5 files changed, 63 insertions, 12 deletions

diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index 7fca5661e..a716e525b 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -243,6 +243,21 @@ fn test_comments_preserve_trailing_whitespace() {
 }
 
 #[test]
+fn test_four_slash_line_comment() {
+    let file = SourceFile::parse(
+        r#"
+        //// too many slashes to be a doc comment
+        /// doc comment
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert_eq!("doc comment", module.doc_comment_text().unwrap());
+}
+
+#[test]
 fn test_where_predicates() {
     fn assert_bound(text: &str, bound: Option<TypeBound>) {
         assert_eq!(text, bound.unwrap().syntax().text().to_string());
diff --git a/crates/ra_syntax/src/ast/generated/nodes.rs b/crates/ra_syntax/src/ast/generated/nodes.rs
index 2cb3ad011..3b5e05af9 100644
--- a/crates/ra_syntax/src/ast/generated/nodes.rs
+++ b/crates/ra_syntax/src/ast/generated/nodes.rs
@@ -1249,6 +1249,7 @@ pub struct PathSegment {
 }
 impl PathSegment {
     pub fn coloncolon_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![::]) }
+    pub fn crate_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![crate]) }
     pub fn l_angle_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![<]) }
     pub fn name_ref(&self) -> Option<NameRef> { support::child(&self.syntax) }
     pub fn type_arg_list(&self) -> Option<TypeArgList> { support::child(&self.syntax) }
diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index ee0f5cc40..492088353 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -22,8 +22,7 @@ pub fn path_unqualified(segment: ast::PathSegment) -> ast::Path {
 pub fn path_qualified(qual: ast::Path, segment: ast::PathSegment) -> ast::Path {
     path_from_text(&format!("{}::{}", qual, segment))
 }
-
-pub fn path_from_text(text: &str) -> ast::Path {
+fn path_from_text(text: &str) -> ast::Path {
     ast_from_text(text)
 }
 
diff --git a/crates/ra_syntax/src/ast/tokens.rs b/crates/ra_syntax/src/ast/tokens.rs
index 3865729b8..74906d8a6 100644
--- a/crates/ra_syntax/src/ast/tokens.rs
+++ b/crates/ra_syntax/src/ast/tokens.rs
@@ -13,7 +13,12 @@ impl Comment {
     }
 
     pub fn prefix(&self) -> &'static str {
-        prefix_by_kind(self.kind())
+        for (prefix, k) in COMMENT_PREFIX_TO_KIND.iter() {
+            if *k == self.kind() && self.text().starts_with(prefix) {
+                return prefix;
+            }
+        }
+        unreachable!()
     }
 }
 
@@ -48,6 +53,7 @@ pub enum CommentPlacement {
 const COMMENT_PREFIX_TO_KIND: &[(&str, CommentKind)] = {
     use {CommentPlacement::*, CommentShape::*};
     &[
+        ("////", CommentKind { shape: Line, doc: None }),
         ("///", CommentKind { shape: Line, doc: Some(Outer) }),
         ("//!", CommentKind { shape: Line, doc: Some(Inner) }),
         ("/**", CommentKind { shape: Block, doc: Some(Outer) }),
@@ -69,15 +75,6 @@ fn kind_by_prefix(text: &str) -> CommentKind {
     panic!("bad comment text: {:?}", text)
 }
 
-fn prefix_by_kind(kind: CommentKind) -> &'static str {
-    for (prefix, k) in COMMENT_PREFIX_TO_KIND.iter() {
-        if *k == kind {
-            return prefix;
-        }
-    }
-    unreachable!()
-}
-
 impl Whitespace {
     pub fn spans_multiple_lines(&self) -> bool {
         let text = self.text();
diff --git a/crates/ra_syntax/src/validation.rs b/crates/ra_syntax/src/validation.rs
index 5e93895ec..a30bc97bb 100644
--- a/crates/ra_syntax/src/validation.rs
+++ b/crates/ra_syntax/src/validation.rs
@@ -96,6 +96,7 @@ pub(crate) fn validate(root: &SyntaxNode) -> Vec<SyntaxError> {
                 ast::RecordField(it) => validate_numeric_name(it.name_ref(), &mut errors),
                 ast::Visibility(it) => validate_visibility(it, &mut errors),
                 ast::RangeExpr(it) => validate_range_expr(it, &mut errors),
+                ast::PathSegment(it) => validate_crate_keyword_in_path_segment(it, &mut errors),
                 _ => (),
             }
         }
@@ -222,3 +223,41 @@ fn validate_range_expr(expr: ast::RangeExpr, errors: &mut Vec<SyntaxError>) {
         ));
     }
 }
+
+fn validate_crate_keyword_in_path_segment(
+    segment: ast::PathSegment,
+    errors: &mut Vec<SyntaxError>,
+) {
+    const ERR_MSG: &str = "The `crate` keyword is only allowed as the first segment of a path";
+
+    let crate_token = match segment.crate_token() {
+        None => return,
+        Some(it) => it,
+    };
+
+    // Disallow both ::crate and foo::crate
+    let path = segment.parent_path();
+    if segment.coloncolon_token().is_some() || path.qualifier().is_some() {
+        errors.push(SyntaxError::new(ERR_MSG, crate_token.text_range()));
+        return;
+    }
+
+    // We now know that the path variable describes a complete path.
+    // For expressions and types, validation is complete, but we still have
+    // to handle UseItems like this:
+    //      use foo:{crate};
+    // so we crawl upwards looking for any preceding paths on `UseTree`s
+    for node in path.syntax().ancestors().skip(1) {
+        match_ast! {
+            match node {
+                ast::UseTree(it) => if let Some(tree_path) = it.path() {
+                    if tree_path != path {
+                        errors.push(SyntaxError::new(ERR_MSG, crate_token.text_range()));
+                    }
+                },
+                ast::UseTreeList(_it) => continue,
+                _ => return,
+            }
+        };
+    }
+}