Fix syntax highlighting of recursive macros

Add syntax highlighting for the BANG (`!`) token if the parent is `MACRO_CALL`.

crates/ra_ide/src/snapshots/highlighting.html

@@ -62,6 +62,12 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
     }
 }
 
+<span class="macro">macro_rules!</span> <span class="macro declaration">noop</span> {
+    ($expr:expr) =&gt; {
+        $expr
+    }
+}
+
 <span class="comment">// comment</span>
 <span class="keyword">fn</span> <span class="function declaration">main</span>() {
     <span class="macro">println!</span>(<span class="string_literal">"Hello, {}!"</span>, <span class="numeric_literal">92</span>);
@@ -80,6 +86,8 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
         <span class="comment">// Do nothing</span>
     }
 
+    <span class="macro">noop!</span>(<span class="macro">noop</span><span class="macro">!</span>(<span class="numeric_literal">1</span>));
+
     <span class="keyword">let</span> <span class="keyword">mut</span> <span class="variable declaration mutable">x</span> = <span class="numeric_literal">42</span>;
     <span class="keyword">let</span> <span class="variable declaration mutable">y</span> = &<span class="keyword">mut</span> <span class="variable mutable">x</span>;
     <span class="keyword">let</span> <span class="variable declaration">z</span> = &<span class="variable mutable">y</span>;

crates/ra_ide/src/syntax_highlighting.rs

@@ -160,9 +160,12 @@ pub(crate) fn highlight(
             // Check if macro takes a format string and remember it for highlighting later.
             // The macros that accept a format string expand to a compiler builtin macros
             // `format_args` and `format_args_nl`.
-            if let Some(fmt_macro_call) = parent.parent().and_then(ast::MacroCall::cast) {
+            if let Some(name) = parent
-                if let Some(name) =
+                .parent()
-                    fmt_macro_call.path().and_then(|p| p.segment()).and_then(|s| s.name_ref())
+                .and_then(ast::MacroCall::cast)
+                .and_then(|mc| mc.path())
+                .and_then(|p| p.segment())
+                .and_then(|s| s.name_ref())
             {
                 match name.text().as_str() {
                     "format_args" | "format_args_nl" => {
@@ -178,7 +181,6 @@ pub(crate) fn highlight(
                     _ => {}
                 }
             }
-            }
 
             // We only care Name and Name_ref
             match (token.kind(), parent.kind()) {
@@ -493,6 +495,9 @@ fn highlight_element(
             h |= HighlightModifier::Unsafe;
             h
         }
+        T![!] if element.parent().and_then(ast::MacroCall::cast).is_some() => {
+            Highlight::new(HighlightTag::Macro)
+        }
 
         k if k.is_keyword() => {
             let h = Highlight::new(HighlightTag::Keyword);

crates/ra_ide/src/syntax_highlighting/tests.rs

@@ -43,6 +43,12 @@ def_fn! {
     }
 }
 
+macro_rules! noop {
+    ($expr:expr) => {
+        $expr
+    }
+}
+
 // comment
 fn main() {
     println!("Hello, {}!", 92);
@@ -61,6 +67,8 @@ fn main() {
         // Do nothing
     }
 
+    noop!(noop!(1));
+
     let mut x = 42;
     let y = &mut x;
     let z = &y;