Avoid inserting imports directly after continuation (#7553)

## Summary

This is extremely rare in practice, but common in the fuzzer issues so
worth fixing quickly.

Closes https://github.com/astral-sh/ruff/issues/7199.

crates/ruff_linter/resources/test/fixtures/pylint/sys_exit_alias_12.py

@@ -0,0 +1,3 @@
+import os \
+
+exit(0)

crates/ruff_linter/src/importer/insertion.rs

@@ -57,7 +57,7 @@ impl<'a> Insertion<'a> {
         let mut location = if let Some(location) = match_docstring_end(body) {
             // If the first token after the docstring is a semicolon, insert after the semicolon as
             // an inline statement.
-            if let Some(offset) = match_leading_semicolon(locator.after(location)) {
+            if let Some(offset) = match_semicolon(locator.after(location)) {
                 return Insertion::inline(" ", location.add(offset).add(TextSize::of(';')), ";");
             }
 
@@ -109,10 +109,14 @@ impl<'a> Insertion<'a> {
         stylist: &Stylist,
     ) -> Insertion<'static> {
         let location = stmt.end();
-        if let Some(offset) = match_leading_semicolon(locator.after(location)) {
+        if let Some(offset) = match_semicolon(locator.after(location)) {
             // If the first token after the statement is a semicolon, insert after the semicolon as
             // an inline statement.
             Insertion::inline(" ", location.add(offset).add(TextSize::of(';')), ";")
+        } else if match_continuation(locator.after(location)).is_some() {
+            // If the first token after the statement is a continuation, insert after the statement
+            // with a semicolon.
+            Insertion::inline("; ", location, "")
         } else {
             // Otherwise, insert on the next line.
             Insertion::own_line(
@@ -289,8 +293,8 @@ fn match_docstring_end(body: &[Stmt]) -> Option<TextSize> {
     Some(stmt.end())
 }
 
-/// If a line starts with a semicolon, return its offset.
-fn match_leading_semicolon(s: &str) -> Option<TextSize> {
+/// If the next token is a semicolon, return its offset.
+fn match_semicolon(s: &str) -> Option<TextSize> {
     for (offset, c) in s.char_indices() {
         match c {
             ' ' | '\t' => continue,
@@ -301,6 +305,18 @@ fn match_leading_semicolon(s: &str) -> Option<TextSize> {
     None
 }
 
+/// If the next token is a continuation (`\`), return its offset.
+fn match_continuation(s: &str) -> Option<TextSize> {
+    for (offset, c) in s.char_indices() {
+        match c {
+            ' ' | '\t' => continue,
+            '\\' => return Some(TextSize::try_from(offset).unwrap()),
+            _ => break,
+        }
+    }
+    None
+}
+
 #[cfg(test)]
 mod tests {
     use anyhow::Result;

crates/ruff_linter/src/rules/pylint/mod.rs

@@ -51,6 +51,7 @@ mod tests {
     #[test_case(Rule::SysExitAlias, Path::new("sys_exit_alias_9.py"))]
     #[test_case(Rule::SysExitAlias, Path::new("sys_exit_alias_10.py"))]
     #[test_case(Rule::SysExitAlias, Path::new("sys_exit_alias_11.py"))]
+    #[test_case(Rule::SysExitAlias, Path::new("sys_exit_alias_12.py"))]
     #[test_case(Rule::ContinueInFinally, Path::new("continue_in_finally.py"))]
     #[test_case(Rule::GlobalStatement, Path::new("global_statement.py"))]
     #[test_case(

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLR1722_sys_exit_alias_12.py.snap

@@ -0,0 +1,20 @@
+---
+source: crates/ruff_linter/src/rules/pylint/mod.rs
+---
+sys_exit_alias_12.py:3:1: PLR1722 [*] Use `sys.exit()` instead of `exit`
+  |
+1 | import os \
+2 | 
+3 | exit(0)
+  | ^^^^ PLR1722
+  |
+  = help: Replace `exit` with `sys.exit()`
+
+ℹ Suggested fix
+1   |-import os \
+  1 |+import os; import sys \
+2 2 | 
+3   |-exit(0)
+  3 |+sys.exit(0)
+
+