) -> AstChildren<ast::Attr> {
+        support::children(self.syntax())
+    }
+    fn has_atom_attr(&self, atom: &str) -> bool {
+        self.attrs().filter_map(|x| x.as_simple_atom()).any(|x| x == atom)
+    }
+}
+
+pub trait DocCommentsOwner: AstNode {
+    fn doc_comments(&self) -> CommentIter {
+        CommentIter { iter: self.syntax().children_with_tokens() }
+    }
+
+    fn doc_comment_text(&self) -> Option<String> {
+        self.doc_comments().doc_comment_text()
+    }
+}
+
+impl CommentIter {
+    pub fn from_syntax_node(syntax_node: &ast::SyntaxNode) -> CommentIter {
+        CommentIter { iter: syntax_node.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),
+    /// trailing `*/`, trailing whitespace and then joins the lines.
+    pub fn doc_comment_text(self) -> Option<String> {
+        let mut has_comments = false;
+        let docs = self
+            .filter(|comment| comment.kind().doc.is_some())
+            .map(|comment| {
+                has_comments = true;
+                let prefix_len = comment.prefix().len();
+
+                let line: &str = comment.text().as_str();
+
+                // Determine if the prefix or prefix + 1 char is stripped
+                let pos =
+                    if let Some(ws) = line.chars().nth(prefix_len).filter(|c| c.is_whitespace()) {
+                        prefix_len + ws.len_utf8()
+                    } else {
+                        prefix_len
+                    };
+
+                let end = if comment.kind().shape.is_block() && line.ends_with("*/") {
+                    line.len() - 2
+                } else {
+                    line.len()
+                };
+
+                // Note that we do not trim the end of the line here
+                // since whitespace can have special meaning at the end
+                // of a line in markdown.
+                line[pos..end].to_owned()
+            })
+            .join("\n");
+
+        if has_comments {
+            Some(docs)
+        } else {
+            None
+        }
+    }
+}
+
+pub struct CommentIter {
+    iter: SyntaxElementChildren,
+}
+
+impl Iterator for CommentIter {
+    type Item = ast::Comment;
+    fn next(&mut self) -> Option<ast::Comment> {
+        self.iter.by_ref().find_map(|el| el.into_token().and_then(ast::Comment::cast))
+    }
+}