Rollup merge of #95189 - fmease:fix-issue-94340, r=estebank

Stop flagging unexpected inner attributes as outer ones in certain diagnostics

Fixes #94340.

In the issue to-be-fixed I write that the general message _an inner attribute is not permitted in this context_ should be more specific noting that the “context” is the `include` macro. This, however, cannot be achieved without touching a lot of things and passing a flag to the `parse_expr` and `parse_item` calls in `expand_include`. This seems rather hacky to me. That's why I left it as it. `Span::from_expansion` does not apply either AFAIK.

`@rustbot` label A-diagnostics T-compiler

Author: Dylan-DPC

compiler/rustc_builtin_macros/src/source_util.rs

@@ -141,17 +141,20 @@ pub fn expand_include<'cx>(
 
         fn make_items(mut self: Box<ExpandResult<'a>>) -> Option<SmallVec<[P<ast::Item>; 1]>> {
             let mut ret = SmallVec::new();
-            while self.p.token != token::Eof {
+            loop {
                 match self.p.parse_item(ForceCollect::No) {
                     Err(mut err) => {
                         err.emit();
                         break;
                     }
                     Ok(Some(item)) => ret.push(item),
                     Ok(None) => {
-                        let token = pprust::token_to_string(&self.p.token);
-                        let msg = format!("expected item, found `{}`", token);
-                        self.p.struct_span_err(self.p.token.span, &msg).emit();
+                        if self.p.token != token::Eof {
+                            let token = pprust::token_to_string(&self.p.token);
+                            let msg = format!("expected item, found `{}`", token);
+                            self.p.struct_span_err(self.p.token.span, &msg).emit();
+                        }
+
                         break;
                     }
                 }

compiler/rustc_parse/src/parser/attr.rs

@@ -13,7 +13,7 @@ use tracing::debug;
 #[derive(Debug)]
 pub enum InnerAttrPolicy<'a> {
     Permitted,
-    Forbidden { reason: &'a str, saw_doc_comment: bool, prev_attr_sp: Option<Span> },
+    Forbidden { reason: &'a str, saw_doc_comment: bool, prev_outer_attr_sp: Option<Span> },
 }
 
 const DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG: &str = "an inner attribute is not \
@@ -22,7 +22,7 @@ const DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG: &str = "an inner attribute is not \
 pub(super) const DEFAULT_INNER_ATTR_FORBIDDEN: InnerAttrPolicy<'_> = InnerAttrPolicy::Forbidden {
     reason: DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG,
     saw_doc_comment: false,
-    prev_attr_sp: None,
+    prev_outer_attr_sp: None,
 };
 
 enum OuterAttributeType {
@@ -34,22 +34,24 @@ enum OuterAttributeType {
 impl<'a> Parser<'a> {
     /// Parses attributes that appear before an item.
     pub(super) fn parse_outer_attributes(&mut self) -> PResult<'a, AttrWrapper> {
-        let mut attrs: Vec<ast::Attribute> = Vec::new();
+        let mut outer_attrs: Vec<ast::Attribute> = Vec::new();
         let mut just_parsed_doc_comment = false;
         let start_pos = self.token_cursor.num_next_calls;
         loop {
             let attr = if self.check(&token::Pound) {
+                let prev_outer_attr_sp = outer_attrs.last().map(|attr| attr.span);
+
                 let inner_error_reason = if just_parsed_doc_comment {
                     "an inner attribute is not permitted following an outer doc comment"
-                } else if !attrs.is_empty() {
+                } else if prev_outer_attr_sp.is_some() {
                     "an inner attribute is not permitted following an outer attribute"
                 } else {
                     DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG
                 };
                 let inner_parse_policy = InnerAttrPolicy::Forbidden {
                     reason: inner_error_reason,
                     saw_doc_comment: just_parsed_doc_comment,
-                    prev_attr_sp: attrs.last().map(|a| a.span),
+                    prev_outer_attr_sp,
                 };
                 just_parsed_doc_comment = false;
                 Some(self.parse_attribute(inner_parse_policy)?)
@@ -97,12 +99,14 @@ impl<'a> Parser<'a> {
             };
 
             if let Some(attr) = attr {
-                attrs.push(attr);
+                if attr.style == ast::AttrStyle::Outer {
+                    outer_attrs.push(attr);
+                }
             } else {
                 break;
             }
         }
-        Ok(AttrWrapper::new(attrs.into(), start_pos))
+        Ok(AttrWrapper::new(outer_attrs.into(), start_pos))
     }
 
     /// Matches `attribute = # ! [ meta_item ]`.
@@ -215,15 +219,15 @@ impl<'a> Parser<'a> {
     }
 
     pub(super) fn error_on_forbidden_inner_attr(&self, attr_sp: Span, policy: InnerAttrPolicy<'_>) {
-        if let InnerAttrPolicy::Forbidden { reason, saw_doc_comment, prev_attr_sp } = policy {
-            let prev_attr_note =
+        if let InnerAttrPolicy::Forbidden { reason, saw_doc_comment, prev_outer_attr_sp } = policy {
+            let prev_outer_attr_note =
                 if saw_doc_comment { "previous doc comment" } else { "previous outer attribute" };
 
             let mut diag = self.struct_span_err(attr_sp, reason);
 
-            if let Some(prev_attr_sp) = prev_attr_sp {
+            if let Some(prev_outer_attr_sp) = prev_outer_attr_sp {
                 diag.span_label(attr_sp, "not permitted following an outer attribute")
-                    .span_label(prev_attr_sp, prev_attr_note);
+                    .span_label(prev_outer_attr_sp, prev_outer_attr_note);
             }
 
             diag.note(

src/test/ui/parser/attr.rs

@@ -3,5 +3,4 @@
 fn main() {}
 
 #![lang = "foo"] //~ ERROR an inner attribute is not permitted in this context
-                 //~| ERROR definition of an unknown language item: `foo`
 fn foo() {}

src/test/ui/parser/attr.stderr

@@ -3,7 +3,6 @@ error: an inner attribute is not permitted in this context
    |
 LL | #![lang = "foo"]
    | ^^^^^^^^^^^^^^^^
-LL |
 LL | fn foo() {}
    | ----------- the inner attribute doesn't annotate this function
    |
@@ -14,12 +13,5 @@ LL - #![lang = "foo"]
 LL + #[lang = "foo"]
    | 
 
-error[E0522]: definition of an unknown language item: `foo`
-  --> $DIR/attr.rs:5:1
-   |
-LL | #![lang = "foo"]
-   | ^^^^^^^^^^^^^^^^ definition of unknown language item `foo`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0522`.

src/test/ui/parser/issues/auxiliary/issue-94340-inc.rs

@@ -0,0 +1,3 @@
+// include file for issue-94340.rs
+#![deny(rust_2018_idioms)]
+#![deny(unused_must_use)]

src/test/ui/parser/issues/issue-94340.rs

@@ -0,0 +1,8 @@
+// Make sure that unexpected inner attributes are not labeled as outer ones in diagnostics when
+// trying to parse an item and that they are subsequently ignored not triggering confusing extra
+// diagnostics like "expected item after attributes" which is not true for `include!` which can
+// include empty files.
+
+include!("auxiliary/issue-94340-inc.rs");
+
+fn main() {}

src/test/ui/parser/issues/issue-94340.stderr

@@ -0,0 +1,20 @@
+error: an inner attribute is not permitted in this context
+  --> $DIR/auxiliary/issue-94340-inc.rs:2:1
+   |
+LL | #![deny(rust_2018_idioms)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files
+   = note: outer attributes, like `#[test]`, annotate the item following them
+
+error: an inner attribute is not permitted in this context
+  --> $DIR/auxiliary/issue-94340-inc.rs:3:1
+   |
+LL | #![deny(unused_must_use)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files
+   = note: outer attributes, like `#[test]`, annotate the item following them
+
+error: aborting due to 2 previous errors
+