2 files changed, 94 insertions, 1 deletions

diff --git a/crates/ra_syntax/src/ast/tokens.rs b/crates/ra_syntax/src/ast/tokens.rs
new file mode 100644
index 000000000..c830cdccf
--- /dev/null
+++ b/crates/ra_syntax/src/ast/tokens.rs
@@ -0,0 +1,93 @@
+use crate::{
+    SyntaxToken,
+    SyntaxKind::{COMMENT, WHITESPACE},
+    ast::AstToken,
+};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Comment<'a>(SyntaxToken<'a>);
+
+impl<'a> AstToken<'a> for Comment<'a> {
+    fn cast(token: SyntaxToken<'a>) -> Option<Self> {
+        if token.kind() == COMMENT {
+            Some(Comment(token))
+        } else {
+            None
+        }
+    }
+    fn syntax(&self) -> SyntaxToken<'a> {
+        self.0
+    }
+}
+
+impl<'a> Comment<'a> {
+    pub fn flavor(&self) -> CommentFlavor {
+        let text = self.text();
+        if text.starts_with("///") {
+            CommentFlavor::Doc
+        } else if text.starts_with("//!") {
+            CommentFlavor::ModuleDoc
+        } else if text.starts_with("//") {
+            CommentFlavor::Line
+        } else {
+            CommentFlavor::Multiline
+        }
+    }
+
+    pub fn is_doc_comment(&self) -> bool {
+        self.flavor().is_doc_comment()
+    }
+
+    pub fn prefix(&self) -> &'static str {
+        self.flavor().prefix()
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum CommentFlavor {
+    Line,
+    Doc,
+    ModuleDoc,
+    Multiline,
+}
+
+impl CommentFlavor {
+    pub fn prefix(&self) -> &'static str {
+        use self::CommentFlavor::*;
+        match *self {
+            Line => "//",
+            Doc => "///",
+            ModuleDoc => "//!",
+            Multiline => "/*",
+        }
+    }
+
+    pub fn is_doc_comment(&self) -> bool {
+        match self {
+            CommentFlavor::Doc | CommentFlavor::ModuleDoc => true,
+            _ => false,
+        }
+    }
+}
+
+pub struct Whitespace<'a>(SyntaxToken<'a>);
+
+impl<'a> AstToken<'a> for Whitespace<'a> {
+    fn cast(token: SyntaxToken<'a>) -> Option<Self> {
+        if token.kind() == WHITESPACE {
+            Some(Whitespace(token))
+        } else {
+            None
+        }
+    }
+    fn syntax(&self) -> SyntaxToken<'a> {
+        self.0
+    }
+}
+
+impl<'a> Whitespace<'a> {
+    pub fn spans_multiple_lines(&self) -> bool {
+        let text = self.text();
+        text.find('\n').map_or(false, |idx| text[idx + 1..].contains('\n'))
+    }
+}
diff --git a/crates/ra_syntax/src/ast/traits.rs b/crates/ra_syntax/src/ast/traits.rs
index 85fe6d5e1..f9021d7bf 100644
--- a/crates/ra_syntax/src/ast/traits.rs
+++ b/crates/ra_syntax/src/ast/traits.rs
@@ -2,7 +2,7 @@ use itertools::Itertools;
 
 use crate::{
     syntax_node::{SyntaxNodeChildren, SyntaxElementChildren},
-    ast::{self, child_opt, children, AstNode, AstChildren},
+    ast::{self, child_opt, children, AstNode, AstToken, AstChildren},
 };
 
 pub trait TypeAscriptionOwner: AstNode {