3 files changed, 234 insertions, 33 deletions

diff --git a/crates/ra_editor/src/code_actions.rs b/crates/ra_editor/src/code_actions.rs
index bc0e120d3..6979251d1 100644
--- a/crates/ra_editor/src/code_actions.rs
+++ b/crates/ra_editor/src/code_actions.rs
@@ -4,7 +4,7 @@ use ra_syntax::{
     algo::{find_covering_node, find_leaf_at_offset},
     ast::{self, AstNode, AttrsOwner, NameOwner, TypeParamsOwner},
     Direction, SourceFileNode,
-    SyntaxKind::{COMMA, WHITESPACE},
+    SyntaxKind::{COMMA, WHITESPACE, COMMENT},
     SyntaxNodeRef, TextRange, TextUnit,
 };
 
@@ -41,7 +41,8 @@ pub fn add_derive<'a>(
     offset: TextUnit,
 ) -> Option<impl FnOnce() -> LocalEdit + 'a> {
     let nominal = find_node_at_offset::<ast::NominalDef>(file.syntax(), offset)?;
-    Some(move || {
+    let node_start = derive_insertion_offset(nominal)?;
+    return Some(move || {
         let derive_attr = nominal
             .attrs()
             .filter_map(|x| x.as_call())
@@ -51,7 +52,6 @@ pub fn add_derive<'a>(
         let mut edit = EditBuilder::new();
         let offset = match derive_attr {
             None => {
-                let node_start = nominal.syntax().range().start();
                 edit.insert(node_start, "#[derive()]\n".to_string());
                 node_start + TextUnit::of_str("#[derive(")
             }
@@ -61,7 +61,16 @@ pub fn add_derive<'a>(
             edit: edit.finish(),
             cursor_position: Some(offset),
         }
-    })
+    });
+
+    // Insert `derive` after doc comments.
+    fn derive_insertion_offset(nominal: ast::NominalDef) -> Option<TextUnit> {
+        let non_ws_child = nominal
+            .syntax()
+            .children()
+            .find(|it| it.kind() != COMMENT && it.kind() != WHITESPACE)?;
+        Some(non_ws_child.range().start())
+    }
 }
 
 pub fn add_impl<'a>(
@@ -186,7 +195,7 @@ mod tests {
     }
 
     #[test]
-    fn test_add_derive() {
+    fn add_derive_new() {
         check_action(
             "struct Foo { a: i32, <|>}",
             "#[derive(<|>)]\nstruct Foo { a: i32, }",
@@ -197,6 +206,10 @@ mod tests {
             "#[derive(<|>)]\nstruct Foo {  a: i32, }",
             |file, off| add_derive(file, off).map(|f| f()),
         );
+    }
+
+    #[test]
+    fn add_derive_existing() {
         check_action(
             "#[derive(Clone)]\nstruct Foo { a: i32<|>, }",
             "#[derive(Clone<|>)]\nstruct Foo { a: i32, }",
@@ -205,6 +218,24 @@ mod tests {
     }
 
     #[test]
+    fn add_derive_new_with_doc_comment() {
+        check_action(
+            "
+/// `Foo` is a pretty important struct.
+/// It does stuff.
+struct Foo { a: i32<|>, }
+            ",
+            "
+/// `Foo` is a pretty important struct.
+/// It does stuff.
+#[derive(<|>)]
+struct Foo { a: i32, }
+            ",
+            |file, off| add_derive(file, off).map(|f| f()),
+        );
+    }
+
+    #[test]
     fn test_add_impl() {
         check_action(
             "struct Foo {<|>}\n",
diff --git a/crates/ra_editor/src/lib.rs b/crates/ra_editor/src/lib.rs
index ff4e8303d..c6b116159 100644
--- a/crates/ra_editor/src/lib.rs
+++ b/crates/ra_editor/src/lib.rs
@@ -148,12 +148,7 @@ pub fn find_node_at_offset<'a, N: AstNode<'a>>(
     syntax: SyntaxNodeRef<'a>,
     offset: TextUnit,
 ) -> Option<N> {
-    let leaves = find_leaf_at_offset(syntax, offset);
-    let leaf = leaves
-        .clone()
-        .find(|leaf| !leaf.kind().is_trivia())
-        .or_else(|| leaves.right_biased())?;
-    leaf.ancestors().filter_map(N::cast).next()
+    find_leaf_at_offset(syntax, offset).find_map(|leaf| leaf.ancestors().find_map(N::cast))
 }
 
 #[cfg(test)]
diff --git a/crates/ra_editor/src/line_index.rs b/crates/ra_editor/src/line_index.rs
index 9abbb0d09..aab7e4081 100644
--- a/crates/ra_editor/src/line_index.rs
+++ b/crates/ra_editor/src/line_index.rs
@@ -1,43 +1,124 @@
 use crate::TextUnit;
+use rustc_hash::FxHashMap;
 use superslice::Ext;
 
-#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+#[derive(Clone, Debug, PartialEq, Eq)]
 pub struct LineIndex {
     newlines: Vec<TextUnit>,
+    utf16_lines: FxHashMap<u32, Vec<Utf16Char>>,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub struct LineCol {
     pub line: u32,
-    pub col: TextUnit,
+    pub col_utf16: u32,
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+struct Utf16Char {
+    start: TextUnit,
+    end: TextUnit,
+}
+
+impl Utf16Char {
+    fn len(&self) -> TextUnit {
+        self.end - self.start
+    }
 }
 
 impl LineIndex {
     pub fn new(text: &str) -> LineIndex {
+        let mut utf16_lines = FxHashMap::default();
+        let mut utf16_chars = Vec::new();
+
         let mut newlines = vec![0.into()];
-        let mut curr = 0.into();
+        let mut curr_row = 0.into();
+        let mut curr_col = 0.into();
+        let mut line = 0;
         for c in text.chars() {
-            curr += TextUnit::of_char(c);
+            curr_row += TextUnit::of_char(c);
             if c == '\n' {
-                newlines.push(curr);
+                newlines.push(curr_row);
+
+                // Save any utf-16 characters seen in the previous line
+                if utf16_chars.len() > 0 {
+                    utf16_lines.insert(line, utf16_chars);
+                    utf16_chars = Vec::new();
+                }
+
+                // Prepare for processing the next line
+                curr_col = 0.into();
+                line += 1;
+                continue;
             }
+
+            let char_len = TextUnit::of_char(c);
+            if char_len.to_usize() > 1 {
+                utf16_chars.push(Utf16Char {
+                    start: curr_col,
+                    end: curr_col + char_len,
+                });
+            }
+
+            curr_col += char_len;
+        }
+        LineIndex {
+            newlines,
+            utf16_lines,
         }
-        LineIndex { newlines }
     }
 
     pub fn line_col(&self, offset: TextUnit) -> LineCol {
         let line = self.newlines.upper_bound(&offset) - 1;
         let line_start_offset = self.newlines[line];
         let col = offset - line_start_offset;
+
         LineCol {
             line: line as u32,
-            col,
+            col_utf16: self.utf8_to_utf16_col(line as u32, col) as u32,
         }
     }
 
     pub fn offset(&self, line_col: LineCol) -> TextUnit {
         //TODO: return Result
-        self.newlines[line_col.line as usize] + line_col.col
+        let col = self.utf16_to_utf8_col(line_col.line, line_col.col_utf16);
+        self.newlines[line_col.line as usize] + col
+    }
+
+    fn utf8_to_utf16_col(&self, line: u32, mut col: TextUnit) -> usize {
+        if let Some(utf16_chars) = self.utf16_lines.get(&line) {
+            let mut correction = TextUnit::from_usize(0);
+            for c in utf16_chars {
+                if col >= c.end {
+                    correction += c.len() - TextUnit::from_usize(1);
+                } else {
+                    // From here on, all utf16 characters come *after* the character we are mapping,
+                    // so we don't need to take them into account
+                    break;
+                }
+            }
+
+            col -= correction;
+        }
+
+        col.to_usize()
+    }
+
+    fn utf16_to_utf8_col(&self, line: u32, col: u32) -> TextUnit {
+        let mut col: TextUnit = col.into();
+        if let Some(utf16_chars) = self.utf16_lines.get(&line) {
+            for c in utf16_chars {
+                if col >= c.start {
+                    col += c.len() - TextUnit::from_usize(1);
+                } else {
+                    // From here on, all utf16 characters come *after* the character we are mapping,
+                    // so we don't need to take them into account
+                    break;
+                }
+            }
+        }
+
+        col
     }
 }
 
@@ -49,63 +130,63 @@ fn test_line_index() {
         index.line_col(0.into()),
         LineCol {
             line: 0,
-            col: 0.into()
+            col_utf16: 0
         }
     );
     assert_eq!(
         index.line_col(1.into()),
         LineCol {
             line: 0,
-            col: 1.into()
+            col_utf16: 1
         }
     );
     assert_eq!(
         index.line_col(5.into()),
         LineCol {
             line: 0,
-            col: 5.into()
+            col_utf16: 5
         }
     );
     assert_eq!(
         index.line_col(6.into()),
         LineCol {
             line: 1,
-            col: 0.into()
+            col_utf16: 0
         }
     );
     assert_eq!(
         index.line_col(7.into()),
         LineCol {
             line: 1,
-            col: 1.into()
+            col_utf16: 1
         }
     );
     assert_eq!(
         index.line_col(8.into()),
         LineCol {
             line: 1,
-            col: 2.into()
+            col_utf16: 2
         }
     );
     assert_eq!(
         index.line_col(10.into()),
         LineCol {
             line: 1,
-            col: 4.into()
+            col_utf16: 4
         }
     );
     assert_eq!(
         index.line_col(11.into()),
         LineCol {
             line: 1,
-            col: 5.into()
+            col_utf16: 5
         }
     );
     assert_eq!(
         index.line_col(12.into()),
         LineCol {
             line: 1,
-            col: 6.into()
+            col_utf16: 6
         }
     );
 
@@ -115,35 +196,129 @@ fn test_line_index() {
         index.line_col(0.into()),
         LineCol {
             line: 0,
-            col: 0.into()
+            col_utf16: 0
         }
     );
     assert_eq!(
         index.line_col(1.into()),
         LineCol {
             line: 1,
-            col: 0.into()
+            col_utf16: 0
         }
     );
     assert_eq!(
         index.line_col(2.into()),
         LineCol {
             line: 1,
-            col: 1.into()
+            col_utf16: 1
         }
     );
     assert_eq!(
         index.line_col(6.into()),
         LineCol {
             line: 1,
-            col: 5.into()
+            col_utf16: 5
         }
     );
     assert_eq!(
         index.line_col(7.into()),
         LineCol {
             line: 2,
-            col: 0.into()
+            col_utf16: 0
         }
     );
 }
+
+#[cfg(test)]
+mod test_utf8_utf16_conv {
+    use super::*;
+
+    #[test]
+    fn test_char_len() {
+        assert_eq!('メ'.len_utf8(), 3);
+        assert_eq!('メ'.len_utf16(), 1);
+    }
+
+    #[test]
+    fn test_empty_index() {
+        let col_index = LineIndex::new(
+            "
+const C: char = 'x';
+",
+        );
+        assert_eq!(col_index.utf16_lines.len(), 0);
+    }
+
+    #[test]
+    fn test_single_char() {
+        let col_index = LineIndex::new(
+            "
+const C: char = 'メ';
+",
+        );
+
+        assert_eq!(col_index.utf16_lines.len(), 1);
+        assert_eq!(col_index.utf16_lines[&1].len(), 1);
+        assert_eq!(
+            col_index.utf16_lines[&1][0],
+            Utf16Char {
+                start: 17.into(),
+                end: 20.into()
+            }
+        );
+
+        // UTF-8 to UTF-16, no changes
+        assert_eq!(col_index.utf8_to_utf16_col(1, 15.into()), 15);
+
+        // UTF-8 to UTF-16
+        assert_eq!(col_index.utf8_to_utf16_col(1, 22.into()), 20);
+
+        // UTF-16 to UTF-8, no changes
+        assert_eq!(col_index.utf16_to_utf8_col(1, 15), TextUnit::from(15));
+
+        // UTF-16 to UTF-8
+        assert_eq!(col_index.utf16_to_utf8_col(1, 19), TextUnit::from(21));
+    }
+
+    #[test]
+    fn test_string() {
+        let col_index = LineIndex::new(
+            "
+const C: char = \"メ メ\";
+",
+        );
+
+        assert_eq!(col_index.utf16_lines.len(), 1);
+        assert_eq!(col_index.utf16_lines[&1].len(), 2);
+        assert_eq!(
+            col_index.utf16_lines[&1][0],
+            Utf16Char {
+                start: 17.into(),
+                end: 20.into()
+            }
+        );
+        assert_eq!(
+            col_index.utf16_lines[&1][1],
+            Utf16Char {
+                start: 21.into(),
+                end: 24.into()
+            }
+        );
+
+        // UTF-8 to UTF-16
+        assert_eq!(col_index.utf8_to_utf16_col(1, 15.into()), 15);
+
+        assert_eq!(col_index.utf8_to_utf16_col(1, 21.into()), 19);
+        assert_eq!(col_index.utf8_to_utf16_col(1, 25.into()), 21);
+
+        assert!(col_index.utf8_to_utf16_col(2, 15.into()) == 15);
+
+        // UTF-16 to UTF-8
+        assert_eq!(col_index.utf16_to_utf8_col(1, 15), TextUnit::from_usize(15));
+
+        assert_eq!(col_index.utf16_to_utf8_col(1, 18), TextUnit::from_usize(20));
+        assert_eq!(col_index.utf16_to_utf8_col(1, 19), TextUnit::from_usize(23));
+
+        assert_eq!(col_index.utf16_to_utf8_col(2, 15), TextUnit::from_usize(15));
+    }
+}