Fix raw block has extra space when end with backtick (#4162)

Co-authored-by: Laurenz <laurmaedje@gmail.com>

crates/typst-syntax/src/lexer.rs

@@ -297,16 +297,12 @@ impl Lexer<'_> {
             self.push_raw(SyntaxKind::RawLang);
         }
 
-        // Determine inner content between backticks and with trimmed
+        // Determine inner content between backticks.
-        // single spaces (line trimming comes later).
         self.s.eat_if(' ');
-        let mut inner = self.s.to(end - backticks);
+        let inner = self.s.to(end - backticks);
-        if inner.trim_end().ends_with('`') {
-            inner = inner.strip_suffix(' ').unwrap_or(inner);
-        }
 
         // Determine dedent level.
-        let lines = split_newlines(inner);
+        let mut lines = split_newlines(inner);
         let dedent = lines
             .iter()
             .skip(1)
@@ -317,6 +313,15 @@ impl Lexer<'_> {
             .min()
             .unwrap_or(0);
 
+        // Trim single space in last line if text ends with a backtick. The last
+        // line is the one directly before the closing backticks and if it is
+        // just whitespace, it will be completely trimmed below.
+        if inner.trim_end().ends_with('`') {
+            if let Some(last) = lines.last_mut() {
+                *last = last.strip_suffix(' ').unwrap_or(last);
+            }
+        }
+
         let is_whitespace = |line: &&str| line.chars().all(char::is_whitespace);
         let starts_whitespace = lines.first().is_some_and(is_whitespace);
         let ends_whitespace = lines.last().is_some_and(is_whitespace);

tests/suite/text/raw.typ

@@ -624,7 +624,20 @@ fn main() {
 
 ~~~~The~spaces~on~this~line~shrink
 
+--- issue-3820-raw-space-when-end-with-backtick ---
+```typ
+`code`
+```
+
+  ```typ
+  `code`
+  ```
+
 --- raw-unclosed ---
-// Unterminated.
+// Test unterminated raw text.
+//
+// Note: This test should be the final one in the file because it messes up
+// syntax highlighting.
+//
 // Error: 1-2:1 unclosed raw text
 `endless