23 files changed, 258 insertions, 122 deletions

diff --git a/crates/ra_analysis/Cargo.toml b/crates/ra_analysis/Cargo.toml
index a30cdfc9c..a82e1761c 100644
--- a/crates/ra_analysis/Cargo.toml
+++ b/crates/ra_analysis/Cargo.toml
@@ -15,6 +15,7 @@ im = "12.0.0"
 ra_syntax = { path = "../ra_syntax" }
 ra_editor = { path = "../ra_editor" }
 salsa = { path = "../salsa" }
+rustc-hash = "1.0"
 
 [dev-dependencies]
 test_utils = { path = "../test_utils" }
diff --git a/crates/ra_analysis/src/db/imp.rs b/crates/ra_analysis/src/db/imp.rs
index f26be1046..36f6cf290 100644
--- a/crates/ra_analysis/src/db/imp.rs
+++ b/crates/ra_analysis/src/db/imp.rs
@@ -2,9 +2,10 @@ use std::{
     sync::Arc,
     any::Any,
     hash::{Hash, Hasher},
-    collections::hash_map::{DefaultHasher, HashMap},
+    collections::hash_map::{DefaultHasher},
     iter,
 };
+use rustc_hash::FxHashMap;
 use salsa;
 use {FileId, imp::FileResolverImp};
 use super::{State, Query, QueryCtx};
@@ -13,7 +14,7 @@ pub(super) type Data = Arc<Any + Send + Sync + 'static>;
 
 #[derive(Debug)]
 pub(super) struct Db {
-    names: Arc<HashMap<salsa::QueryTypeId, &'static str>>,
+    names: Arc<FxHashMap<salsa::QueryTypeId, &'static str>>,
     pub(super) imp: salsa::Db<State, Data>,
 }
 
@@ -85,7 +86,7 @@ where
 
 pub(super) struct QueryRegistry {
     config: Option<salsa::QueryConfig<State, Data>>,
-    names: HashMap<salsa::QueryTypeId, &'static str>,
+    names: FxHashMap<salsa::QueryTypeId, &'static str>,
 }
 
 impl QueryRegistry {
@@ -109,7 +110,7 @@ impl QueryRegistry {
                 (Arc::new(res), fingerprint)
             })
         );
-        let mut names = HashMap::new();
+        let mut names = FxHashMap::default();
         names.insert(FILE_TEXT, "FILE_TEXT");
         names.insert(FILE_SET, "FILE_SET");
         QueryRegistry { config: Some(config), names }
diff --git a/crates/ra_analysis/src/imp.rs b/crates/ra_analysis/src/imp.rs
index 517867e86..47bc0032b 100644
--- a/crates/ra_analysis/src/imp.rs
+++ b/crates/ra_analysis/src/imp.rs
@@ -4,11 +4,12 @@ use std::{
         atomic::{AtomicBool, Ordering::SeqCst},
     },
     fmt,
-    collections::{HashSet, VecDeque},
+    collections::VecDeque,
     iter,
 };
 
 use relative_path::RelativePath;
+use rustc_hash::FxHashSet;
 use ra_editor::{self, FileSymbol, LineIndex, find_node_at_offset, LocalEdit, resolve_local_name};
 use ra_syntax::{
     TextUnit, TextRange, SmolStr, File, AstNode,
@@ -84,7 +85,7 @@ impl AnalysisHostImpl {
         data.root = Arc::new(data.root.apply_changes(&mut iter::empty(), Some(resolver)));
     }
     pub fn set_crate_graph(&mut self, graph: CrateGraph) {
-        let mut visited = HashSet::new();
+        let mut visited = FxHashSet::default();
         for &file_id in graph.crate_roots.values() {
             if !visited.insert(file_id) {
                 panic!("duplicate crate root: {:?}", file_id);
@@ -168,7 +169,7 @@ impl AnalysisImpl {
         let mut res = Vec::new();
         let mut work = VecDeque::new();
         work.push_back(file_id);
-        let mut visited = HashSet::new();
+        let mut visited = FxHashSet::default();
         while let Some(id) = work.pop_front() {
             if let Some(crate_id) = crate_graph.crate_id_for_crate_root(id) {
                 res.push(crate_id);
diff --git a/crates/ra_analysis/src/lib.rs b/crates/ra_analysis/src/lib.rs
index f6ceb7eb2..849fd93e4 100644
--- a/crates/ra_analysis/src/lib.rs
+++ b/crates/ra_analysis/src/lib.rs
@@ -11,6 +11,7 @@ extern crate relative_path;
 extern crate crossbeam_channel;
 extern crate im;
 extern crate salsa;
+extern crate rustc_hash;
 
 mod symbol_index;
 mod module_map;
@@ -23,13 +24,13 @@ mod descriptors;
 
 use std::{
     sync::Arc,
-    collections::HashMap,
     fmt::Debug,
 };
 
 use relative_path::{RelativePath, RelativePathBuf};
 use ra_syntax::{File, TextRange, TextUnit, AtomEdit};
 use imp::{AnalysisImpl, AnalysisHostImpl, FileResolverImp};
+use rustc_hash::FxHashMap;
 
 pub use ra_editor::{
     StructureNode, LineIndex, FileSymbol,
@@ -46,7 +47,7 @@ pub struct CrateId(pub u32);
 
 #[derive(Debug, Clone, Default)]
 pub struct CrateGraph {
-    pub crate_roots: HashMap<CrateId, FileId>,
+    pub crate_roots: FxHashMap<CrateId, FileId>,
 }
 
 pub trait FileResolver: Debug + Send + Sync + 'static {
diff --git a/crates/ra_analysis/src/roots.rs b/crates/ra_analysis/src/roots.rs
index 1835a9b25..32a8c5bd0 100644
--- a/crates/ra_analysis/src/roots.rs
+++ b/crates/ra_analysis/src/roots.rs
@@ -1,11 +1,11 @@
 use std::{
-    collections::HashMap,
     sync::Arc,
     panic,
 };
 
 use once_cell::sync::OnceCell;
 use rayon::prelude::*;
+use rustc_hash::FxHashMap;
 use ra_editor::LineIndex;
 use ra_syntax::File;
 
@@ -118,7 +118,7 @@ impl FileData {
 #[derive(Debug)]
 pub(crate) struct ReadonlySourceRoot {
     symbol_index: Arc<SymbolIndex>,
-    file_map: HashMap<FileId, FileData>,
+    file_map: FxHashMap<FileId, FileData>,
     module_tree: Arc<ModuleTreeDescriptor>,
 }
 
@@ -139,7 +139,7 @@ impl ReadonlySourceRoot {
         let symbol_index = SymbolIndex::for_files(
             modules.par_iter().map(|it| (it.0, it.1.clone()))
         );
-        let file_map: HashMap<FileId, FileData> = files
+        let file_map: FxHashMap<FileId, FileData> = files
             .into_iter()
             .map(|(id, text)| (id, FileData::new(text)))
             .collect();
diff --git a/crates/ra_analysis/tests/tests.rs b/crates/ra_analysis/tests/tests.rs
index 334dc5e48..a886cd0ff 100644
--- a/crates/ra_analysis/tests/tests.rs
+++ b/crates/ra_analysis/tests/tests.rs
@@ -1,12 +1,13 @@
 extern crate relative_path;
 extern crate ra_analysis;
+extern crate rustc_hash;
 extern crate test_utils;
 
 use std::{
     sync::Arc,
-    collections::HashMap,
 };
 
+use rustc_hash::FxHashMap;
 use relative_path::{RelativePath, RelativePathBuf};
 use ra_analysis::{Analysis, AnalysisHost, FileId, FileResolver, JobHandle, CrateGraph, CrateId};
 use test_utils::assert_eq_dbg;
@@ -131,7 +132,7 @@ fn test_resolve_crate_root() {
 
     let crate_graph = CrateGraph {
         crate_roots: {
-            let mut m = HashMap::new();
+            let mut m = FxHashMap::default();
             m.insert(CrateId(1), FileId(1));
             m
         },
diff --git a/crates/ra_editor/Cargo.toml b/crates/ra_editor/Cargo.toml
index 40e3254ff..91cefc8d7 100644
--- a/crates/ra_editor/Cargo.toml
+++ b/crates/ra_editor/Cargo.toml
@@ -8,6 +8,7 @@ publish = false
 itertools = "0.7.8"
 superslice = "0.1.0"
 join_to_string = "0.1.1"
+rustc-hash = "1.0"
 
 ra_syntax = { path = "../ra_syntax" }
 
diff --git a/crates/ra_editor/src/completion.rs b/crates/ra_editor/src/completion.rs
index 570d72d66..20b8484b3 100644
--- a/crates/ra_editor/src/completion.rs
+++ b/crates/ra_editor/src/completion.rs
@@ -1,4 +1,4 @@
-use std::collections::{HashSet, HashMap};
+use rustc_hash::{FxHashMap, FxHashSet};
 
 use ra_syntax::{
     File, TextUnit, AstNode, SyntaxNodeRef, SyntaxKind::*,
@@ -96,7 +96,7 @@ fn complete_name_ref(file: &File, name_ref: ast::NameRef, acc: &mut Vec<Completi
 }
 
 fn param_completions(ctx: SyntaxNodeRef, acc: &mut Vec<CompletionItem>) {
-    let mut params = HashMap::new();
+    let mut params = FxHashMap::default();
     for node in ctx.ancestors() {
         let _ = visitor_ctx(&mut params)
             .visit::<ast::Root, _>(process)
@@ -114,7 +114,7 @@ fn param_completions(ctx: SyntaxNodeRef, acc: &mut Vec<CompletionItem>) {
             })
         });
 
-    fn process<'a, N: ast::FnDefOwner<'a>>(node: N, params: &mut HashMap<String, (u32, ast::Param<'a>)>) {
+    fn process<'a, N: ast::FnDefOwner<'a>>(node: N, params: &mut FxHashMap<String, (u32, ast::Param<'a>)>) {
         node.functions()
             .filter_map(|it| it.param_list())
             .flat_map(|it| it.params())
@@ -232,7 +232,7 @@ fn complete_mod_item_snippets(acc: &mut Vec<CompletionItem>) {
 }
 
 fn complete_fn(name_ref: ast::NameRef, scopes: &FnScopes, acc: &mut Vec<CompletionItem>) {
-    let mut shadowed = HashSet::new();
+    let mut shadowed = FxHashSet::default();
     acc.extend(
         scopes.scope_chain(name_ref.syntax())
             .flat_map(|scope| scopes.entries(scope).iter())
diff --git a/crates/ra_editor/src/folding_ranges.rs b/crates/ra_editor/src/folding_ranges.rs
index 733512368..3aabd54ae 100644
--- a/crates/ra_editor/src/folding_ranges.rs
+++ b/crates/ra_editor/src/folding_ranges.rs
@@ -1,4 +1,4 @@
-use std::collections::HashSet;
+use rustc_hash::FxHashSet;
 
 use ra_syntax::{
     File, TextRange, SyntaxNodeRef,
@@ -20,7 +20,7 @@ pub struct Fold {
 
 pub fn folding_ranges(file: &File) -> Vec<Fold> {
     let mut res = vec![];
-    let mut visited = HashSet::new();
+    let mut visited = FxHashSet::default();
 
     for node in file.syntax().descendants() {
         if visited.contains(&node) {
@@ -56,7 +56,7 @@ pub fn folding_ranges(file: &File) -> Vec<Fold> {
 fn contiguous_range_for<'a>(
     kind: SyntaxKind,
     node: SyntaxNodeRef<'a>,
-    visited: &mut HashSet<SyntaxNodeRef<'a>>,
+    visited: &mut FxHashSet<SyntaxNodeRef<'a>>,
 ) -> Option<TextRange> {
     visited.insert(node);
 
diff --git a/crates/ra_editor/src/lib.rs b/crates/ra_editor/src/lib.rs
index fe0045378..710afc65d 100644
--- a/crates/ra_editor/src/lib.rs
+++ b/crates/ra_editor/src/lib.rs
@@ -2,6 +2,7 @@ extern crate ra_syntax;
 extern crate superslice;
 extern crate itertools;
 extern crate join_to_string;
+extern crate rustc_hash;
 #[cfg(test)]
 #[macro_use]
 extern crate test_utils as _test_utils;
@@ -88,7 +89,6 @@ pub fn highlight(file: &File) -> Vec<HighlightedRange> {
     let mut res = Vec::new();
     for node in file.syntax().descendants() {
         let tag = match node.kind() {
-            ERROR => "error",
             COMMENT | DOC_COMMENT => "comment",
             STRING | RAW_STRING | RAW_BYTE_STRING | BYTE_STRING => "string",
             ATTR => "attribute",
@@ -108,21 +108,10 @@ pub fn highlight(file: &File) -> Vec<HighlightedRange> {
 }
 
 pub fn diagnostics(file: &File) -> Vec<Diagnostic> {
-    let mut res = Vec::new();
-
-    for node in file.syntax().descendants() {
-        if node.kind() == ERROR {
-            res.push(Diagnostic {
-                range: node.range(),
-                msg: "Syntax Error".to_string(),
-            });
-        }
-    }
-    res.extend(file.errors().into_iter().map(|err| Diagnostic {
+    file.errors().into_iter().map(|err| Diagnostic {
         range: TextRange::offset_len(err.offset, 1.into()),
-        msg: err.msg,
-    }));
-    res
+        msg: "Syntax Error: ".to_string() + &err.msg,
+    }).collect()
 }
 
 pub fn syntax_tree(file: &File) -> String {
diff --git a/crates/ra_editor/src/scope/fn_scope.rs b/crates/ra_editor/src/scope/fn_scope.rs
index 65d85279f..9a48bda02 100644
--- a/crates/ra_editor/src/scope/fn_scope.rs
+++ b/crates/ra_editor/src/scope/fn_scope.rs
@@ -1,7 +1,5 @@
-use std::{
-    fmt,
-    collections::HashMap,
-};
+use std::fmt;
+use rustc_hash::FxHashMap;
 
 use ra_syntax::{
     SyntaxNodeRef, SyntaxNode, SmolStr, AstNode,
@@ -15,7 +13,7 @@ type ScopeId = usize;
 pub struct FnScopes {
     pub self_param: Option<SyntaxNode>,
     scopes: Vec<ScopeData>,
-    scope_for: HashMap<SyntaxNode, ScopeId>,
+    scope_for: FxHashMap<SyntaxNode, ScopeId>,
 }
 
 impl FnScopes {
@@ -25,7 +23,7 @@ impl FnScopes {
                 .and_then(|it| it.self_param())
                 .map(|it| it.syntax().owned()),
             scopes: Vec::new(),
-            scope_for: HashMap::new()
+            scope_for: FxHashMap::default()
         };
         let root = scopes.root_scope();
         scopes.add_params_bindings(root, fn_def.param_list());
@@ -242,9 +240,9 @@ struct ScopeData {
 }
 
 pub fn resolve_local_name<'a>(name_ref: ast::NameRef, scopes: &'a FnScopes) -> Option<&'a ScopeEntry> {
-    use std::collections::HashSet;
+    use rustc_hash::FxHashSet;
 
-    let mut shadowed = HashSet::new();
+    let mut shadowed = FxHashSet::default();
     let ret = scopes.scope_chain(name_ref.syntax())
         .flat_map(|scope| scopes.entries(scope).iter())
         .filter(|entry| shadowed.insert(entry.name()))
diff --git a/crates/ra_editor/src/typing.rs b/crates/ra_editor/src/typing.rs
index 3384389d1..1dc658f9b 100644
--- a/crates/ra_editor/src/typing.rs
+++ b/crates/ra_editor/src/typing.rs
@@ -30,6 +30,7 @@ pub fn join_lines(file: &File, range: TextRange) -> LocalEdit {
     } else {
         range
     };
+
     let node = find_covering_node(file.syntax(), range);
     let mut edit = EditBuilder::new();
     for node in node.descendants() {
@@ -57,14 +58,19 @@ pub fn join_lines(file: &File, range: TextRange) -> LocalEdit {
 }
 
 pub fn on_enter(file: &File, offset: TextUnit) -> Option<LocalEdit> {
-    let comment = find_leaf_at_offset(file.syntax(), offset).left_biased().filter(|it| it.kind() == COMMENT)?;
-    let prefix = comment_preffix(comment)?;
-    if offset < comment.range().start() + TextUnit::of_str(prefix) {
+    let comment = find_leaf_at_offset(file.syntax(), offset).left_biased().and_then(|it| ast::Comment::cast(it))?;
+
+    if let ast::CommentFlavor::Multiline = comment.flavor() {
+        return None;
+    }
+
+    let prefix = comment.prefix();
+    if offset < comment.syntax().range().start() + TextUnit::of_str(prefix) + TextUnit::from(1) {
         return None;
     }
 
-    let indent = node_indent(file, comment)?;
-    let inserted = format!("\n{}{}", indent, prefix);
+    let indent = node_indent(file, comment.syntax())?;
+    let inserted = format!("\n{}{} ", indent, prefix);
     let cursor_position = offset + TextUnit::of_str(&inserted);
     let mut edit = EditBuilder::new();
     edit.insert(offset, inserted);
@@ -74,20 +80,6 @@ pub fn on_enter(file: &File, offset: TextUnit) -> Option<LocalEdit> {
     })
 }
 
-fn comment_preffix(comment: SyntaxNodeRef) -> Option<&'static str> {
-    let text = comment.leaf_text().unwrap();
-    let res = if text.starts_with("///") {
-        "/// "
-    } else if text.starts_with("//!") {
-        "//! "
-    } else if text.starts_with("//") {
-        "// "
-    } else {
-        return None;
-    };
-    Some(res)
-}
-
 fn node_indent<'a>(file: &'a File, node: SyntaxNodeRef) -> Option<&'a str> {
     let ws = match find_leaf_at_offset(file.syntax(), node.range().start()) {
         LeafAtOffset::Between(l, r) => {
@@ -139,41 +131,60 @@ fn remove_newline(
     node_text: &str,
     offset: TextUnit,
 ) {
-    if node.kind() == WHITESPACE && node_text.bytes().filter(|&b| b == b'\n').count() == 1 {
-        if join_single_expr_block(edit, node).is_some() {
-            return
-        }
-        match (node.prev_sibling(), node.next_sibling()) {
-            (Some(prev), Some(next)) => {
-                let range = TextRange::from_to(prev.range().start(), node.range().end());
-                if is_trailing_comma(prev.kind(), next.kind()) {
-                    edit.delete(range);
-                } else if no_space_required(prev.kind(), next.kind()) {
-                    edit.delete(node.range());
-                } else if prev.kind() == COMMA && next.kind() == R_CURLY {
-                    edit.replace(range, " ".to_string());
-                } else {
-                    edit.replace(
-                        node.range(),
-                        compute_ws(prev, next).to_string(),
-                    );
-                }
-                return;
-            }
-            _ => (),
-        }
+    if node.kind() != WHITESPACE || node_text.bytes().filter(|&b| b == b'\n').count() != 1 {
+        // The node is either the first or the last in the file
+        let suff = &node_text[TextRange::from_to(
+            offset - node.range().start() + TextUnit::of_char('\n'),
+            TextUnit::of_str(node_text),
+        )];
+        let spaces = suff.bytes().take_while(|&b| b == b' ').count();
+
+        edit.replace(
+            TextRange::offset_len(offset, ((spaces + 1) as u32).into()),
+            " ".to_string(),
+        );
+        return;
     }
 
-    let suff = &node_text[TextRange::from_to(
-        offset - node.range().start() + TextUnit::of_char('\n'),
-        TextUnit::of_str(node_text),
-    )];
-    let spaces = suff.bytes().take_while(|&b| b == b' ').count();
+    // Special case that turns something like:
+    //
+    // ```
+    // my_function({<|>
+    //    <some-expr>
+    // })
+    // ```
+    //
+    // into `my_function(<some-expr>)`
+    if join_single_expr_block(edit, node).is_some() {
+        return
+    }
 
-    edit.replace(
-        TextRange::offset_len(offset, ((spaces + 1) as u32).into()),
-        " ".to_string(),
-    );
+    // The node is between two other nodes
+    let prev = node.prev_sibling().unwrap();
+    let next = node.next_sibling().unwrap();
+    if is_trailing_comma(prev.kind(), next.kind()) {
+        // Removes: trailing comma, newline (incl. surrounding whitespace)
+        edit.delete(TextRange::from_to(prev.range().start(), node.range().end()));
+    } else if prev.kind() == COMMA && next.kind() == R_CURLY {
+        // Removes: comma, newline (incl. surrounding whitespace)
+        // Adds: a single whitespace
+        edit.replace(
+            TextRange::from_to(prev.range().start(), node.range().end()),
+            " ".to_string()
+        );
+    } else if let (Some(_), Some(next)) = (ast::Comment::cast(prev), ast::Comment::cast(next)) {
+        // Removes: newline (incl. surrounding whitespace), start of the next comment
+        edit.delete(TextRange::from_to(
+            node.range().start(),
+            next.syntax().range().start() + TextUnit::of_str(next.prefix())
+        ));
+    } else {
+        // Remove newline but add a computed amount of whitespace characters
+        edit.replace(
+            node.range(),
+            compute_ws(prev, next).to_string(),
+        );
+    }
 }
 
 fn is_trailing_comma(left: SyntaxKind, right: SyntaxKind) -> bool {
@@ -183,13 +194,6 @@ fn is_trailing_comma(left: SyntaxKind, right: SyntaxKind) -> bool {
     }
 }
 
-fn no_space_required(left: SyntaxKind, right: SyntaxKind) -> bool {
-    match (left, right) {
-       (_, DOT) => true,
-        _ => false
-    }
-}
-
 fn join_single_expr_block(
     edit: &mut EditBuilder,
     node: SyntaxNodeRef,
@@ -231,6 +235,7 @@ fn compute_ws(left: SyntaxNodeRef, right: SyntaxNodeRef) -> &'static str {
     }
     match right.kind() {
         R_PAREN | R_BRACK => return "",
+        DOT => return "",
         _ => (),
     }
     " "
@@ -291,6 +296,80 @@ fn foo() {
 }");
     }
 
+    #[test]
+    fn test_join_lines_normal_comments() {
+        check_join_lines(r"
+fn foo() {
+    // Hello<|>
+    // world!
+}
+", r"
+fn foo() {
+    // Hello<|> world!
+}
+");
+    }
+
+    #[test]
+    fn test_join_lines_doc_comments() {
+        check_join_lines(r"
+fn foo() {
+    /// Hello<|>
+    /// world!
+}
+", r"
+fn foo() {
+    /// Hello<|> world!
+}
+");
+    }
+
+    #[test]
+    fn test_join_lines_mod_comments() {
+        check_join_lines(r"
+fn foo() {
+    //! Hello<|>
+    //! world!
+}
+", r"
+fn foo() {
+    //! Hello<|> world!
+}
+");
+    }
+
+    #[test]
+    fn test_join_lines_multiline_comments_1() {
+        check_join_lines(r"
+fn foo() {
+    // Hello<|>
+    /* world! */
+}
+", r"
+fn foo() {
+    // Hello<|> world! */
+}
+");
+    }
+
+    #[test]
+    fn test_join_lines_multiline_comments_2() {
+        check_join_lines(r"
+fn foo() {
+    // The<|>
+    /* quick
+    brown
+    fox! */
+}
+", r"
+fn foo() {
+    // The<|> quick
+    brown
+    fox! */
+}
+");
+    }
+
     fn check_join_lines_sel(before: &str, after: &str) {
         let (sel, before) = extract_range(before);
         let file = File::parse(&before);
diff --git a/crates/ra_lsp_server/Cargo.toml b/crates/ra_lsp_server/Cargo.toml
index 32463e499..1fe6b2ebe 100644
--- a/crates/ra_lsp_server/Cargo.toml
+++ b/crates/ra_lsp_server/Cargo.toml
@@ -21,6 +21,7 @@ im = "12.0.0"
 cargo_metadata = "0.6.0"
 text_unit = { version = "0.1.2", features = ["serde"] }
 smol_str = { version = "0.1.5", features = ["serde"] }
+rustc-hash = "1.0"
 
 ra_syntax = { path = "../ra_syntax" }
 ra_editor = { path = "../ra_editor" }
diff --git a/crates/ra_lsp_server/src/lib.rs b/crates/ra_lsp_server/src/lib.rs
index d2f76972f..60652d55e 100644
--- a/crates/ra_lsp_server/src/lib.rs
+++ b/crates/ra_lsp_server/src/lib.rs
@@ -16,6 +16,7 @@ extern crate walkdir;
 extern crate im;
 extern crate relative_path;
 extern crate cargo_metadata;
+extern crate rustc_hash;
 
 extern crate gen_lsp_server;
 extern crate ra_editor;
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 725036cc7..ab8be15e9 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -1,4 +1,4 @@
-use std::collections::{HashMap};
+use rustc_hash::FxHashMap;
 
 use languageserver_types::{
     Diagnostic, DiagnosticSeverity, DocumentSymbol,
@@ -267,7 +267,7 @@ pub fn handle_runnables(
             bin: "cargo".to_string(),
             args,
             env: {
-                let mut m = HashMap::new();
+                let mut m = FxHashMap::default();
                 m.insert(
                     "RUST_BACKTRACE".to_string(),
                     "short".to_string(),
diff --git a/crates/ra_lsp_server/src/main_loop/mod.rs b/crates/ra_lsp_server/src/main_loop/mod.rs
index 53c6f1dff..402615e42 100644
--- a/crates/ra_lsp_server/src/main_loop/mod.rs
+++ b/crates/ra_lsp_server/src/main_loop/mod.rs
@@ -3,7 +3,6 @@ mod subscriptions;
 
 use std::{
     path::PathBuf,
-    collections::{HashMap},
 };
 
 use serde::{Serialize, de::DeserializeOwned};
@@ -15,6 +14,7 @@ use gen_lsp_server::{
     RawRequest, RawNotification, RawMessage, RawResponse, ErrorCode,
     handle_shutdown,
 };
+use rustc_hash::FxHashMap;
 
 use {
     req,
@@ -50,7 +50,7 @@ pub fn main_loop(
     info!("server initialized, serving requests");
     let mut state = ServerWorldState::new();
 
-    let mut pending_requests = HashMap::new();
+    let mut pending_requests = FxHashMap::default();
     let mut subs = Subscriptions::new();
     let main_res = main_loop_inner(
         internal_mode,
@@ -95,7 +95,7 @@ fn main_loop_inner(
     fs_worker: Worker<PathBuf, (PathBuf, Vec<FileEvent>)>,
     ws_worker: Worker<PathBuf, Result<CargoWorkspace>>,
     state: &mut ServerWorldState,
-    pending_requests: &mut HashMap<u64, JobHandle>,
+    pending_requests: &mut FxHashMap<u64, JobHandle>,
     subs: &mut Subscriptions,
 ) -> Result<()> {
     let (libdata_sender, libdata_receiver) = unbounded();
@@ -213,7 +213,7 @@ fn main_loop_inner(
 fn on_task(
     task: Task,
     msg_sender: &Sender<RawMessage>,
-    pending_requests: &mut HashMap<u64, JobHandle>,
+    pending_requests: &mut FxHashMap<u64, JobHandle>,
 ) {
     match task {
         Task::Respond(response) => {
@@ -229,7 +229,7 @@ fn on_task(
 
 fn on_request(
     world: &mut ServerWorldState,
-    pending_requests: &mut HashMap<u64, JobHandle>,
+    pending_requests: &mut FxHashMap<u64, JobHandle>,
     pool: &ThreadPool,
     sender: &Sender<Task>,
     req: RawRequest,
@@ -269,7 +269,7 @@ fn on_request(
 fn on_notification(
     msg_sender: &Sender<RawMessage>,
     state: &mut ServerWorldState,
-    pending_requests: &mut HashMap<u64, JobHandle>,
+    pending_requests: &mut FxHashMap<u64, JobHandle>,
     subs: &mut Subscriptions,
     not: RawNotification,
 ) -> Result<()> {
diff --git a/crates/ra_lsp_server/src/main_loop/subscriptions.rs b/crates/ra_lsp_server/src/main_loop/subscriptions.rs
index 27f92cc9a..310153382 100644
--- a/crates/ra_lsp_server/src/main_loop/subscriptions.rs
+++ b/crates/ra_lsp_server/src/main_loop/subscriptions.rs
@@ -1,13 +1,13 @@
-use std::collections::HashSet;
+use rustc_hash::FxHashSet;
 use ra_analysis::FileId;
 
 pub struct Subscriptions {
-    subs: HashSet<FileId>,
+    subs: FxHashSet<FileId>,
 }
 
 impl Subscriptions {
     pub fn new() -> Subscriptions {
-        Subscriptions { subs: HashSet::new() }
+        Subscriptions { subs: FxHashSet::default() }
     }
     pub fn add_sub(&mut self, file_id: FileId) {
         self.subs.insert(file_id);
diff --git a/crates/ra_lsp_server/src/project_model.rs b/crates/ra_lsp_server/src/project_model.rs
index 5db34e3e5..43e4fd654 100644
--- a/crates/ra_lsp_server/src/project_model.rs
+++ b/crates/ra_lsp_server/src/project_model.rs
@@ -1,7 +1,7 @@
 use std::{
-    collections::{HashMap, HashSet},
     path::{Path, PathBuf},
 };
+use rustc_hash::{FxHashMap, FxHashSet};
 use cargo_metadata::{metadata_run, CargoOpt};
 use ra_syntax::SmolStr;
 
@@ -80,11 +80,11 @@ impl CargoWorkspace {
             true,
             Some(CargoOpt::AllFeatures)
         ).map_err(|e| format_err!("cargo metadata failed: {}", e))?;
-        let mut pkg_by_id = HashMap::new();
+        let mut pkg_by_id = FxHashMap::default();
         let mut packages = Vec::new();
         let mut targets = Vec::new();
 
-        let ws_members: HashSet<String> = meta.workspace_members
+        let ws_members: FxHashSet<String> = meta.workspace_members
             .into_iter()
             .map(|it| it.raw)
             .collect();
diff --git a/crates/ra_lsp_server/src/req.rs b/crates/ra_lsp_server/src/req.rs
index 458c79ea9..f80957589 100644
--- a/crates/ra_lsp_server/src/req.rs
+++ b/crates/ra_lsp_server/src/req.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use rustc_hash::FxHashMap;
 use languageserver_types::{TextDocumentIdentifier, Range, Url, Position, Location};
 use url_serde;
 
@@ -149,7 +149,7 @@ pub struct Runnable {
     pub label: String,
     pub bin: String,
     pub args: Vec<String>,
-    pub env: HashMap<String, String>,
+    pub env: FxHashMap<String, String>,
 }
 
 #[derive(Serialize, Debug)]
diff --git a/crates/ra_lsp_server/src/server_world.rs b/crates/ra_lsp_server/src/server_world.rs
index 865f7c491..c4cdf83d4 100644
--- a/crates/ra_lsp_server/src/server_world.rs
+++ b/crates/ra_lsp_server/src/server_world.rs
@@ -1,10 +1,10 @@
 use std::{
     fs,
     path::{PathBuf, Path},
-    collections::HashMap,
     sync::Arc,
 };
 
+use rustc_hash::FxHashMap;
 use languageserver_types::Url;
 use ra_analysis::{FileId, AnalysisHost, Analysis, CrateGraph, CrateId, LibraryData, FileResolver};
 
@@ -20,7 +20,7 @@ pub struct ServerWorldState {
     pub workspaces: Arc<Vec<CargoWorkspace>>,
     pub analysis_host: AnalysisHost,
     pub path_map: PathMap,
-    pub mem_map: HashMap<FileId, Option<String>>,
+    pub mem_map: FxHashMap<FileId, Option<String>>,
 }
 
 #[derive(Clone)]
@@ -36,7 +36,7 @@ impl ServerWorldState {
             workspaces: Arc::new(Vec::new()),
             analysis_host: AnalysisHost::new(),
             path_map: PathMap::new(),
-            mem_map: HashMap::new(),
+            mem_map: FxHashMap::default(),
         }
     }
     pub fn apply_fs_changes(&mut self, events: Vec<FileEvent>) {
@@ -121,7 +121,7 @@ impl ServerWorldState {
         Ok(file_id)
     }
     pub fn set_workspaces(&mut self, ws: Vec<CargoWorkspace>) {
-        let mut crate_roots = HashMap::new();
+        let mut crate_roots = FxHashMap::default();
         ws.iter()
           .flat_map(|ws| {
               ws.packages()
diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index f27093291..ef7b5b1a1 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -231,6 +231,24 @@ impl<'a> AstNode<'a> for CastExpr<'a> {
 
 impl<'a> CastExpr<'a> {}
 
+// Comment
+#[derive(Debug, Clone, Copy)]
+pub struct Comment<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for Comment<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            COMMENT => Some(Comment { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> Comment<'a> {}
+
 // Condition
 #[derive(Debug, Clone, Copy)]
 pub struct Condition<'a> {
diff --git a/crates/ra_syntax/src/ast/mod.rs b/crates/ra_syntax/src/ast/mod.rs
index c1570b868..10dac72e5 100644
--- a/crates/ra_syntax/src/ast/mod.rs
+++ b/crates/ra_syntax/src/ast/mod.rs
@@ -99,6 +99,49 @@ impl<'a> Lifetime<'a> {
     }
 }
 
+impl<'a> Comment<'a> {
+    pub fn text(&self) -> SmolStr {
+        self.syntax().leaf_text().unwrap().clone()
+    }
+
+    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 prefix(&self) -> &'static str {
+        self.flavor().prefix()
+    }
+}
+
+#[derive(Debug)]
+pub enum CommentFlavor {
+    Line,
+    Doc,
+    ModuleDoc,
+    Multiline
+}
+
+impl CommentFlavor {
+    pub fn prefix(&self) -> &'static str {
+        use self::CommentFlavor::*;
+        match *self {
+            Line => "//",
+            Doc => "///",
+            ModuleDoc => "//!",
+            Multiline => "/*"
+        }
+    }
+}
+
 impl<'a> Name<'a> {
     pub fn text(&self) -> SmolStr {
         let ident = self.syntax().first_child()
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index 4b990fd8d..9da0c2c13 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -537,5 +537,6 @@ Grammar(
         "PathSegment": (
             options: [ "NameRef" ]
         ),
+        "Comment": (),
     },
 )