Hover tooltip module name is monospace once again

The line separator is moved below the function signature to split
regions between the docs. This is very similar to how IntelliJ
displays tooltips. Adding an additional separator between the module
name and function signature currently has rendering issues.

Fixes #4594
Alternative to #4615

crates/ra_ide/src/display.rs

@@ -83,12 +83,13 @@ pub(crate) fn rust_code_markup_with_doc(
 
     if let Some(mod_path) = mod_path {
         if !mod_path.is_empty() {
-            format_to!(buf, "{}\n___\n\n", mod_path);
+            format_to!(buf, "```rust\n{}\n```\n\n", mod_path);
         }
     }
     format_to!(buf, "```rust\n{}\n```", code);
 
     if let Some(doc) = doc {
+        format_to!(buf, "\n___");
         format_to!(buf, "\n\n{}", doc);
     }
 

crates/ra_ide/src/hover.rs

@@ -405,7 +405,7 @@ mod tests {
                 };
             }
         "#,
-            &["Foo\n___\n\n```rust\nfield_a: u32"],
+            &["Foo\n```\n\n```rust\nfield_a: u32"],
         );
 
         // Hovering over the field in the definition
@@ -422,7 +422,7 @@ mod tests {
                 };
             }
         "#,
-            &["Foo\n___\n\n```rust\nfield_a: u32"],
+            &["Foo\n```\n\n```rust\nfield_a: u32"],
         );
     }
 
@@ -475,7 +475,7 @@ fn main() {
             ",
         );
         let hover = analysis.hover(position).unwrap().unwrap();
-        assert_eq!(trim_markup_opt(hover.info.first()), Some("Option\n___\n\n```rust\nSome"));
+        assert_eq!(trim_markup_opt(hover.info.first()), Some("Option\n```\n\n```rust\nSome"));
 
         let (analysis, position) = single_file_with_position(
             "
@@ -503,11 +503,12 @@ fn main() {
         "#,
             &["
 Option
-___
+```
 
 ```rust
 None
 ```
+___
 
 The None variant
             "
@@ -527,11 +528,12 @@ The None variant
         "#,
             &["
 Option
-___
+```
 
 ```rust
 Some
 ```
+___
 
 The Some variant
             "
@@ -614,7 +616,7 @@ fn func(foo: i32) { if true { <|>foo; }; }
         let hover = analysis.hover(position).unwrap().unwrap();
         assert_eq!(
             trim_markup_opt(hover.info.first()),
-            Some("wrapper::Thing\n___\n\n```rust\nfn new() -> Thing")
+            Some("wrapper::Thing\n```\n\n```rust\nfn new() -> Thing")
         );
     }
 
@@ -891,7 +893,7 @@ fn func(foo: i32) { if true { <|>foo; }; }
                 fo<|>o();
             }
             ",
-            &["fn foo()\n```\n\n<- `\u{3000}` here"],
+            &["fn foo()\n```\n___\n\n<- `\u{3000}` here"],
         );
     }
 

crates/rust-analyzer/tests/heavy_tests/main.rs

@@ -756,5 +756,5 @@ pub fn foo(_input: TokenStream) -> TokenStream {
     });
 
     let value = res.get("contents").unwrap().get("value").unwrap().to_string();
-    assert_eq!(value, r#""foo::Bar\n___\n\n```rust\nfn bar()\n```""#)
+    assert_eq!(value, r#""```rust\nfoo::Bar\n```\n\n```rust\nfn bar()\n```""#)
 }