Auto merge of #61212 - alexcrichton:skip-rustc, r=pietroalbini

[rust.git] / src / libsyntax / config.rs

diff --git a/src/libsyntax/config.rs b/src/libsyntax/config.rs
index 18173628a2602f922cf89d8b0cb89ed675ffc295..fc413caa428dd748e8cf7610f10ac424034021fa 100644 (file)
--- a/src/libsyntax/config.rs
+++ b/src/libsyntax/config.rs
@@ -12,6 +12,7 @@
 use crate::mut_visit::*;
 use crate::parse::{token, ParseSess};
 use crate::ptr::P;
+use crate::symbol::sym;
 use crate::util::map_in_place::MapInPlace;
 
 use errors::Applicability;
@@ -90,9 +91,25 @@ pub fn process_cfg_attrs<T: HasAttrs>(&mut self, node: &mut T) {
     /// is in the original source file. Gives a compiler error if the syntax of
     /// the attribute is incorrect.
     fn process_cfg_attr(&mut self, attr: ast::Attribute) -> Vec<ast::Attribute> {
-        if !attr.check_name("cfg_attr") {
+        if !attr.check_name(sym::cfg_attr) {
             return vec![attr];
         }
+        if attr.tokens.len() == 0 {
+            self.sess.span_diagnostic
+                .struct_span_err(
+                    attr.span,
+                    "malformed `cfg_attr` attribute input",
+                ).span_suggestion(
+                    attr.span,
+                    "missing condition and attribute",
+                    "#[cfg_attr(condition, attribute, other_attribute, ...)]".to_owned(),
+                    Applicability::HasPlaceholders,
+                ).note("for more information, visit \
+                       <https://doc.rust-lang.org/reference/conditional-compilation.html\
+                       #the-cfg_attr-attribute>")
+                .emit();
+            return Vec::new();
+        }
 
         let (cfg_predicate, expanded_attrs) = match attr.parse(self.sess, |parser| {
             parser.expect(&token::OpenDelim(token::Paren))?;
@@ -205,7 +222,7 @@ fn visit_expr_attrs(&mut self, attrs: &[ast::Attribute]) {
     pub fn maybe_emit_expr_attr_err(&self, attr: &ast::Attribute) {
         if !self.features.map(|features| features.stmt_expr_attributes).unwrap_or(true) {
             let mut err = feature_err(self.sess,
-                                      "stmt_expr_attributes",
+                                      sym::stmt_expr_attributes,
                                       attr.span,
                                       GateIssue::Language,
                                       EXPLAIN_STMT_ATTR_SYNTAX);
@@ -285,9 +302,9 @@ pub fn configure_pat(&mut self, pat: &mut P<ast::Pat>) {
     /// See issue #51279.
     pub fn disallow_cfg_on_generic_param(&mut self, param: &ast::GenericParam) {
         for attr in param.attrs() {
-            let offending_attr = if attr.check_name("cfg") {
+            let offending_attr = if attr.check_name(sym::cfg) {
                 "cfg"
-            } else if attr.check_name("cfg_attr") {
+            } else if attr.check_name(sym::cfg_attr) {
                 "cfg_attr"
             } else {
                 continue;
@@ -350,5 +367,5 @@ fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
 }
 
 fn is_cfg(attr: &ast::Attribute) -> bool {
-    attr.check_name("cfg")
+    attr.check_name(sym::cfg)
 }