parse_meta: ditch parse_in_attr

Author: Centril

src/librustc_parse/config.rs

@@ -18,7 +18,6 @@ use syntax::ast::{self, Attribute, AttrItem, MetaItem};
 use syntax::edition::Edition;
 use syntax::mut_visit::*;
 use syntax::ptr::P;
-use syntax::tokenstream::DelimSpan;
 use syntax::sess::ParseSess;
 use syntax::util::map_in_place::MapInPlace;
 use syntax_pos::Span;
@@ -139,11 +138,10 @@ impl<'a> StripUnconfigured<'a> {
     }
 
     fn parse_cfg_attr(&self, attr: &Attribute) -> Option<(MetaItem, Vec<(AttrItem, Span)>)> {
-        match &attr.get_normal_item().args {
-            ast::MacArgs::Delimited(dspan, delim, tts) if !tts.is_empty() => {
-                if let ast::MacDelimiter::Brace | ast::MacDelimiter::Bracket = delim {
-                    self.error_malformed_cfg_attr_wrong_delim(*dspan);
-                }
+        match attr.get_normal_item().args {
+            ast::MacArgs::Delimited(dspan, delim, ref tts) if !tts.is_empty() => {
+                let msg = "wrong `cfg_attr` delimiters";
+                validate_attr::check_meta_bad_delim(self.sess, dspan, delim, msg);
                 match parse_in(self.sess, tts.clone(), "`cfg_attr` input", |p| p.parse_cfg_attr()) {
                     Ok(r) => return Some(r),
                     Err(mut e) => e
@@ -157,21 +155,6 @@ impl<'a> StripUnconfigured<'a> {
         None
     }
 
-    fn error_malformed_cfg_attr_wrong_delim(&self, dspan: DelimSpan) {
-        self.sess
-            .span_diagnostic
-            .struct_span_err(dspan.entire(), "wrong `cfg_attr` delimiters")
-            .multipart_suggestion(
-                "the delimiters should be `(` and `)`",
-                vec![
-                    (dspan.open, "(".to_string()),
-                    (dspan.close, ")".to_string()),
-                ],
-                Applicability::MachineApplicable,
-            )
-            .emit();
-    }
-
     fn error_malformed_cfg_attr_missing(&self, span: Span) {
         self.sess
             .span_diagnostic

src/librustc_parse/lib.rs

@@ -284,17 +284,6 @@ pub fn parse_in<'a, T>(
     Ok(result)
 }
 
-/// Runs the given subparser `f` on the tokens of the given `attr`'s item.
-fn parse_in_attr<'a, T>(
-    sess: &'a ParseSess,
-    attr: &ast::Attribute,
-    f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
-) -> PResult<'a, T> {
-    // FIXME(#66940, Centril | petrochenkov): refactor this function so it doesn't
-    // require reconstructing and immediately re-parsing delimiters.
-    parse_in(sess, attr.get_normal_item().args.outer_tokens(), "attribute", f)
-}
-
 // NOTE(Centril): The following probably shouldn't be here but it acknowledges the
 // fact that architecturally, we are using parsing (read on below to understand why).
 

src/librustc_parse/parser/attr.rs

@@ -220,7 +220,7 @@ impl<'a> Parser<'a> {
         Ok(attrs)
     }
 
-    pub(super) fn parse_unsuffixed_lit(&mut self) -> PResult<'a, ast::Lit> {
+    crate fn parse_unsuffixed_lit(&mut self) -> PResult<'a, ast::Lit> {
         let lit = self.parse_lit()?;
         debug!("checking if {:?} is unusuffixed", lit);
 
@@ -247,12 +247,27 @@ impl<'a> Parser<'a> {
             let lo = self.token.span;
             let item = self.parse_attr_item()?;
             expanded_attrs.push((item, lo.to(self.prev_span)));
-            self.eat(&token::Comma);
+            if !self.eat(&token::Comma) {
+                break;
+            }
         }
 
         Ok((cfg_predicate, expanded_attrs))
     }
 
+    /// Matches `COMMASEP(meta_item_inner)`.
+    crate fn parse_meta_seq_top(&mut self) -> PResult<'a, Vec<ast::NestedMetaItem>> {
+        // Presumably, the majority of the time there will only be one attr.
+        let mut nmis = Vec::with_capacity(1);
+        while self.token.kind != token::Eof {
+            nmis.push(self.parse_meta_item_inner()?);
+            if !self.eat(&token::Comma) {
+                break;
+            }
+        }
+        Ok(nmis)
+    }
+
     /// Matches the following grammar (per RFC 1559).
     ///
     ///     meta_item : PATH ( '=' UNSUFFIXED_LIT | '(' meta_item_inner? ')' )? ;

src/librustc_parse/validate_attr.rs

@@ -1,10 +1,13 @@
 //! Meta-syntax validation logic of attributes for post-expansion.
 
+use crate::parse_in;
+
 use rustc_errors::{PResult, Applicability};
 use rustc_feature::{AttributeTemplate, BUILTIN_ATTRIBUTE_MAP};
-use syntax::ast::{self, Attribute, AttrKind, Ident, MacArgs, MetaItem, MetaItemKind};
+use syntax::ast::{self, Attribute, AttrKind, Ident, MacArgs, MacDelimiter, MetaItem, MetaItemKind};
 use syntax::attr::mk_name_value_item_str;
 use syntax::early_buffered_lints::ILL_FORMED_ATTRIBUTE_INPUT;
+use syntax::tokenstream::DelimSpan;
 use syntax::sess::ParseSess;
 use syntax_pos::{Symbol, sym};
 
@@ -27,16 +30,45 @@ pub fn check_meta(sess: &ParseSess, attr: &Attribute) {
 pub fn parse_meta<'a>(sess: &'a ParseSess, attr: &Attribute) -> PResult<'a, MetaItem> {
     Ok(match attr.kind {
         AttrKind::Normal(ref item) => MetaItem {
-            path: item.path.clone(),
-            kind: super::parse_in_attr(sess, attr, |p| p.parse_meta_item_kind())?,
             span: attr.span,
+            path: item.path.clone(),
+            kind: match &attr.get_normal_item().args {
+                MacArgs::Empty => MetaItemKind::Word,
+                MacArgs::Eq(_, t) => {
+                    let v = parse_in(sess, t.clone(), "name value", |p| p.parse_unsuffixed_lit())?;
+                    MetaItemKind::NameValue(v)
+                }
+                MacArgs::Delimited(dspan, delim, t) => {
+                    check_meta_bad_delim(sess, *dspan, *delim, "wrong meta list delimiters");
+                    let nmis = parse_in(sess, t.clone(), "meta list", |p| p.parse_meta_seq_top())?;
+                    MetaItemKind::List(nmis)
+                }
+            }
         },
         AttrKind::DocComment(comment) => {
             mk_name_value_item_str(Ident::new(sym::doc, attr.span), comment, attr.span)
         }
     })
 }
 
+crate fn check_meta_bad_delim(sess: &ParseSess, span: DelimSpan, delim: MacDelimiter, msg: &str) {
+    if let ast::MacDelimiter::Parenthesis = delim {
+        return;
+    }
+
+    sess.span_diagnostic
+        .struct_span_err(span.entire(), msg)
+        .multipart_suggestion(
+            "the delimiters should be `(` and `)`",
+            vec![
+                (span.open, "(".to_string()),
+                (span.close, ")".to_string()),
+            ],
+            Applicability::MachineApplicable,
+        )
+        .emit();
+}
+
 /// Checks that the given meta-item is compatible with this `AttributeTemplate`.
 fn is_attr_template_compatible(template: &AttributeTemplate, meta: &ast::MetaItemKind) -> bool {
     match meta {

src/libsyntax_expand/proc_macro.rs

@@ -188,14 +188,14 @@ crate fn collect_derives(cx: &mut ExtCtxt<'_>, attrs: &mut Vec<ast::Attribute>)
             Some(x) => x,
         };
 
-        let mut retain_in_fm = true;
-        let mut retain_in_map = true;
+        let mut error_reported_filter_map = false;
+        let mut error_reported_map = false;
         let traits = nmis
             .into_iter()
             // 2) Moreover, let's ensure we have a path and not `#[derive("foo")]`.
             .filter_map(|nmi| match nmi {
                 NestedMetaItem::Literal(lit) => {
-                    retain_in_fm = false;
+                    error_reported_filter_map = true;
                     cx.struct_span_err(lit.span, "expected path to a trait, found literal")
                         .help("for example, write `#[derive(Debug)]` for `Debug`")
                         .emit();
@@ -209,7 +209,7 @@ crate fn collect_derives(cx: &mut ExtCtxt<'_>, attrs: &mut Vec<ast::Attribute>)
             // wanted this trait to be derived, so let's keep it.
             .map(|mi| {
                 let mut traits_dont_accept = |title, action| {
-                    retain_in_map = false;
+                    error_reported_map = true;
                     let sp = mi.span.with_lo(mi.path.span.hi());
                     cx.struct_span_err(sp, title)
                         .span_suggestion(
@@ -235,7 +235,7 @@ crate fn collect_derives(cx: &mut ExtCtxt<'_>, attrs: &mut Vec<ast::Attribute>)
             });
 
         result.extend(traits);
-        retain_in_fm && retain_in_map
+        !error_reported_filter_map && !error_reported_map
     });
     result
 }

src/test/ui/malformed/malformed-meta-delim.rs

@@ -0,0 +1,11 @@
+fn main() {}
+
+#[allow { foo_lint } ]
+//~^ ERROR wrong meta list delimiters
+//~| HELP the delimiters should be `(` and `)`
+fn delim_brace() {}
+
+#[allow [ foo_lint ] ]
+//~^ ERROR wrong meta list delimiters
+//~| HELP the delimiters should be `(` and `)`
+fn delim_bracket() {}

src/test/ui/malformed/malformed-meta-delim.stderr

@@ -0,0 +1,24 @@
+error: wrong meta list delimiters
+  --> $DIR/malformed-meta-delim.rs:3:9
+   |
+LL | #[allow { foo_lint } ]
+   |         ^^^^^^^^^^^^
+   |
+help: the delimiters should be `(` and `)`
+   |
+LL | #[allow ( foo_lint ) ]
+   |         ^          ^
+
+error: wrong meta list delimiters
+  --> $DIR/malformed-meta-delim.rs:8:9
+   |
+LL | #[allow [ foo_lint ] ]
+   |         ^^^^^^^^^^^^
+   |
+help: the delimiters should be `(` and `)`
+   |
+LL | #[allow ( foo_lint ) ]
+   |         ^          ^
+
+error: aborting due to 2 previous errors
+

src/test/ui/on-unimplemented/expected-comma-found-token.rs

@@ -6,7 +6,7 @@
 
 #[rustc_on_unimplemented(
     message="the message"
-    label="the label" //~ ERROR expected one of `)` or `,`, found `label`
+    label="the label" //~ ERROR expected `,`, found `label`
 )]
 trait T {}
 

src/test/ui/on-unimplemented/expected-comma-found-token.stderr

@@ -1,11 +1,8 @@
-error: expected one of `)` or `,`, found `label`
+error: expected `,`, found `label`
   --> $DIR/expected-comma-found-token.rs:9:5
    |
 LL |     message="the message"
-   |                          -
-   |                          |
-   |                          expected one of `)` or `,`
-   |                          help: missing `,`
+   |                          - expected `,`
 LL |     label="the label"
    |     ^^^^^ unexpected token