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Diffstat (limited to 'compiler/rustc_error_codes/src/error_codes/E0644.md')
-rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0644.md | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0644.md b/compiler/rustc_error_codes/src/error_codes/E0644.md new file mode 100644 index 000000000..8c68da3b2 --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0644.md @@ -0,0 +1,29 @@ +A closure or generator was constructed that references its own type. + +Erroneous code example: + +```compile_fail,E0644 +fn fix<F>(f: &F) + where F: Fn(&F) +{ + f(&f); +} + +fn main() { + fix(&|y| { + // Here, when `x` is called, the parameter `y` is equal to `x`. + }); +} +``` + +Rust does not permit a closure to directly reference its own type, +either through an argument (as in the example above) or by capturing +itself through its environment. This restriction helps keep closure +inference tractable. + +The easiest fix is to rewrite your closure into a top-level function, +or into a method. In some cases, you may also be able to have your +closure call itself by capturing a `&Fn()` object or `fn()` pointer +that refers to itself. That is permitting, since the closure would be +invoking itself via a virtual call, and hence does not directly +reference its own *type*. |