Migrate ast_lowering::lib and ast_lowering::item to SessionDiagnostic

compiler/rustc_ast_lowering/src/errors.rs

@@ -1,6 +1,6 @@
 use rustc_errors::{fluent, AddSubdiagnostic, Applicability, Diagnostic};
 use rustc_macros::SessionDiagnostic;
-use rustc_span::Span;
+use rustc_span::{Span, Symbol};
 
 #[derive(SessionDiagnostic, Clone, Copy)]
 #[error(ast_lowering::generic_type_with_parentheses, code = "E0214")]
@@ -27,3 +27,54 @@ impl AddSubdiagnostic for UseAngleBrackets {
         );
     }
 }
+
+#[derive(SessionDiagnostic)]
+#[help]
+#[error(ast_lowering::invalid_abi, code = "E0703")]
+pub struct InvalidAbi {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    pub abi: Symbol,
+    pub valid_abis: String,
+}
+
+#[derive(SessionDiagnostic, Clone, Copy)]
+#[error(ast_lowering::assoc_ty_parentheses)]
+pub struct AssocTyParentheses {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub sub: AssocTyParenthesesSub,
+}
+
+#[derive(Clone, Copy)]
+pub enum AssocTyParenthesesSub {
+    Empty { parentheses_span: Span },
+    NotEmpty { open_param: Span, close_param: Span },
+}
+
+impl AddSubdiagnostic for AssocTyParenthesesSub {
+    fn add_to_diagnostic(self, diag: &mut Diagnostic) {
+        match self {
+            Self::Empty { parentheses_span } => diag.multipart_suggestion(
+                fluent::ast_lowering::remove_parentheses,
+                vec![(parentheses_span, String::new())],
+                Applicability::MaybeIncorrect,
+            ),
+            Self::NotEmpty { open_param, close_param } => diag.multipart_suggestion(
+                fluent::ast_lowering::use_angle_brackets,
+                vec![(open_param, String::from("<")), (close_param, String::from(">"))],
+                Applicability::MaybeIncorrect,
+            ),
+        };
+    }
+}
+
+#[derive(SessionDiagnostic)]
+#[error(ast_lowering::misplaced_impl_trait, code = "E0562")]
+pub struct MisplacedImplTrait {
+    #[primary_span]
+    pub span: Span,
+    pub position: String,
+}