Slice indexing in long chains is separated from target element

[Sindisil]

Formatting of slice indexing on an element in a long chain sometimes separates the index from the indexed element. See lines 299 & 300 below, where 'text' is a String member of the specified buffer line:

287	    fn handle_left(&mut self) -> ControlFlow<()> {
288	        if self.cursor.index == self.input_start {
289	            return ControlFlow::Continue(());
290	        }
291	
292	        if self.cursor.index.offset == 0 {
293	            self.cursor.index.line -= 1;
294	            self.cursor.index.offset = self.buffer[self.cursor.index.line].len();
295	            self.cursor.column = self.buffer[self.cursor.index.line].width;
296	            self.cursor.line -= 1;
297	        }
298	
299	        if let Some((prev_idx, prev_width)) = self.buffer[self.cursor.index.line].text
300	            [..self.cursor.index.offset]
301	            .char_indices()
302	            .map(|(i, c)| (i, c.width().unwrap_or(0)))
303	            .rfind(|(_, w)| *w > 0)
304	        {
305	            self.cursor.index.offset = prev_idx;
306	            self.cursor.column -= prev_width;
307	        }
308	
309	        self.adjust_viewport();
310	        ControlFlow::Continue(())
311	    }

Per the section of the style guide on array accesses, indexing, and slicing, I would have expected that if let expression to instead be formatted as below:

299	        if let Some((prev_idx, prev_width)) = self.buffer[self.cursor.index.line]
300	            .text[..self.cursor.index.offset]
301	            .char_indices()
302	            .map(|(i, c)| (i, c.width().unwrap_or(0)))
303	            .rfind(|(_, w)| *w > 0)
304	        {
305	            self.cursor.index.offset = prev_idx;
306	            self.cursor.column -= prev_width;
307	        }

I first saw this running with max_width = 80, but this example was obtained running w/o any config file (i.e., the stock 100).

Version in use:

$ cargo --version
cargo 1.80.0-beta.4 (34a6a87d8 2024-06-04)
$ rustfmt --version
rustfmt 1.7.0-beta (64a1fe6 2024-06-21)

[ytmimi]

Thanks for the report.

Per the section of the style guide on array accesses, indexing, and slicing, I would have expected that if let expression to instead be formatted as below:

When you get a chance, would you mind linking to the section of the style guide that you're referring to.

[Sindisil]

Sure: Array accesses, indexing, and slicing

Sorry 'bout that -- I should have included a link in my report.