3 files changed, 63 insertions, 3 deletions

diff --git a/editors/code/package.json b/editors/code/package.json
index 9f98ab736..946145df8 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -401,6 +401,21 @@
                 ]
             }
         ],
+        "languages": [
+            {
+                "id": "ra_syntax_tree",
+                "extensions": [
+                    ".rast"
+                ]
+            }
+        ],
+        "grammars": [
+            {
+                "language": "ra_syntax_tree",
+                "scopeName": "source.ra_syntax_tree",
+                "path": "ra_syntax_tree.tmGrammar.json"
+            }
+        ],
         "problemMatchers": [
             {
                 "name": "rustc",
@@ -440,6 +455,15 @@
                     "light": "#747474",
                     "highContrast": "#BEBEBE"
                 }
+            },
+            {
+                "id": "rust_analyzer.syntaxTreeBorder",
+                "description": "Color of the border displayed in the Rust source code for the selected syntax node (see \"Show Syntax Tree\" command)",
+                "defaults": {
+                    "dark": "#ffffff",
+                    "light": "#b700ff",
+                    "highContrast": "#b700ff"
+                }
             }
         ],
         "semanticTokenTypes": [
diff --git a/editors/code/ra_syntax_tree.tmGrammar.json b/editors/code/ra_syntax_tree.tmGrammar.json
new file mode 100644
index 000000000..0d72a3e36
--- /dev/null
+++ b/editors/code/ra_syntax_tree.tmGrammar.json
@@ -0,0 +1,31 @@
+{
+    "$schema": "https://raw.githubusercontent.com/martinring/tmlanguage/master/tmlanguage.json",
+
+    "scopeName": "source.ra_syntax_tree",
+    "patterns": [
+        { "include": "#node_type" },
+        { "include": "#node_range_index" },
+        { "include": "#token_text" }
+    ],
+    "repository": {
+        "node_type": {
+            "match": "^\\s*([A-Z_]+?)@",
+            "captures": {
+                "1": {
+                    "name": "entity.name.class"
+                }
+            }
+        },
+        "node_range_index": {
+            "match": "\\d+",
+            "name": "constant.numeric"
+        },
+        "token_text": {
+            "match": "\".+\"",
+            "name": "string"
+        }
+    },
+    "fileTypes": [
+        "rast"
+    ]
+}
diff --git a/editors/code/src/commands/syntax_tree.ts b/editors/code/src/commands/syntax_tree.ts
index 996c7a716..8d71cb39e 100644
--- a/editors/code/src/commands/syntax_tree.ts
+++ b/editors/code/src/commands/syntax_tree.ts
@@ -15,6 +15,9 @@ export function syntaxTree(ctx: Ctx): Cmd {
     void new AstInspector(ctx);
 
     ctx.pushCleanup(vscode.workspace.registerTextDocumentContentProvider(AST_FILE_SCHEME, tdcp));
+    ctx.pushCleanup(vscode.languages.setLanguageConfiguration("ra_syntax_tree", {
+        brackets: [["[", ")"]],
+    }));
 
     return async () => {
         const editor = vscode.window.activeTextEditor;
@@ -36,7 +39,7 @@ export function syntaxTree(ctx: Ctx): Cmd {
 }
 
 class TextDocumentContentProvider implements vscode.TextDocumentContentProvider {
-    readonly uri = vscode.Uri.parse('rust-analyzer://syntaxtree');
+    readonly uri = vscode.Uri.parse('rust-analyzer://syntaxtree/tree.rast');
     readonly eventEmitter = new vscode.EventEmitter<vscode.Uri>();
 
 
@@ -81,8 +84,10 @@ class TextDocumentContentProvider implements vscode.TextDocumentContentProvider
 // https://code.visualstudio.com/api/extension-guides/tree-view
 class AstInspector implements vscode.HoverProvider, Disposable {
     private static readonly astDecorationType = vscode.window.createTextEditorDecorationType({
-        fontStyle: "normal",
-        border: "#ffffff 1px solid",
+        borderColor: new vscode.ThemeColor('rust_analyzer.syntaxTreeBorder'),
+        borderStyle: "solid",
+        borderWidth: "2px",
+
     });
     private rustEditor: undefined | RustEditor;