Improve should_emit & add parse_limited_all

Author: JonathanBrouwer

compiler/rustc_attr_parsing/src/context.rs

@@ -762,14 +762,31 @@ impl<'sess> AttributeParser<'sess, Early> {
         target_node_id: NodeId,
         features: Option<&'sess Features>,
     ) -> Option<Attribute> {
-        let mut p = Self {
-            features,
-            tools: Vec::new(),
-            parse_only: Some(sym),
+        let mut parsed = Self::parse_limited_all(
             sess,
-            stage: Early { emit_errors: ShouldEmit::Nothing },
-        };
-        let mut parsed = p.parse_attribute_list(
+            attrs,
+            Some(sym),
+            target_span,
+            target_node_id,
+            features,
+            ShouldEmit::Nothing,
+        );
+        assert!(parsed.len() <= 1);
+        parsed.pop()
+    }
+
+    pub fn parse_limited_all(
+        sess: &'sess Session,
+        attrs: &[ast::Attribute],
+        parse_only: Option<Symbol>,
+        target_span: Span,
+        target_node_id: NodeId,
+        features: Option<&'sess Features>,
+        emit_errors: ShouldEmit,
+    ) -> Vec<Attribute> {
+        let mut p =
+            Self { features, tools: Vec::new(), parse_only, sess, stage: Early { emit_errors } };
+        p.parse_attribute_list(
             attrs,
             target_span,
             target_node_id,
@@ -779,10 +796,7 @@ impl<'sess> AttributeParser<'sess, Early> {
             |_lint| {
                 panic!("can't emit lints here for now (nothing uses this atm)");
             },
-        );
-        assert!(parsed.len() <= 1);
-
-        parsed.pop()
+        )
     }
 
     pub fn parse_single<T>(