Merge #1544

1544: Highlight mutable variables differently r=matklad a=viorina

![Screenshot from 2019-07-18 19-04-57](https://user-images.githubusercontent.com/6714973/61473539-3f5d3000-a98f-11e9-99ec-a4115b2ba66b.png)


Co-authored-by: Ekaterina Babshukova <[email protected]>

3 files changed, 102 insertions, 54 deletions

diff --git a/crates/ra_ide_api/src/snapshots/highlighting.html b/crates/ra_ide_api/src/snapshots/highlighting.html
index d79d35bf3..709816d0d 100644
--- a/crates/ra_ide_api/src/snapshots/highlighting.html
+++ b/crates/ra_ide_api/src/snapshots/highlighting.html
@@ -1,21 +1,22 @@
 
 <style>
-body       { margin: 0; }
-pre        { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4em; }
-
-.comment   { color: #7F9F7F; }
-.string    { color: #CC9393; }
-.function  { color: #93E0E3; }
-.parameter { color: #94BFF3; }
-.builtin   { color: #DD6718; }
-.text      { color: #DCDCCC; }
-.attribute { color: #BFEBBF; }
-.literal   { color: #DFAF8F; }
-.macro     { color: #DFAF8F; }
-
-.keyword           { color: #F0DFAF; }
-.keyword\.unsafe  { color: #F0DFAF; font-weight: bold; }
-.keyword\.control { color: #DC8CC3; }
+body                { margin: 0; }
+pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4em; }
+
+.comment            { color: #7F9F7F; }
+.string             { color: #CC9393; }
+.function           { color: #93E0E3; }
+.parameter          { color: #94BFF3; }
+.builtin            { color: #DD6718; }
+.text               { color: #DCDCCC; }
+.attribute          { color: #BFEBBF; }
+.literal            { color: #DFAF8F; }
+.macro              { color: #DFAF8F; }
+.variable\.mut     { color: #DFAF8F; }
+
+.keyword            { color: #F0DFAF; }
+.keyword\.unsafe   { color: #F0DFAF; font-weight: bold; }
+.keyword\.control  { color: #DC8CC3; }
 </style>
 <pre><code><span class="attribute">#</span><span class="attribute">[</span><span class="attribute">derive</span><span class="attribute">(</span><span class="attribute">Clone</span><span class="attribute">,</span><span class="attribute"> </span><span class="attribute">Debug</span><span class="attribute">)</span><span class="attribute">]</span>
 <span class="keyword">struct</span> <span class="type">Foo</span> {
@@ -32,9 +33,15 @@ pre        { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4e
 <span class="keyword">fn</span> <span class="function">main</span>() {
     <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Hello, {}!"</span>, <span class="literal">92</span>);
 
-    <span class="keyword">let</span> <span class="keyword">mut</span> <span class="variable" data-binding-hash="9636295041291189729" style="color: hsl(51,57%,74%);">vec</span> = <span class="text">Vec</span>::<span class="text">new</span>();
+    <span class="keyword">let</span> <span class="keyword">mut</span> <span class="variable.mut">vec</span> = <span class="text">Vec</span>::<span class="text">new</span>();
     <span class="keyword.control">if</span> <span class="keyword">true</span> {
-        <span class="variable" data-binding-hash="8496027264380925433" style="color: hsl(18,48%,55%);">vec</span>.<span class="text">push</span>(<span class="type">Foo</span> { <span class="field">x</span>: <span class="literal">0</span>, <span class="field">y</span>: <span class="literal">1</span> });
+        <span class="variable.mut">vec</span>.<span class="text">push</span>(<span class="type">Foo</span> { <span class="field">x</span>: <span class="literal">0</span>, <span class="field">y</span>: <span class="literal">1</span> });
     }
-    <span class="keyword.unsafe">unsafe</span> { <span class="variable" data-binding-hash="8496027264380925433" style="color: hsl(18,48%,55%);">vec</span>.<span class="text">set_len</span>(<span class="literal">0</span>); }
+    <span class="keyword.unsafe">unsafe</span> { <span class="variable.mut">vec</span>.<span class="text">set_len</span>(<span class="literal">0</span>); }
+
+    <span class="keyword">let</span> <span class="keyword">mut</span> <span class="variable.mut">x</span> = <span class="literal">42</span>;
+    <span class="keyword">let</span> <span class="variable.mut">y</span> = &<span class="keyword">mut</span> <span class="variable.mut">x</span>;
+    <span class="keyword">let</span> <span class="variable">z</span> = &<span class="variable.mut">y</span>;
+
+    <span class="variable.mut">y</span>;
 }</code></pre>
\ No newline at end of file
diff --git a/crates/ra_ide_api/src/snapshots/rainbow_highlighting.html b/crates/ra_ide_api/src/snapshots/rainbow_highlighting.html
index 729d129d0..ad3935b5d 100644
--- a/crates/ra_ide_api/src/snapshots/rainbow_highlighting.html
+++ b/crates/ra_ide_api/src/snapshots/rainbow_highlighting.html
@@ -1,21 +1,22 @@
 
 <style>
-body       { margin: 0; }
-pre        { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4em; }
+body                { margin: 0; }
+pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4em; }
 
-.comment   { color: #7F9F7F; }
-.string    { color: #CC9393; }
-.function  { color: #93E0E3; }
-.parameter { color: #94BFF3; }
-.builtin   { color: #DD6718; }
-.text      { color: #DCDCCC; }
-.attribute { color: #BFEBBF; }
-.literal   { color: #DFAF8F; }
-.macro     { color: #DFAF8F; }
+.comment            { color: #7F9F7F; }
+.string             { color: #CC9393; }
+.function           { color: #93E0E3; }
+.parameter          { color: #94BFF3; }
+.builtin            { color: #DD6718; }
+.text               { color: #DCDCCC; }
+.attribute          { color: #BFEBBF; }
+.literal            { color: #DFAF8F; }
+.macro              { color: #DFAF8F; }
+.variable\.mut     { color: #DFAF8F; }
 
-.keyword           { color: #F0DFAF; }
-.keyword\.unsafe  { color: #F0DFAF; font-weight: bold; }
-.keyword\.control { color: #DC8CC3; }
+.keyword            { color: #F0DFAF; }
+.keyword\.unsafe   { color: #F0DFAF; font-weight: bold; }
+.keyword\.control  { color: #DC8CC3; }
 </style>
 <pre><code><span class="keyword">fn</span> <span class="function">main</span>() {
     <span class="keyword">let</span> <span class="variable" data-binding-hash="3888301305669440875" style="color: hsl(242,59%,59%);">hello</span> = <span class="string">"hello"</span>;
diff --git a/crates/ra_ide_api/src/syntax_highlighting.rs b/crates/ra_ide_api/src/syntax_highlighting.rs
index d70ceb7d1..d84ae2cb2 100644
--- a/crates/ra_ide_api/src/syntax_highlighting.rs
+++ b/crates/ra_ide_api/src/syntax_highlighting.rs
@@ -1,9 +1,11 @@
 use rustc_hash::{FxHashMap, FxHashSet};
 
+use hir::{Mutability, Ty};
 use ra_db::SourceDatabase;
 use ra_prof::profile;
 use ra_syntax::{
-    ast, AstNode, Direction, SmolStr, SyntaxElement, SyntaxKind, SyntaxKind::*, TextRange, T,
+    ast, AstNode, Direction, Pat, PatKind, SmolStr, SyntaxElement, SyntaxKind, SyntaxKind::*,
+    TextRange, T,
 };
 
 use crate::{db::RootDatabase, FileId};
@@ -30,6 +32,27 @@ fn is_control_keyword(kind: SyntaxKind) -> bool {
     }
 }
 
+fn is_variable_mutable(db: &RootDatabase, analyzer: &hir::SourceAnalyzer, pat: &Pat) -> bool {
+    let ty = analyzer.type_of_pat(db, pat).unwrap_or(Ty::Unknown);
+    let is_ty_mut = {
+        if let Some((_, mutability)) = ty.as_reference() {
+            match mutability {
+                Mutability::Shared => false,
+                Mutability::Mut => true,
+            }
+        } else {
+            false
+        }
+    };
+
+    let is_pat_mut = match pat.kind() {
+        PatKind::BindPat(bind_pat) => bind_pat.is_mutable(),
+        _ => false,
+    };
+
+    is_ty_mut || is_pat_mut
+}
+
 pub(crate) fn highlight(db: &RootDatabase, file_id: FileId) -> Vec<HighlightedRange> {
     let _p = profile("highlight");
     let parse = db.parse(file_id);
@@ -97,7 +120,11 @@ pub(crate) fn highlight(db: &RootDatabase, file_id: FileId) -> Vec<HighlightedRa
                                 calc_binding_hash(file_id, &text, *shadow_count)
                             });
 
-                            "variable"
+                            if is_variable_mutable(db, &analyzer, ptr.to_node(root)) {
+                                "variable.mut"
+                            } else {
+                                "variable"
+                            }
                         }
                         Some(SelfParam(_)) => "type",
                         Some(GenericParam(_)) => "type",
@@ -109,7 +136,8 @@ pub(crate) fn highlight(db: &RootDatabase, file_id: FileId) -> Vec<HighlightedRa
             }
             NAME => {
                 if let Some(name) = node.as_node().and_then(ast::Name::cast) {
-                    if name.syntax().ancestors().any(|x| ast::BindPat::cast(x).is_some()) {
+                    let analyzer = hir::SourceAnalyzer::new(db, file_id, name.syntax(), None);
+                    if let Some(pat) = name.syntax().ancestors().find_map(Pat::cast) {
                         binding_hash = Some({
                             let text = name.syntax().text().to_smol_string();
                             let shadow_count =
@@ -117,7 +145,12 @@ pub(crate) fn highlight(db: &RootDatabase, file_id: FileId) -> Vec<HighlightedRa
                             *shadow_count += 1;
                             calc_binding_hash(file_id, &text, *shadow_count)
                         });
-                        "variable"
+
+                        if is_variable_mutable(db, &analyzer, pat) {
+                            "variable.mut"
+                        } else {
+                            "variable"
+                        }
                     } else if name
                         .syntax()
                         .parent()
@@ -241,22 +274,23 @@ fn html_escape(text: &str) -> String {
 
 const STYLE: &str = "
 <style>
-body       { margin: 0; }
-pre        { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4em; }
-
-.comment   { color: #7F9F7F; }
-.string    { color: #CC9393; }
-.function  { color: #93E0E3; }
-.parameter { color: #94BFF3; }
-.builtin   { color: #DD6718; }
-.text      { color: #DCDCCC; }
-.attribute { color: #BFEBBF; }
-.literal   { color: #DFAF8F; }
-.macro     { color: #DFAF8F; }
-
-.keyword           { color: #F0DFAF; }
-.keyword\\.unsafe  { color: #F0DFAF; font-weight: bold; }
-.keyword\\.control { color: #DC8CC3; }
+body                { margin: 0; }
+pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4em; }
+
+.comment            { color: #7F9F7F; }
+.string             { color: #CC9393; }
+.function           { color: #93E0E3; }
+.parameter          { color: #94BFF3; }
+.builtin            { color: #DD6718; }
+.text               { color: #DCDCCC; }
+.attribute          { color: #BFEBBF; }
+.literal            { color: #DFAF8F; }
+.macro              { color: #DFAF8F; }
+.variable\\.mut     { color: #DFAF8F; }
+
+.keyword            { color: #F0DFAF; }
+.keyword\\.unsafe   { color: #F0DFAF; font-weight: bold; }
+.keyword\\.control  { color: #DC8CC3; }
 </style>
 ";
 
@@ -289,12 +323,18 @@ fn main() {
         vec.push(Foo { x: 0, y: 1 });
     }
     unsafe { vec.set_len(0); }
+
+    let mut x = 42;
+    let y = &mut x;
+    let z = &y;
+
+    y;
 }
 "#
             .trim(),
         );
         let dst_file = project_dir().join("crates/ra_ide_api/src/snapshots/highlighting.html");
-        let actual_html = &analysis.highlight_as_html(file_id, true).unwrap();
+        let actual_html = &analysis.highlight_as_html(file_id, false).unwrap();
         let expected_html = &read_text(&dst_file);
         std::fs::write(dst_file, &actual_html).unwrap();
         assert_eq_text!(expected_html, actual_html);