Auto merge of #138947 - madsmtm:refactor-apple-versions, r=Noratrieb

Refactor Apple version handling in the compiler

Move various Apple version handling code in the compiler out `rustc_codegen_ssa` and into a place where it can be accessed by `rustc_attr_parsing`, which I found to be necessary when doing https://github.com/rust-lang/rust/pull/136867. Thought I'd split it out to make it easier to land, and to make further changes like https://github.com/rust-lang/rust/pull/131477 have fewer conflicts / PR dependencies.

There should be no functional changes in this PR.

`@rustbot` label O-apple
r? rust-lang/compiler

1 files changed, 9 insertions, 1 deletions

diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index 3979aea70d3..bf95014843d 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -1,4 +1,4 @@
-use std::num::NonZero;
+use std::num::{NonZero, ParseIntError};
 
 use rustc_ast::token;
 use rustc_ast::util::literal::LitError;
@@ -14,6 +14,14 @@ use rustc_target::spec::{SplitDebuginfo, StackProtector, TargetTuple};
 use crate::config::CrateType;
 use crate::parse::ParseSess;
 
+#[derive(Diagnostic)]
+pub(crate) enum AppleDeploymentTarget {
+    #[diag(session_apple_deployment_target_invalid)]
+    Invalid { env_var: &'static str, error: ParseIntError },
+    #[diag(session_apple_deployment_target_too_low)]
+    TooLow { env_var: &'static str, version: String, os_min: String },
+}
+
 pub(crate) struct FeatureGateError {
     pub(crate) span: MultiSpan,
     pub(crate) explain: DiagMessage,