5 files changed, 45 insertions, 1 deletions

diff --git a/crates/ide/src/diagnostics.rs b/crates/ide/src/diagnostics.rs
index 90574cb35..232074c3d 100644
--- a/crates/ide/src/diagnostics.rs
+++ b/crates/ide/src/diagnostics.rs
@@ -613,7 +613,7 @@ fn main() {
 pub struct Foo { pub a: i32, pub b: i32 }
 "#,
             r#"
-fn {a:42, b: ()} {}
+fn some(, b: ()} {}
 fn items() {}
 fn here() {}
 
diff --git a/crates/ide/src/syntax_highlighting.rs b/crates/ide/src/syntax_highlighting.rs
index b35c03162..750848467 100644
--- a/crates/ide/src/syntax_highlighting.rs
+++ b/crates/ide/src/syntax_highlighting.rs
@@ -763,6 +763,9 @@ fn highlight_def(db: &RootDatabase, def: Definition) -> Highlight {
             if local.is_mut(db) || local.ty(db).is_mutable_reference() {
                 h |= HighlightModifier::Mutable;
             }
+            if local.ty(db).as_callable(db).is_some() || local.ty(db).impls_fnonce(db) {
+                h |= HighlightModifier::Callable;
+            }
             return h;
         }
     }
diff --git a/crates/ide/src/syntax_highlighting/tags.rs b/crates/ide/src/syntax_highlighting/tags.rs
index c1b817f06..e8f78ad52 100644
--- a/crates/ide/src/syntax_highlighting/tags.rs
+++ b/crates/ide/src/syntax_highlighting/tags.rs
@@ -64,6 +64,7 @@ pub enum HighlightModifier {
     Mutable,
     Consuming,
     Unsafe,
+    Callable,
 }
 
 impl HighlightTag {
@@ -122,6 +123,7 @@ impl HighlightModifier {
         HighlightModifier::Mutable,
         HighlightModifier::Consuming,
         HighlightModifier::Unsafe,
+        HighlightModifier::Callable,
     ];
 
     fn as_str(self) -> &'static str {
@@ -134,6 +136,7 @@ impl HighlightModifier {
             HighlightModifier::Mutable => "mutable",
             HighlightModifier::Consuming => "consuming",
             HighlightModifier::Unsafe => "unsafe",
+            HighlightModifier::Callable => "callable",
         }
     }
 
diff --git a/crates/ide/src/syntax_highlighting/test_data/highlighting.html b/crates/ide/src/syntax_highlighting/test_data/highlighting.html
index 0bb0928e4..0cb84866d 100644
--- a/crates/ide/src/syntax_highlighting/test_data/highlighting.html
+++ b/crates/ide/src/syntax_highlighting/test_data/highlighting.html
@@ -44,6 +44,17 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
     <span class="keyword">pub</span> <span class="keyword">trait</span> <span class="trait declaration">Copy</span> <span class="punctuation">{</span><span class="punctuation">}</span>
 <span class="punctuation">}</span>
 
+<span class="keyword">pub</span> <span class="keyword">mod</span> <span class="module declaration">ops</span> <span class="punctuation">{</span>
+    <span class="attribute">#</span><span class="attribute">[</span><span class="function attribute">lang</span><span class="attribute"> </span><span class="operator">=</span><span class="attribute"> </span><span class="string_literal">"fn_once"</span><span class="attribute">]</span>
+    <span class="keyword">pub</span> <span class="keyword">trait</span> <span class="trait declaration">FnOnce</span><span class="punctuation">&lt;</span><span class="type_param declaration">Args</span><span class="punctuation">&gt;</span> <span class="punctuation">{</span><span class="punctuation">}</span>
+
+    <span class="attribute">#</span><span class="attribute">[</span><span class="function attribute">lang</span><span class="attribute"> </span><span class="operator">=</span><span class="attribute"> </span><span class="string_literal">"fn_mut"</span><span class="attribute">]</span>
+    <span class="keyword">pub</span> <span class="keyword">trait</span> <span class="trait declaration">FnMut</span><span class="punctuation">&lt;</span><span class="type_param declaration">Args</span><span class="punctuation">&gt;</span><span class="punctuation">:</span> <span class="trait">FnOnce</span><span class="punctuation">&lt;</span><span class="type_param">Args</span><span class="punctuation">&gt;</span> <span class="punctuation">{</span><span class="punctuation">}</span>
+
+    <span class="attribute">#</span><span class="attribute">[</span><span class="function attribute">lang</span><span class="attribute"> </span><span class="operator">=</span><span class="attribute"> </span><span class="string_literal">"fn"</span><span class="attribute">]</span>
+    <span class="keyword">pub</span> <span class="keyword">trait</span> <span class="trait declaration">Fn</span><span class="punctuation">&lt;</span><span class="type_param declaration">Args</span><span class="punctuation">&gt;</span><span class="punctuation">:</span> <span class="trait">FnMut</span><span class="punctuation">&lt;</span><span class="type_param">Args</span><span class="punctuation">&gt;</span> <span class="punctuation">{</span><span class="punctuation">}</span>
+<span class="punctuation">}</span>
+
 
 <span class="keyword">struct</span> <span class="struct declaration">Foo</span> <span class="punctuation">{</span>
     <span class="keyword">pub</span> <span class="field declaration">x</span><span class="punctuation">:</span> <span class="builtin_type">i32</span><span class="punctuation">,</span>
@@ -99,6 +110,11 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
     <span class="function">foo</span><span class="operator">::</span><span class="punctuation">&lt;</span><span class="lifetime">'a</span><span class="punctuation">,</span> <span class="builtin_type">i32</span><span class="punctuation">&gt;</span><span class="punctuation">(</span><span class="punctuation">)</span>
 <span class="punctuation">}</span>
 
+<span class="keyword">use</span> <span class="module">ops</span><span class="operator">::</span><span class="trait">Fn</span><span class="punctuation">;</span>
+<span class="keyword">fn</span> <span class="function declaration">baz</span><span class="punctuation">&lt;</span><span class="type_param declaration">F</span><span class="punctuation">:</span> <span class="trait">Fn</span><span class="punctuation">(</span><span class="punctuation">)</span> <span class="operator">-&gt;</span> <span class="punctuation">(</span><span class="punctuation">)</span><span class="punctuation">&gt;</span><span class="punctuation">(</span><span class="value_param declaration callable">f</span><span class="punctuation">:</span> <span class="type_param">F</span><span class="punctuation">)</span> <span class="punctuation">{</span>
+    <span class="value_param callable">f</span><span class="punctuation">(</span><span class="punctuation">)</span>
+<span class="punctuation">}</span>
+
 <span class="macro">macro_rules!</span> <span class="macro declaration">def_fn</span> <span class="punctuation">{</span>
     <span class="punctuation">(</span><span class="punctuation">$</span><span class="punctuation">(</span><span class="punctuation">$</span>tt<span class="punctuation">:</span>tt<span class="punctuation">)</span><span class="punctuation">*</span><span class="punctuation">)</span> <span class="operator">=</span><span class="punctuation">&gt;</span> <span class="punctuation">{</span><span class="punctuation">$</span><span class="punctuation">(</span><span class="punctuation">$</span>tt<span class="punctuation">)</span><span class="punctuation">*</span><span class="punctuation">}</span>
 <span class="punctuation">}</span>
@@ -157,6 +173,9 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
     <span class="variable mutable">copy</span><span class="punctuation">.</span><span class="function">quop</span><span class="punctuation">(</span><span class="punctuation">)</span><span class="punctuation">;</span>
     <span class="variable mutable">copy</span><span class="punctuation">.</span><span class="function mutable">qux</span><span class="punctuation">(</span><span class="punctuation">)</span><span class="punctuation">;</span>
     <span class="variable mutable">copy</span><span class="punctuation">.</span><span class="function">baz</span><span class="punctuation">(</span><span class="variable mutable">copy</span><span class="punctuation">)</span><span class="punctuation">;</span>
+
+    <span class="keyword">let</span> <span class="variable declaration callable">a</span> <span class="operator">=</span> <span class="punctuation">|</span><span class="value_param declaration">x</span><span class="punctuation">|</span> <span class="value_param">x</span><span class="punctuation">;</span>
+    <span class="keyword">let</span> <span class="variable declaration callable">bar</span> <span class="operator">=</span> <span class="struct">Foo</span><span class="operator">::</span><span class="function">baz</span><span class="punctuation">;</span>
 <span class="punctuation">}</span>
 
 <span class="keyword">enum</span> <span class="enum declaration">Option</span><span class="punctuation">&lt;</span><span class="type_param declaration">T</span><span class="punctuation">&gt;</span> <span class="punctuation">{</span>
diff --git a/crates/ide/src/syntax_highlighting/tests.rs b/crates/ide/src/syntax_highlighting/tests.rs
index 126363b8b..da20c300e 100644
--- a/crates/ide/src/syntax_highlighting/tests.rs
+++ b/crates/ide/src/syntax_highlighting/tests.rs
@@ -18,6 +18,17 @@ pub mod marker {
     pub trait Copy {}
 }
 
+pub mod ops {
+    #[lang = "fn_once"]
+    pub trait FnOnce<Args> {}
+
+    #[lang = "fn_mut"]
+    pub trait FnMut<Args>: FnOnce<Args> {}
+
+    #[lang = "fn"]
+    pub trait Fn<Args>: FnMut<Args> {}
+}
+
 
 struct Foo {
     pub x: i32,
@@ -73,6 +84,11 @@ fn foo<'a, T>() -> T {
     foo::<'a, i32>()
 }
 
+use ops::Fn;
+fn baz<F: Fn() -> ()>(f: F) {
+    f()
+}
+
 macro_rules! def_fn {
     ($($tt:tt)*) => {$($tt)*}
 }
@@ -131,6 +147,9 @@ fn main() {
     copy.quop();
     copy.qux();
     copy.baz(copy);
+
+    let a = |x| x;
+    let bar = Foo::baz;
 }
 
 enum Option<T> {