Rollup merge of #55013 - matthewjasper:propagate-generator-bounds, r=nikomatsakis

[NLL] Propagate bounds from generators

This used to only be done for closures.

src/test/ui/generator/generator-region-requirements.ast.stderr

@@ -0,0 +1,12 @@
+error[E0621]: explicit lifetime required in the type of `x`
+  --> $DIR/generator-region-requirements.rs:15:51
+   |
+LL | fn dangle(x: &mut i32) -> &'static mut i32 {
+   |              -------- help: add explicit lifetime `'static` to the type of `x`: `&'static mut i32`
+...
+LL |             GeneratorState::Complete(c) => return c,
+   |                                                   ^ lifetime `'static` required
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0621`.

src/test/ui/generator/generator-region-requirements.nll.stderr

@@ -0,0 +1,12 @@
+error[E0621]: explicit lifetime required in the type of `x`
+  --> $DIR/generator-region-requirements.rs:11:9
+   |
+LL | fn dangle(x: &mut i32) -> &'static mut i32 {
+   |              -------- help: add explicit lifetime `'static` to the type of `x`: `&'static mut i32`
+...
+LL |         x
+   |         ^ lifetime `'static` required
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0621`.

src/test/ui/generator/generator-region-requirements.rs

@@ -0,0 +1,21 @@
+// revisions: ast nll
+// ignore-compare-mode-nll
+
+#![feature(generators, generator_trait)]
+#![cfg_attr(nll, feature(nll))]
+use std::ops::{Generator, GeneratorState};
+
+fn dangle(x: &mut i32) -> &'static mut i32 {
+    let mut g = || {
+        yield;
+        x
+    };
+    loop {
+        match unsafe { g.resume() } {
+            GeneratorState::Complete(c) => return c,
+            GeneratorState::Yielded(_) => (),
+        }
+    }
+}
+
+fn main() {}