Migrate forbidden_let

compiler/rustc_ast_passes/src/errors.rs

@@ -0,0 +1,32 @@
+//! Errors emitted by ast_passes.
+
+use rustc_errors::fluent;
+use rustc_errors::{AddSubdiagnostic, Diagnostic};
+use rustc_macros::SessionDiagnostic;
+use rustc_span::Span;
+
+use crate::ast_validation::ForbiddenLetReason;
+
+#[derive(SessionDiagnostic)]
+#[error(ast_passes::forbidden_let)]
+#[note]
+pub struct ForbiddenLet {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub(crate) reason: ForbiddenLetReason,
+}
+
+impl AddSubdiagnostic for ForbiddenLetReason {
+    fn add_to_diagnostic(self, diag: &mut Diagnostic) {
+        match self {
+            Self::GenericForbidden => {}
+            Self::NotSupportedOr(span) => {
+                diag.span_note(span, fluent::ast_passes::not_supported_or);
+            }
+            Self::NotSupportedParentheses(span) => {
+                diag.span_note(span, fluent::ast_passes::not_supported_parentheses);
+            },
+        }
+    }
+}