From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- .../rustc_error_codes/src/error_codes/E0784.md | 32 ++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 compiler/rustc_error_codes/src/error_codes/E0784.md (limited to 'compiler/rustc_error_codes/src/error_codes/E0784.md') diff --git a/compiler/rustc_error_codes/src/error_codes/E0784.md b/compiler/rustc_error_codes/src/error_codes/E0784.md new file mode 100644 index 000000000..b20b7039b --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0784.md @@ -0,0 +1,32 @@ +A union expression does not have exactly one field. + +Erroneous code example: + +```compile_fail,E0784 +union Bird { + pigeon: u8, + turtledove: u16, +} + +let bird = Bird {}; // error +let bird = Bird { pigeon: 0, turtledove: 1 }; // error +``` + +The key property of unions is that all fields of a union share common storage. +As a result, writes to one field of a union can overwrite its other fields, and +size of a union is determined by the size of its largest field. + +You can find more information about the union types in the [Rust reference]. + +Working example: + +``` +union Bird { + pigeon: u8, + turtledove: u16, +} + +let bird = Bird { pigeon: 0 }; // OK +``` + +[Rust reference]: https://doc.rust-lang.org/reference/items/unions.html -- cgit v1.2.3