10 files changed, 143 insertions, 71 deletions

diff --git a/crates/ra_ide/src/completion/complete_unqualified_path.rs b/crates/ra_ide/src/completion/complete_unqualified_path.rs
index 56cd086c6..f559f2b97 100644
--- a/crates/ra_ide/src/completion/complete_unqualified_path.rs
+++ b/crates/ra_ide/src/completion/complete_unqualified_path.rs
@@ -4,7 +4,7 @@ use hir::ScopeDef;
 use test_utils::tested_by;
 
 use crate::completion::{CompletionContext, Completions};
-use hir::{Adt, ModuleDef};
+use hir::{Adt, ModuleDef, Type};
 use ra_syntax::AstNode;
 
 pub(super) fn complete_unqualified_path(acc: &mut Completions, ctx: &CompletionContext) {
@@ -15,7 +15,9 @@ pub(super) fn complete_unqualified_path(acc: &mut Completions, ctx: &CompletionC
         return;
     }
 
-    complete_enum_variants(acc, ctx);
+    if let Some(ty) = &ctx.expected_type {
+        complete_enum_variants(acc, ctx, ty);
+    }
 
     if ctx.is_pat_binding_or_const {
         return;
@@ -34,26 +36,24 @@ pub(super) fn complete_unqualified_path(acc: &mut Completions, ctx: &CompletionC
     });
 }
 
-fn complete_enum_variants(acc: &mut Completions, ctx: &CompletionContext) {
-    if let Some(ty) = ctx.expected_type_of(&ctx.token.parent()) {
-        if let Some(Adt::Enum(enum_data)) = ty.as_adt() {
-            let variants = enum_data.variants(ctx.db);
-
-            let module = if let Some(module) = ctx.scope().module() {
-                // Compute path from the completion site if available.
-                module
-            } else {
-                // Otherwise fall back to the enum's definition site.
-                enum_data.module(ctx.db)
-            };
-
-            for variant in variants {
-                if let Some(path) = module.find_use_path(ctx.db, ModuleDef::from(variant)) {
-                    // Variants with trivial paths are already added by the existing completion logic,
-                    // so we should avoid adding these twice
-                    if path.segments.len() > 1 {
-                        acc.add_enum_variant(ctx, variant, Some(path.to_string()));
-                    }
+fn complete_enum_variants(acc: &mut Completions, ctx: &CompletionContext, ty: &Type) {
+    if let Some(Adt::Enum(enum_data)) = ty.as_adt() {
+        let variants = enum_data.variants(ctx.db);
+
+        let module = if let Some(module) = ctx.scope().module() {
+            // Compute path from the completion site if available.
+            module
+        } else {
+            // Otherwise fall back to the enum's definition site.
+            enum_data.module(ctx.db)
+        };
+
+        for variant in variants {
+            if let Some(path) = module.find_use_path(ctx.db, ModuleDef::from(variant)) {
+                // Variants with trivial paths are already added by the existing completion logic,
+                // so we should avoid adding these twice
+                if path.segments.len() > 1 {
+                    acc.add_enum_variant(ctx, variant, Some(path.to_string()));
                 }
             }
         }
diff --git a/crates/ra_ide/src/completion/completion_context.rs b/crates/ra_ide/src/completion/completion_context.rs
index 5f2797e41..118fceb2e 100644
--- a/crates/ra_ide/src/completion/completion_context.rs
+++ b/crates/ra_ide/src/completion/completion_context.rs
@@ -5,7 +5,7 @@ use ra_db::SourceDatabase;
 use ra_ide_db::RootDatabase;
 use ra_syntax::{
     algo::{find_covering_element, find_node_at_offset},
-    ast, AstNode,
+    ast, match_ast, AstNode,
     SyntaxKind::*,
     SyntaxNode, SyntaxToken, TextRange, TextSize,
 };
@@ -26,6 +26,7 @@ pub(crate) struct CompletionContext<'a> {
     /// The token before the cursor, in the macro-expanded file.
     pub(super) token: SyntaxToken,
     pub(super) krate: Option<hir::Crate>,
+    pub(super) expected_type: Option<Type>,
     pub(super) name_ref_syntax: Option<ast::NameRef>,
     pub(super) function_syntax: Option<ast::FnDef>,
     pub(super) use_item_syntax: Option<ast::UseItem>,
@@ -93,6 +94,7 @@ impl<'a> CompletionContext<'a> {
             token,
             offset: position.offset,
             krate,
+            expected_type: None,
             name_ref_syntax: None,
             function_syntax: None,
             use_item_syntax: None,
@@ -175,23 +177,30 @@ impl<'a> CompletionContext<'a> {
         self.sema.scope_at_offset(&self.token.parent(), self.offset)
     }
 
-    pub(crate) fn expected_type_of(&self, node: &SyntaxNode) -> Option<Type> {
-        for ancestor in node.ancestors() {
-            if let Some(pat) = ast::Pat::cast(ancestor.clone()) {
-                return self.sema.type_of_pat(&pat);
-            } else if let Some(expr) = ast::Expr::cast(ancestor) {
-                return self.sema.type_of_expr(&expr);
-            }
-        }
-        None
-    }
-
     fn fill(
         &mut self,
         original_file: &SyntaxNode,
         file_with_fake_ident: SyntaxNode,
         offset: TextSize,
     ) {
+        // FIXME: this is wrong in at least two cases:
+        //  * when there's no token `foo(<|>)`
+        //  * when there is a token, but it happens to have type of it's own
+        self.expected_type = self
+            .token
+            .ancestors()
+            .find_map(|node| {
+                let ty = match_ast! {
+                    match node {
+                        ast::Pat(it) => self.sema.type_of_pat(&it),
+                        ast::Expr(it) => self.sema.type_of_expr(&it),
+                        _ => return None,
+                    }
+                };
+                Some(ty)
+            })
+            .flatten();
+
         // First, let's try to complete a reference to some declaration.
         if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(&file_with_fake_ident, offset) {
             // Special case, `trait T { fn foo(i_am_a_name_ref) {} }`.
diff --git a/crates/ra_ide/src/completion/presentation.rs b/crates/ra_ide/src/completion/presentation.rs
index 7633cd7fd..77d354376 100644
--- a/crates/ra_ide/src/completion/presentation.rs
+++ b/crates/ra_ide/src/completion/presentation.rs
@@ -349,6 +349,14 @@ impl Builder {
         if ctx.use_item_syntax.is_some() || ctx.is_call {
             return self;
         }
+
+        // Don't add parentheses if the expected type is some function reference.
+        if let Some(ty) = &ctx.expected_type {
+            if ty.is_fn() {
+                return self;
+            }
+        }
+
         let cap = match ctx.config.snippet_cap {
             Some(it) => it,
             None => return self,
@@ -749,6 +757,54 @@ mod tests {
     }
 
     #[test]
+    fn no_call_parens_if_fn_ptr_needed() {
+        assert_debug_snapshot!(
+            do_reference_completion(
+                r"
+                fn somefn(with: u8, a: u8, lot: u8, of: u8, args: u8) {}
+
+                struct ManualVtable {
+                    method: fn(u8, u8, u8, u8, u8),
+                }
+
+                fn main() -> ManualVtable {
+                    ManualVtable {
+                        method: some<|>
+                    }
+                }
+                "
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "ManualVtable",
+                source_range: 295..299,
+                delete: 295..299,
+                insert: "ManualVtable",
+                kind: Struct,
+            },
+            CompletionItem {
+                label: "main",
+                source_range: 295..299,
+                delete: 295..299,
+                insert: "main",
+                kind: Function,
+                detail: "fn main() -> ManualVtable",
+            },
+            CompletionItem {
+                label: "somefn",
+                source_range: 295..299,
+                delete: 295..299,
+                insert: "somefn",
+                kind: Function,
+                detail: "fn somefn(with: u8, a: u8, lot: u8, of: u8, args: u8)",
+            },
+        ]
+        "###
+        );
+    }
+
+    #[test]
     fn arg_snippets_for_method_call() {
         assert_debug_snapshot!(
             do_reference_completion(
@@ -1179,7 +1235,7 @@ mod tests {
 
     #[test]
     fn test_struct_field_completion_in_record_lit() {
-        covers!(test_struct_field_completion_in_func_call);
+        covers!(test_struct_field_completion_in_record_lit);
         assert_debug_snapshot!(
         do_reference_completion(
                 r"
diff --git a/crates/ra_ide/src/snapshots/highlight_injection.html b/crates/ra_ide/src/snapshots/highlight_injection.html
index 6ec13bd80..ea026d7a0 100644
--- a/crates/ra_ide/src/snapshots/highlight_injection.html
+++ b/crates/ra_ide/src/snapshots/highlight_injection.html
@@ -20,6 +20,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .macro              { color: #94BFF3; }
 .module             { color: #AFD8AF; }
 .variable           { color: #DCDCCC; }
+.format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
diff --git a/crates/ra_ide/src/snapshots/highlight_strings.html b/crates/ra_ide/src/snapshots/highlight_strings.html
index 433f2e0c5..de06daf72 100644
--- a/crates/ra_ide/src/snapshots/highlight_strings.html
+++ b/crates/ra_ide/src/snapshots/highlight_strings.html
@@ -20,6 +20,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .macro              { color: #94BFF3; }
 .module             { color: #AFD8AF; }
 .variable           { color: #DCDCCC; }
+.format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
@@ -40,43 +41,43 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 <span class="keyword">fn</span> <span class="function declaration">main</span>() {
     <span class="comment">// from https://doc.rust-lang.org/std/fmt/index.html</span>
     <span class="macro">println!</span>(<span class="string_literal">"Hello"</span>);                 <span class="comment">// =&gt; "Hello"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"Hello, </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="string_literal">"world"</span>);   <span class="comment">// =&gt; "Hello, world!"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"The number is </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal">"</span>, <span class="numeric_literal">1</span>);   <span class="comment">// =&gt; "The number is 1"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="attribute">:</span><span class="attribute">?</span><span class="attribute">}</span><span class="string_literal">"</span>, (<span class="numeric_literal">3</span>, <span class="numeric_literal">4</span>));          <span class="comment">// =&gt; "(3, 4)"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="variable">value</span><span class="attribute">}</span><span class="string_literal">"</span>, value=<span class="numeric_literal">4</span>);      <span class="comment">// =&gt; "4"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal"> </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal">"</span>, <span class="numeric_literal">1</span>, <span class="numeric_literal">2</span>);           <span class="comment">// =&gt; "1 2"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="attribute">:</span><span class="numeric_literal">0</span><span class="numeric_literal">4</span><span class="attribute">}</span><span class="string_literal">"</span>, <span class="numeric_literal">42</span>);             <span class="comment">// =&gt; "0042" with leading zerosV</span>
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="numeric_literal">1</span><span class="attribute">}</span><span class="string_literal"> </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal"> </span><span class="attribute">{</span><span class="numeric_literal">0</span><span class="attribute">}</span><span class="string_literal"> </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal">"</span>, <span class="numeric_literal">1</span>, <span class="numeric_literal">2</span>);   <span class="comment">// =&gt; "2 1 1 2"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="variable">argument</span><span class="attribute">}</span><span class="string_literal">"</span>, argument = <span class="string_literal">"test"</span>);   <span class="comment">// =&gt; "test"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="variable">name</span><span class="attribute">}</span><span class="string_literal"> </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal">"</span>, <span class="numeric_literal">1</span>, name = <span class="numeric_literal">2</span>);          <span class="comment">// =&gt; "2 1"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="variable">a</span><span class="attribute">}</span><span class="string_literal"> </span><span class="attribute">{</span><span class="variable">c</span><span class="attribute">}</span><span class="string_literal"> </span><span class="attribute">{</span><span class="variable">b</span><span class="attribute">}</span><span class="string_literal">"</span>, a=<span class="string_literal">"a"</span>, b=<span class="char_literal">'b'</span>, c=<span class="numeric_literal">3</span>);  <span class="comment">// =&gt; "a 3 b"</span>
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="numeric_literal">5</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="numeric_literal">1</span><span class="attribute">$</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>, <span class="numeric_literal">5</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="numeric_literal">1</span><span class="attribute">:</span><span class="numeric_literal">0</span><span class="attribute">$</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="numeric_literal">5</span>, <span class="string_literal">"x"</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="variable">width</span><span class="attribute">$</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>, width = <span class="numeric_literal">5</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="attribute">&lt;</span><span class="numeric_literal">5</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="attribute">-</span><span class="attribute">&lt;</span><span class="numeric_literal">5</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="attribute">^</span><span class="numeric_literal">5</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="attribute">&gt;</span><span class="numeric_literal">5</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="attribute">+</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="numeric_literal">5</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="attribute">:</span><span class="attribute">#</span><span class="variable">x</span><span class="string_literal">}!"</span>, <span class="numeric_literal">27</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="numeric_literal">0</span><span class="numeric_literal">5</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="numeric_literal">5</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">:</span><span class="numeric_literal">0</span><span class="numeric_literal">5</span><span class="attribute">}</span><span class="string_literal">!"</span>, -<span class="numeric_literal">5</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="attribute">:</span><span class="attribute">#</span><span class="numeric_literal">0</span><span class="numeric_literal">10</span><span class="variable">x</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="numeric_literal">27</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="numeric_literal">0</span><span class="attribute">}</span><span class="string_literal"> is </span><span class="attribute">{</span><span class="numeric_literal">1</span><span class="attribute">:</span><span class="attribute">.</span><span class="numeric_literal">5</span><span class="attribute">}</span><span class="string_literal">"</span>, <span class="string_literal">"x"</span>, <span class="numeric_literal">0.01</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="numeric_literal">1</span><span class="attribute">}</span><span class="string_literal"> is </span><span class="attribute">{</span><span class="numeric_literal">2</span><span class="attribute">:</span><span class="attribute">.</span><span class="numeric_literal">0</span><span class="attribute">$</span><span class="attribute">}</span><span class="string_literal">"</span>, <span class="numeric_literal">5</span>, <span class="string_literal">"x"</span>, <span class="numeric_literal">0.01</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="numeric_literal">0</span><span class="attribute">}</span><span class="string_literal"> is </span><span class="attribute">{</span><span class="numeric_literal">2</span><span class="attribute">:</span><span class="attribute">.</span><span class="numeric_literal">1</span><span class="attribute">$</span><span class="attribute">}</span><span class="string_literal">"</span>, <span class="string_literal">"x"</span>, <span class="numeric_literal">5</span>, <span class="numeric_literal">0.01</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal"> is </span><span class="attribute">{</span><span class="attribute">:</span><span class="attribute">.</span><span class="attribute">*</span><span class="attribute">}</span><span class="string_literal">"</span>,    <span class="string_literal">"x"</span>, <span class="numeric_literal">5</span>, <span class="numeric_literal">0.01</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal"> is </span><span class="attribute">{</span><span class="numeric_literal">2</span><span class="attribute">:</span><span class="attribute">.</span><span class="attribute">*</span><span class="attribute">}</span><span class="string_literal">"</span>,   <span class="string_literal">"x"</span>, <span class="numeric_literal">5</span>, <span class="numeric_literal">0.01</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal"> is </span><span class="attribute">{</span><span class="variable">number</span><span class="attribute">:</span><span class="attribute">.</span><span class="variable">prec</span><span class="attribute">$</span><span class="attribute">}</span><span class="string_literal">"</span>, <span class="string_literal">"x"</span>, prec = <span class="numeric_literal">5</span>, number = <span class="numeric_literal">0.01</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal">, `</span><span class="attribute">{</span><span class="variable">name</span><span class="attribute">:</span><span class="attribute">.</span><span class="attribute">*</span><span class="attribute">}</span><span class="string_literal">` has 3 fractional digits"</span>, <span class="string_literal">"Hello"</span>, <span class="numeric_literal">3</span>, name=<span class="numeric_literal">1234.56</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal">, `</span><span class="attribute">{</span><span class="variable">name</span><span class="attribute">:</span><span class="attribute">.</span><span class="attribute">*</span><span class="attribute">}</span><span class="string_literal">` has 3 characters"</span>, <span class="string_literal">"Hello"</span>, <span class="numeric_literal">3</span>, name=<span class="string_literal">"1234.56"</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal">, `</span><span class="attribute">{</span><span class="variable">name</span><span class="attribute">:</span><span class="attribute">&gt;</span><span class="numeric_literal">8</span><span class="attribute">.</span><span class="attribute">*</span><span class="attribute">}</span><span class="string_literal">` has 3 right-aligned characters"</span>, <span class="string_literal">"Hello"</span>, <span class="numeric_literal">3</span>, name=<span class="string_literal">"1234.56"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello, </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"world"</span>);   <span class="comment">// =&gt; "Hello, world!"</span>
+    <span class="macro">println!</span>(<span class="string_literal">"The number is </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">"</span>, <span class="numeric_literal">1</span>);   <span class="comment">// =&gt; "The number is 1"</span>
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">?</span><span class="format_specifier">}</span><span class="string_literal">"</span>, (<span class="numeric_literal">3</span>, <span class="numeric_literal">4</span>));          <span class="comment">// =&gt; "(3, 4)"</span>
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="variable">value</span><span class="format_specifier">}</span><span class="string_literal">"</span>, value=<span class="numeric_literal">4</span>);      <span class="comment">// =&gt; "4"</span>
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal"> </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">"</span>, <span class="numeric_literal">1</span>, <span class="numeric_literal">2</span>);           <span class="comment">// =&gt; "1 2"</span>
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="numeric_literal">0</span><span class="numeric_literal">4</span><span class="format_specifier">}</span><span class="string_literal">"</span>, <span class="numeric_literal">42</span>);             <span class="comment">// =&gt; "0042" with leading zerosV</span>
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="numeric_literal">1</span><span class="format_specifier">}</span><span class="string_literal"> </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal"> </span><span class="format_specifier">{</span><span class="numeric_literal">0</span><span class="format_specifier">}</span><span class="string_literal"> </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">"</span>, <span class="numeric_literal">1</span>, <span class="numeric_literal">2</span>);   <span class="comment">// =&gt; "2 1 1 2"</span>
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="variable">argument</span><span class="format_specifier">}</span><span class="string_literal">"</span>, argument = <span class="string_literal">"test"</span>);   <span class="comment">// =&gt; "test"</span>
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="variable">name</span><span class="format_specifier">}</span><span class="string_literal"> </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">"</span>, <span class="numeric_literal">1</span>, name = <span class="numeric_literal">2</span>);          <span class="comment">// =&gt; "2 1"</span>
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="variable">a</span><span class="format_specifier">}</span><span class="string_literal"> </span><span class="format_specifier">{</span><span class="variable">c</span><span class="format_specifier">}</span><span class="string_literal"> </span><span class="format_specifier">{</span><span class="variable">b</span><span class="format_specifier">}</span><span class="string_literal">"</span>, a=<span class="string_literal">"a"</span>, b=<span class="char_literal">'b'</span>, c=<span class="numeric_literal">3</span>);  <span class="comment">// =&gt; "a 3 b"</span>
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="numeric_literal">5</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="numeric_literal">1</span><span class="format_specifier">$</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>, <span class="numeric_literal">5</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="numeric_literal">1</span><span class="format_specifier">:</span><span class="numeric_literal">0</span><span class="format_specifier">$</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="numeric_literal">5</span>, <span class="string_literal">"x"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="variable">width</span><span class="format_specifier">$</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>, width = <span class="numeric_literal">5</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">&lt;</span><span class="numeric_literal">5</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">-</span><span class="format_specifier">&lt;</span><span class="numeric_literal">5</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">^</span><span class="numeric_literal">5</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">&gt;</span><span class="numeric_literal">5</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"x"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">+</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="numeric_literal">5</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">#</span><span class="variable">x</span><span class="string_literal">}!"</span>, <span class="numeric_literal">27</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="numeric_literal">0</span><span class="numeric_literal">5</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="numeric_literal">5</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="numeric_literal">0</span><span class="numeric_literal">5</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, -<span class="numeric_literal">5</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">#</span><span class="numeric_literal">0</span><span class="numeric_literal">10</span><span class="variable">x</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="numeric_literal">27</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="numeric_literal">0</span><span class="format_specifier">}</span><span class="string_literal"> is </span><span class="format_specifier">{</span><span class="numeric_literal">1</span><span class="format_specifier">:</span><span class="format_specifier">.</span><span class="numeric_literal">5</span><span class="format_specifier">}</span><span class="string_literal">"</span>, <span class="string_literal">"x"</span>, <span class="numeric_literal">0.01</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="numeric_literal">1</span><span class="format_specifier">}</span><span class="string_literal"> is </span><span class="format_specifier">{</span><span class="numeric_literal">2</span><span class="format_specifier">:</span><span class="format_specifier">.</span><span class="numeric_literal">0</span><span class="format_specifier">$</span><span class="format_specifier">}</span><span class="string_literal">"</span>, <span class="numeric_literal">5</span>, <span class="string_literal">"x"</span>, <span class="numeric_literal">0.01</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="numeric_literal">0</span><span class="format_specifier">}</span><span class="string_literal"> is </span><span class="format_specifier">{</span><span class="numeric_literal">2</span><span class="format_specifier">:</span><span class="format_specifier">.</span><span class="numeric_literal">1</span><span class="format_specifier">$</span><span class="format_specifier">}</span><span class="string_literal">"</span>, <span class="string_literal">"x"</span>, <span class="numeric_literal">5</span>, <span class="numeric_literal">0.01</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal"> is </span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">.</span><span class="format_specifier">*</span><span class="format_specifier">}</span><span class="string_literal">"</span>,    <span class="string_literal">"x"</span>, <span class="numeric_literal">5</span>, <span class="numeric_literal">0.01</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal"> is </span><span class="format_specifier">{</span><span class="numeric_literal">2</span><span class="format_specifier">:</span><span class="format_specifier">.</span><span class="format_specifier">*</span><span class="format_specifier">}</span><span class="string_literal">"</span>,   <span class="string_literal">"x"</span>, <span class="numeric_literal">5</span>, <span class="numeric_literal">0.01</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"Hello </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal"> is </span><span class="format_specifier">{</span><span class="variable">number</span><span class="format_specifier">:</span><span class="format_specifier">.</span><span class="variable">prec</span><span class="format_specifier">$</span><span class="format_specifier">}</span><span class="string_literal">"</span>, <span class="string_literal">"x"</span>, prec = <span class="numeric_literal">5</span>, number = <span class="numeric_literal">0.01</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">, `</span><span class="format_specifier">{</span><span class="variable">name</span><span class="format_specifier">:</span><span class="format_specifier">.</span><span class="format_specifier">*</span><span class="format_specifier">}</span><span class="string_literal">` has 3 fractional digits"</span>, <span class="string_literal">"Hello"</span>, <span class="numeric_literal">3</span>, name=<span class="numeric_literal">1234.56</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">, `</span><span class="format_specifier">{</span><span class="variable">name</span><span class="format_specifier">:</span><span class="format_specifier">.</span><span class="format_specifier">*</span><span class="format_specifier">}</span><span class="string_literal">` has 3 characters"</span>, <span class="string_literal">"Hello"</span>, <span class="numeric_literal">3</span>, name=<span class="string_literal">"1234.56"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">, `</span><span class="format_specifier">{</span><span class="variable">name</span><span class="format_specifier">:</span><span class="format_specifier">&gt;</span><span class="numeric_literal">8</span><span class="format_specifier">.</span><span class="format_specifier">*</span><span class="format_specifier">}</span><span class="string_literal">` has 3 right-aligned characters"</span>, <span class="string_literal">"Hello"</span>, <span class="numeric_literal">3</span>, name=<span class="string_literal">"1234.56"</span>);
     <span class="macro">println!</span>(<span class="string_literal">"Hello {{}}"</span>);
     <span class="macro">println!</span>(<span class="string_literal">"{{ Hello"</span>);
 
-    <span class="macro">println!</span>(<span class="string_literal">r"Hello, </span><span class="attribute">{</span><span class="attribute">}</span><span class="string_literal">!"</span>, <span class="string_literal">"world"</span>);
+    <span class="macro">println!</span>(<span class="string_literal">r"Hello, </span><span class="format_specifier">{</span><span class="format_specifier">}</span><span class="string_literal">!"</span>, <span class="string_literal">"world"</span>);
 
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="variable">\x41</span><span class="attribute">}</span><span class="string_literal">"</span>, A = <span class="numeric_literal">92</span>);
-    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="attribute">{</span><span class="variable">ничоси</span><span class="attribute">}</span><span class="string_literal">"</span>, ничоси = <span class="numeric_literal">92</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="variable">\x41</span><span class="format_specifier">}</span><span class="string_literal">"</span>, A = <span class="numeric_literal">92</span>);
+    <span class="macro">println!</span>(<span class="string_literal">"</span><span class="format_specifier">{</span><span class="variable">ничоси</span><span class="format_specifier">}</span><span class="string_literal">"</span>, ничоси = <span class="numeric_literal">92</span>);
 }</code></pre>
\ No newline at end of file
diff --git a/crates/ra_ide/src/snapshots/highlighting.html b/crates/ra_ide/src/snapshots/highlighting.html
index ccb1fc751..4b12fe823 100644
--- a/crates/ra_ide/src/snapshots/highlighting.html
+++ b/crates/ra_ide/src/snapshots/highlighting.html
@@ -20,6 +20,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .macro              { color: #94BFF3; }
 .module             { color: #AFD8AF; }
 .variable           { color: #DCDCCC; }
+.format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
diff --git a/crates/ra_ide/src/snapshots/rainbow_highlighting.html b/crates/ra_ide/src/snapshots/rainbow_highlighting.html
index 3df82c45f..11e1f3e44 100644
--- a/crates/ra_ide/src/snapshots/rainbow_highlighting.html
+++ b/crates/ra_ide/src/snapshots/rainbow_highlighting.html
@@ -20,6 +20,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .macro              { color: #94BFF3; }
 .module             { color: #AFD8AF; }
 .variable           { color: #DCDCCC; }
+.format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
diff --git a/crates/ra_ide/src/syntax_highlighting.rs b/crates/ra_ide/src/syntax_highlighting.rs
index be0f8c827..6658c7bb2 100644
--- a/crates/ra_ide/src/syntax_highlighting.rs
+++ b/crates/ra_ide/src/syntax_highlighting.rs
@@ -290,7 +290,7 @@ fn highlight_format_specifier(kind: FormatSpecifier) -> Option<HighlightTag> {
         | FormatSpecifier::DollarSign
         | FormatSpecifier::Dot
         | FormatSpecifier::Asterisk
-        | FormatSpecifier::QuestionMark => HighlightTag::Attribute,
+        | FormatSpecifier::QuestionMark => HighlightTag::FormatSpecifier,
         FormatSpecifier::Integer | FormatSpecifier::Zero => HighlightTag::NumericLiteral,
         FormatSpecifier::Identifier => HighlightTag::Local,
     })
diff --git a/crates/ra_ide/src/syntax_highlighting/html.rs b/crates/ra_ide/src/syntax_highlighting/html.rs
index 010db4017..ff0eeeb52 100644
--- a/crates/ra_ide/src/syntax_highlighting/html.rs
+++ b/crates/ra_ide/src/syntax_highlighting/html.rs
@@ -79,6 +79,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 .macro              { color: #94BFF3; }
 .module             { color: #AFD8AF; }
 .variable           { color: #DCDCCC; }
+.format_specifier   { color: #CC696B; }
 .mutable            { text-decoration: underline; }
 
 .keyword            { color: #F0DFAF; font-weight: bold; }
diff --git a/crates/ra_ide/src/syntax_highlighting/tags.rs b/crates/ra_ide/src/syntax_highlighting/tags.rs
index f2c421654..be1a0f12b 100644
--- a/crates/ra_ide/src/syntax_highlighting/tags.rs
+++ b/crates/ra_ide/src/syntax_highlighting/tags.rs
@@ -39,6 +39,7 @@ pub enum HighlightTag {
     Union,
     Local,
     UnresolvedReference,
+    FormatSpecifier,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
@@ -81,6 +82,7 @@ impl HighlightTag {
             HighlightTag::Union => "union",
             HighlightTag::Local => "variable",
             HighlightTag::UnresolvedReference => "unresolved_reference",
+            HighlightTag::FormatSpecifier => "format_specifier",
         }
     }
 }