Rollup merge of #58762 - petrochenkov:unwind, r=Mark-Simulacrum

Mention `unwind(aborts)` in diagnostics for `#[unwind]`

Simplify input validation for `#[unwind]`, add tests

cc https://github.com/rust-lang/rust/issues/58760
r? @Mark-Simulacrum

src/librustc_mir/build/mod.rs

@@ -579,6 +579,10 @@ fn should_abort_on_panic<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
     // Not callable from C, so we can safely unwind through these
     if abi == Abi::Rust || abi == Abi::RustCall { return false; }
 
+    // Validate `#[unwind]` syntax regardless of platform-specific panic strategy
+    let attrs = &tcx.get_attrs(fn_def_id);
+    let unwind_attr = attr::find_unwind_attr(Some(tcx.sess.diagnostic()), attrs);
+
     // We never unwind, so it's not relevant to stop an unwind
     if tcx.sess.panic_strategy() != PanicStrategy::Unwind { return false; }
 
@@ -587,8 +591,7 @@ fn should_abort_on_panic<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
 
     // This is a special case: some functions have a C abi but are meant to
     // unwind anyway. Don't stop them.
-    let attrs = &tcx.get_attrs(fn_def_id);
-    match attr::find_unwind_attr(Some(tcx.sess.diagnostic()), attrs) {
+    match unwind_attr {
         None => true,
         Some(UnwindAttr::Allowed) => false,
         Some(UnwindAttr::Aborts) => true,

src/libsyntax/attr/builtin.rs

@@ -7,7 +7,7 @@ use crate::parse::ParseSess;
 use errors::{Applicability, Handler};
 use syntax_pos::{symbol::Symbol, Span};
 
-use super::{list_contains_name, mark_used, MetaItemKind};
+use super::{mark_used, MetaItemKind};
 
 enum AttrError {
     MultipleItem(Name),
@@ -79,40 +79,26 @@ pub enum UnwindAttr {
 
 /// Determine what `#[unwind]` attribute is present in `attrs`, if any.
 pub fn find_unwind_attr(diagnostic: Option<&Handler>, attrs: &[Attribute]) -> Option<UnwindAttr> {
-    let syntax_error = |attr: &Attribute| {
-        mark_used(attr);
-        diagnostic.map(|d| {
-            span_err!(d, attr.span, E0633, "malformed `#[unwind]` attribute");
-        });
-        None
-    };
-
     attrs.iter().fold(None, |ia, attr| {
-        if attr.path != "unwind" {
-            return ia;
-        }
-        let meta = match attr.meta() {
-            Some(meta) => meta.node,
-            None => return ia,
-        };
-        match meta {
-            MetaItemKind::Word => {
-                syntax_error(attr)
-            }
-            MetaItemKind::List(ref items) => {
-                mark_used(attr);
-                if items.len() != 1 {
-                    syntax_error(attr)
-                } else if list_contains_name(&items[..], "allowed") {
-                    Some(UnwindAttr::Allowed)
-                } else if list_contains_name(&items[..], "aborts") {
-                    Some(UnwindAttr::Aborts)
-                } else {
-                    syntax_error(attr)
+        if attr.check_name("unwind") {
+            if let Some(meta) = attr.meta() {
+                if let MetaItemKind::List(items) = meta.node {
+                    if items.len() == 1 {
+                        if items[0].check_name("allowed") {
+                            return Some(UnwindAttr::Allowed);
+                        } else if items[0].check_name("aborts") {
+                            return Some(UnwindAttr::Aborts);
+                        }
+                    }
+
+                    diagnostic.map(|d| {
+                        span_err!(d, attr.span, E0633, "malformed `#[unwind]` attribute");
+                    });
                 }
             }
-            _ => ia,
         }
+
+        ia
     })
 }
 

src/libsyntax/feature_gate.rs

@@ -1176,7 +1176,7 @@ pub const BUILTIN_ATTRIBUTES: &[(&str, AttributeType, AttributeTemplate, Attribu
            "dropck_eyepatch",
            "may_dangle has unstable semantics and may be removed in the future",
            cfg_fn!(dropck_eyepatch))),
-    ("unwind", Whitelisted, template!(List: "allowed"), Gated(Stability::Unstable,
+    ("unwind", Whitelisted, template!(List: "allowed|aborts"), Gated(Stability::Unstable,
                                   "unwind_attributes",
                                   "#[unwind] is experimental",
                                   cfg_fn!(unwind_attributes))),

src/test/ui/malformed/malformed-unwind-1.rs

@@ -0,0 +1,11 @@
+#![feature(unwind_attributes)]
+
+#[unwind]
+//~^ ERROR attribute must be of the form
+extern "C" fn f1() {}
+
+#[unwind = ""]
+//~^ ERROR attribute must be of the form
+extern "C" fn f2() {}
+
+fn main() {}

src/test/ui/malformed/malformed-unwind-1.stderr

@@ -0,0 +1,14 @@
+error: attribute must be of the form `#[unwind(allowed|aborts)]`
+  --> $DIR/malformed-unwind-1.rs:3:1
+   |
+LL | #[unwind]
+   | ^^^^^^^^^
+
+error: attribute must be of the form `#[unwind(allowed|aborts)]`
+  --> $DIR/malformed-unwind-1.rs:7:1
+   |
+LL | #[unwind = ""]
+   | ^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+

src/test/ui/malformed/malformed-unwind-2.rs

@@ -0,0 +1,11 @@
+#![feature(unwind_attributes)]
+
+#[unwind(allowed, aborts)]
+//~^ ERROR malformed `#[unwind]` attribute
+extern "C" fn f1() {}
+
+#[unwind(unsupported)]
+//~^ ERROR malformed `#[unwind]` attribute
+extern "C" fn f2() {}
+
+fn main() {}

src/test/ui/malformed/malformed-unwind-2.stderr

@@ -0,0 +1,15 @@
+error[E0633]: malformed `#[unwind]` attribute
+  --> $DIR/malformed-unwind-2.rs:3:1
+   |
+LL | #[unwind(allowed, aborts)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0633]: malformed `#[unwind]` attribute
+  --> $DIR/malformed-unwind-2.rs:7:1
+   |
+LL | #[unwind(unsupported)]
+   | ^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0633`.