Auto merge of #143214 - camsteffen:remove-let-chains-feature, r=est31

Remove let_chains unstable feature

Per https://github.com/rust-lang/rust/issues/53667#issuecomment-3016742982 (but then I also noticed rust-lang/rust#140722)

This replaces the feature gate with a parser error that says let chains require 2024.

A lot of tests were using the unstable feature. I either added edition:2024 to the test or split out the parts that require 2024.

2 files changed, 8 insertions, 1 deletions

diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 0f0c5434800..7f1b0991f0c 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -1779,6 +1779,13 @@ pub(crate) struct AsyncBoundModifierIn2015 {
 }
 
 #[derive(Diagnostic)]
+#[diag(parse_let_chain_pre_2024)]
+pub(crate) struct LetChainPre2024 {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(parse_self_argument_pointer)]
 pub(crate) struct SelfArgumentPointer {
     #[primary_span]
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 3cedc86dc0d..3d89530f914 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -4117,7 +4117,7 @@ impl MutVisitor for CondChecker<'_> {
                         LetChainsPolicy::AlwaysAllowed => (),
                         LetChainsPolicy::EditionDependent { current_edition } => {
                             if !current_edition.at_least_rust_2024() || !span.at_least_rust_2024() {
-                                self.parser.psess.gated_spans.gate(sym::let_chains, span);
+                                self.parser.dcx().emit_err(errors::LetChainPre2024 { span });
                             }
                         }
                     }