Implement boolean lit support in cfg predicates

Author: Urgau

compiler/rustc_ast/src/attr/mod.rs

@@ -527,6 +527,16 @@ impl NestedMetaItem {
 }
 }
 
+/// Returns the `MetaItem` if `self` is a `NestedMetaItem::MetaItem` or if it's
+/// `NestedMetaItem::Lit(MetaItemLit { kind: LitKind::Bool(_), .. })`.
+pubfnmeta_item_or_bool(&self) -> Option<&NestedMetaItem>{
+matchself{
+NestedMetaItem::MetaItem(_item) => Some(self),
+NestedMetaItem::Lit(MetaItemLit{kind:LitKind::Bool(_), .. }) => Some(self),
+ _ => None,
+}
+}
+
 /// Returns the `MetaItem` if `self` is a `NestedMetaItem::MetaItem`.
 pubfnmeta_item(&self) -> Option<&MetaItem>{
 matchself{

compiler/rustc_attr/src/builtin.rs

@@ -603,6 +603,7 @@ pub fn eval_condition(
 
 let cfg = match cfg {
  ast::NestedMetaItem::MetaItem(meta_item) => meta_item,
+ ast::NestedMetaItem::Lit(MetaItemLit{kind:LitKind::Bool(b), .. }) => return*b,
  _ => {
  dcx.emit_err(session_diagnostics::UnsupportedLiteral{
 span: cfg.span(),
@@ -649,7 +650,7 @@ pub fn eval_condition(
 }
  ast::MetaItemKind::List(mis) => {
 for mi in mis.iter(){
-if!mi.is_meta_item(){
+if mi.meta_item_or_bool().is_none(){
  dcx.emit_err(session_diagnostics::UnsupportedLiteral{
 span: mi.span(),
 reason:UnsupportedLiteralReason::Generic,

compiler/rustc_expand/src/config.rs

@@ -466,9 +466,9 @@ pub fn parse_cfg<'a>(meta_item: &'a MetaItem, sess: &Session) -> Option<&'a Nest
  sess.dcx().emit_err(InvalidCfg::MultiplePredicates{span: l.span()});
 None
 }
-Some([single]) => match single.is_meta_item(){
-true => Some(single),
-false => {
+Some([single]) => match single.meta_item_or_bool(){
+Some(meta_item) => Some(meta_item),
+None => {
  sess.dcx().emit_err(InvalidCfg::PredicateLiteral{span: single.span()});
 None
 }

compiler/rustc_metadata/src/native_libs.rs

@@ -309,7 +309,7 @@ impl<'tcx> Collector<'tcx> {
 .emit_err(errors::LinkCfgSinglePredicate{span: item.span()});
 continue;
 };
-if !link_cfg.is_meta_item(){
+letSome(link_cfg) = link_cfg.meta_item_or_bool()else{
  sess.dcx()
 .emit_err(errors::LinkCfgSinglePredicate{span: item.span()});
 continue;

compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs

@@ -413,7 +413,9 @@ impl<'tcx> OnUnimplementedDirective {
 }else{
 let cond = item_iter
 .next()
-.ok_or_else(|| tcx.dcx().emit_err(EmptyOnClauseInOnUnimplemented{ span }))?;
+.ok_or_else(|| tcx.dcx().emit_err(EmptyOnClauseInOnUnimplemented{ span }))?
+.meta_item_or_bool()
+.ok_or_else(|| tcx.dcx().emit_err(InvalidOnClauseInOnUnimplemented{ span }))?;
  attr::eval_condition(cond,&tcx.sess,Some(tcx.features()),&mut |cfg| {
 ifletSome(value) = cfg.value
  && letErr(guar) = parse_value(value, cfg.span)

tests/ui/cfg/true-false.rs

@@ -0,0 +1,29 @@
+//@ run-pass
+
+#![feature(link_cfg)]
+
+#[cfg(true)]
+fnfoo() -> bool{
+cfg!(true)
+}
+
+#[cfg(false)]
+fnfoo() -> bool{
+cfg!(false)
+}
+
+#[cfg_attr(true, cfg(false))]
+fnfoo(){}
+
+#[link(name = "foo", cfg(false))]
+extern"C"{}
+
+fnmain(){
+assert!(foo());
+assert!(cfg!(true));
+assert!(!cfg!(false));
+assert!(cfg!(not(false)));
+assert!(cfg!(all(true)));
+assert!(cfg!(any(true)));
+assert!(!cfg!(not(true)));
+}