Fix crash due to consecutive weak spacing (#5562)

crates/typst-layout/src/inline/collect.rs

@@ -256,8 +256,7 @@ impl<'a> Collector<'a> {
     }
 
     fn push_text(&mut self, text: &str, styles: StyleChain<'a>) {
-        self.full.push_str(text);
-        self.push_segment(Segment::Text(text.len(), styles));
+        self.build_text(styles, |full| full.push_str(text));
     }
 
     fn build_text<F>(&mut self, styles: StyleChain<'a>, f: F)
@@ -266,33 +265,33 @@ impl<'a> Collector<'a> {
     {
         let prev = self.full.len();
         f(&mut self.full);
-        let len = self.full.len() - prev;
-        self.push_segment(Segment::Text(len, styles));
+        let segment_len = self.full.len() - prev;
+
+        // Merge adjacent text segments with the same styles.
+        if let Some(Segment::Text(last_len, last_styles)) = self.segments.last_mut() {
+            if *last_styles == styles {
+                *last_len += segment_len;
+                return;
+            }
+        }
+
+        self.segments.push(Segment::Text(segment_len, styles));
     }
 
     fn push_item(&mut self, item: Item<'a>) {
-        self.full.push_str(item.textual());
-        self.push_segment(Segment::Item(item));
-    }
-
-    fn push_segment(&mut self, segment: Segment<'a>) {
-        match (self.segments.last_mut(), &segment) {
-            // Merge adjacent text segments with the same styles.
-            (Some(Segment::Text(last_len, last_styles)), Segment::Text(len, styles))
-                if *last_styles == *styles =>
-            {
-                *last_len += *len;
-            }
-
+        match (self.segments.last_mut(), &item) {
             // Merge adjacent weak spacing by taking the maximum.
             (
                 Some(Segment::Item(Item::Absolute(prev_amount, true))),
-                Segment::Item(Item::Absolute(amount, true)),
+                Item::Absolute(amount, true),
             ) => {
                 *prev_amount = (*prev_amount).max(*amount);
             }
 
-            _ => self.segments.push(segment),
+            _ => {
+                self.full.push_str(item.textual());
+                self.segments.push(Segment::Item(item));
+            }
         }
     }
 }

crates/typst-layout/src/inline/linebreak.rs

@@ -971,11 +971,13 @@ where
     }
 
     /// Estimates the metrics for the line spanned by the range.
+    #[track_caller]
     fn estimate(&self, range: Range) -> T {
         self.get(range.end) - self.get(range.start)
     }
 
     /// Get the metric at the given byte position.
+    #[track_caller]
     fn get(&self, index: usize) -> T {
         match index.checked_sub(1) {
             None => T::default(),

tests/suite/layout/spacing.typ

@@ -58,3 +58,21 @@ This is the first line \ #h(2cm, weak: true) A new line
 
 // Non-weak-spacing, on the other hand, is not removed.
 This is the first line \ #h(2cm, weak: false) A new line
+
+--- issue-5244-consecutive-weak-space ---
+#set par(linebreaks: "optimized")
+#{
+  [A]
+  h(0.3em, weak: true)
+  h(0.3em, weak: true)
+  [B]
+}
+
+--- issue-5244-consecutive-weak-space-heading ---
+#set par(justify: true)
+#set heading(numbering: "I.")
+
+= #h(0.3em, weak: true) test
+
+--- issue-5253-consecutive-weak-space-math ---
+$= thin thin$ a