From 92197a551f8210d9f7d8658f60d738e4ea3c7dd6 Mon Sep 17 00:00:00 2001 From: Taylor Yu Date: Sat, 19 Jun 2021 15:28:32 -0500 Subject: [PATCH] E0716: clarify that equivalent code example is erroneous In E0716, there is a code block that is equivalent to the erroneous code example. Especially when viewed with `rustc --explain`, it's not obvious that it is also erroneous, and some users have been confused when they try to change their code to match the erroneous equivalent. --- compiler/rustc_error_codes/src/error_codes/E0716.md | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/compiler/rustc_error_codes/src/error_codes/E0716.md b/compiler/rustc_error_codes/src/error_codes/E0716.md index c6d0337ddda56..c3546cd744f7b 100644 --- a/compiler/rustc_error_codes/src/error_codes/E0716.md +++ b/compiler/rustc_error_codes/src/error_codes/E0716.md @@ -14,14 +14,16 @@ Here, the expression `&foo()` is borrowing the expression `foo()`. As `foo()` is a call to a function, and not the name of a variable, this creates a **temporary** -- that temporary stores the return value from `foo()` so that it can be borrowed. You could imagine that `let p = bar(&foo());` is equivalent to -this: +the following, which uses an explicit temporary variable. + +Erroneous code example: ```compile_fail,E0597 # fn foo() -> i32 { 22 } # fn bar(x: &i32) -> &i32 { x } let p = { let tmp = foo(); // the temporary - bar(&tmp) + bar(&tmp) // error: `tmp` does not live long enough }; // <-- tmp is freed as we exit this block let q = p; ```