Merge #6472

6472: Add `static` modifier for associated functions r=matklad a=p3achyjr

Adds static semantic token modifier to associated functions, resolves #6194 

## Info

- Associated functions are more-or-less equivalent to static methods in other languages. This PR checks, for each function, whether that function has a self_param, and whether it's enclosed in a trait/impl.

## Changes

- Added method ```is_associated``` to code_model::Function. This basically gets the source from the ast, and checks whether the enclosing scope is an impl or trait.
- Added `static` to HighlightModifiers
- Added unit test

## Tests

- Ran ```cargo test```

Co-authored-by: Anatol Liu <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/crates/ide/src/syntax_highlighting/test_data/highlight_injection.html b/crates/ide/src/syntax_highlighting/test_data/highlight_injection.html
index 18addd00d..57c178916 100644
--- a/crates/ide/src/syntax_highlighting/test_data/highlight_injection.html
+++ b/crates/ide/src/syntax_highlighting/test_data/highlight_injection.html
@@ -40,7 +40,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 <span class="keyword">fn</span> <span class="function declaration">main</span><span class="punctuation">(</span><span class="punctuation">)</span> <span class="punctuation">{</span>
     <span class="function">fixture</span><span class="punctuation">(</span><span class="string_literal">r#"</span>
         <span class="keyword">trait</span> <span class="trait declaration">Foo</span> <span class="punctuation">{</span>
-            <span class="keyword">fn</span> <span class="function declaration">foo</span><span class="punctuation">(</span><span class="punctuation">)</span> <span class="punctuation">{</span>
+            <span class="keyword">fn</span> <span class="function declaration static">foo</span><span class="punctuation">(</span><span class="punctuation">)</span> <span class="punctuation">{</span>
                 <span class="macro">println!</span><span class="punctuation">(</span><span class="string_literal">"2 + 2 = {}"</span><span class="punctuation">,</span> <span class="numeric_literal">4</span><span class="punctuation">)</span><span class="punctuation">;</span>
             <span class="punctuation">}</span>
         <span class="punctuation">}</span><span class="string_literal">"#</span>