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+[[Rust]]
+[[Data must outlive any references to it]]
+
+Associated permission: Flow:
+Indicates whether or not a reference argument is allowed to be used, or a reference is allowed to be returned.
+
+Simple example:
+```rust
+fn a_or_b(a: &str, b: &str) -> &str {
+	if something {
+		a
+	} else {
+		b
+	}
+}
+
+let a = vec![];
+let b = String::from("a");
+let c = a_or_b(&a, &b);
+drop(b);
+println!("{}", c);
+```
+
+In the above example `c` is being printed after `b` is dropped but `a_or_b` could have returned `b` so the println uses freed data ( null pointer exception) .
+
+It is also not possible to return a reference to heap data that will be dropped at the end of the function.
+
+```rust
+fn epic_ref() -> &str {
+	let cool = String::from("yo");
+	let coolref = &cool;
+	coolref
+}
+```
+^ will fail
+\ No newline at end of file