Merge #4787

4787: Fix bug in lexer for format specifier r=matklad a=ltentrup

The `type` and `width` were not correctly distinguished.
Fixes #4696.

Co-authored-by: Leander Tentrup <leander.tentrup@gmail.com>

Author: bors[bot]

crates/ra_ide/src/snapshots/highlight_strings.html

@@ -63,7 +63,7 @@
     <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">"</span><span class="format_specifier">{</span><span class="format_specifier">:</span><span class="format_specifier">#</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="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>);

crates/ra_syntax/src/ast/tokens.rs

@@ -335,16 +335,26 @@ pub trait HasFormatSpecifier: AstToken {
                             }
                             c if c == '_' || c.is_alphabetic() => {
                                 read_identifier(&mut chars, &mut callback);
-                                if chars.peek().and_then(|next| next.1.as_ref().ok()).copied()
-                                    != Some('$')
-                                {
-                                    continue;
-                                }
-                                skip_char_and_emit(
-                                    &mut chars,
-                                    FormatSpecifier::DollarSign,
-                                    &mut callback,
-                                );
+                                // can be either width (indicated by dollar sign, or type in which case
+                                // the next sign has to be `}`)
+                                let next =
+                                    chars.peek().and_then(|next| next.1.as_ref().ok()).copied();
+                                match next {
+                                    Some('$') => skip_char_and_emit(
+                                        &mut chars,
+                                        FormatSpecifier::DollarSign,
+                                        &mut callback,
+                                    ),
+                                    Some('}') => {
+                                        skip_char_and_emit(
+                                            &mut chars,
+                                            FormatSpecifier::Close,
+                                            &mut callback,
+                                        );
+                                        continue;
+                                    }
+                                    _ => continue,
+                                };
                             }
                             _ => {}
                         }
@@ -416,12 +426,11 @@ pub trait HasFormatSpecifier: AstToken {
                         }
                     }
 
-                    let mut cloned = chars.clone().take(2);
-                    let first = cloned.next().and_then(|next| next.1.as_ref().ok()).copied();
-                    if first != Some('}') {
+                    if let Some((_, Ok('}'))) = chars.peek() {
+                        skip_char_and_emit(&mut chars, FormatSpecifier::Close, &mut callback);
+                    } else {
                         continue;
                     }
-                    skip_char_and_emit(&mut chars, FormatSpecifier::Close, &mut callback);
                 }
                 _ => {
                     while let Some((_, Ok(next_char))) = chars.peek() {