Rollup merge of #161369 - KevinA-cpu:regression-test-79033, r=TaKO8Ki

Add regression test for confusing lifetime error message issue

closes #79033

Author: jhpratt

tests/ui/impl-trait/confusing-lifetime-error-issue-79033.rs

@@ -0,0 +1,36 @@
+// Regression test for https://github.com/rust-lang/rust/issues/79033/
+// rustc should be clear about the lifetime issue below where
+// self is borrowed for the duration of the returned iterator
+// but the lifetime of self will end when fn lines() returns.
+//@ edition: 2024
+
+#[derive(Debug, Clone, Copy)]
+pub struct Location<'a> {
+    pub filename: &'a str,
+    pub start: LocationHalf,
+    pub end: LocationHalf,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct LocationHalf {
+    pub line: u32,
+    pub column: u32,
+}
+
+impl Location<'_> {
+    /// Returns an iterator over the line numbers and lines of this location.
+    pub fn lines<'a>(self, source: &'a str) -> impl Iterator<Item = (u32, &'a str)> {
+        let lines = source.split('\n');
+        lines.enumerate().filter_map(|(i, line)| {
+        //~^ ERROR closure may outlive the current function, but it borrows `self.start.line`, which is owned by the current function
+        //~| ERROR closure may outlive the current function, but it borrows `self.end.line`, which is owned by the current function
+            if self.start.line as usize <= i && i <= self.end.line as usize {
+                Some((i as u32 + 1, line))
+            } else {
+                None
+            }
+        })
+    }
+}
+
+fn main() {}

tests/ui/impl-trait/confusing-lifetime-error-issue-79033.stderr

@@ -0,0 +1,51 @@
+error[E0373]: closure may outlive the current function, but it borrows `self.start.line`, which is owned by the current function
+  --> $DIR/confusing-lifetime-error-issue-79033.rs:24:38
+   |
+LL |         lines.enumerate().filter_map(|(i, line)| {
+   |                                      ^^^^^^^^^^^ may outlive borrowed value `self.start.line`
+...
+LL |             if self.start.line as usize <= i && i <= self.end.line as usize {
+   |                --------------- `self.start.line` is borrowed here
+   |
+note: function requires argument type to outlive `'static`
+  --> $DIR/confusing-lifetime-error-issue-79033.rs:24:9
+   |
+LL | /         lines.enumerate().filter_map(|(i, line)| {
+LL | |
+LL | |
+LL | |             if self.start.line as usize <= i && i <= self.end.line as usize {
+...  |
+LL | |         })
+   | |__________^
+help: to force the closure to take ownership of `self.start.line` (and any other referenced variables), use the `move` keyword
+   |
+LL |         lines.enumerate().filter_map(move |(i, line)| {
+   |                                      ++++
+
+error[E0373]: closure may outlive the current function, but it borrows `self.end.line`, which is owned by the current function
+  --> $DIR/confusing-lifetime-error-issue-79033.rs:24:38
+   |
+LL |         lines.enumerate().filter_map(|(i, line)| {
+   |                                      ^^^^^^^^^^^ may outlive borrowed value `self.end.line`
+...
+LL |             if self.start.line as usize <= i && i <= self.end.line as usize {
+   |                                                      ------------- `self.end.line` is borrowed here
+   |
+note: function requires argument type to outlive `'static`
+  --> $DIR/confusing-lifetime-error-issue-79033.rs:24:9
+   |
+LL | /         lines.enumerate().filter_map(|(i, line)| {
+LL | |
+LL | |
+LL | |             if self.start.line as usize <= i && i <= self.end.line as usize {
+...  |
+LL | |         })
+   | |__________^
+help: to force the closure to take ownership of `self.end.line` (and any other referenced variables), use the `move` keyword
+   |
+LL |         lines.enumerate().filter_map(move |(i, line)| {
+   |                                      ++++
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0373`.