Auto merge of #64438 - cuviper:beta-rollup, r=Mark-Simulacrum

[beta] Rollup backports

Cherry-picked:

- Permit unwinding through FFI by default #62603
- pprust: Do not print spaces before some tokens #63897
- Account for doc comments coming from proc macros without spans #63930
- Support "soft" feature-gating using a lint #64066
- Update xLTO compatibility table in rustc book. #64092
- Include compiler-rt in the source tarball #64240
- Update LLVM submodule #64317

r? @Mark-Simulacrum

2 files changed, 25 insertions, 17 deletions

diff --git a/src/libsyntax/attr/builtin.rs b/src/libsyntax/attr/builtin.rs
index 5fb513783fb..b5037b75f79 100644
--- a/src/libsyntax/attr/builtin.rs
+++ b/src/libsyntax/attr/builtin.rs
@@ -154,23 +154,10 @@ pub struct Stability {
 #[derive(RustcEncodable, RustcDecodable, PartialEq, PartialOrd, Copy, Clone, Debug, Eq, Hash)]
 pub enum StabilityLevel {
     // Reason for the current stability level and the relevant rust-lang issue
-    Unstable { reason: Option<Symbol>, issue: u32 },
+    Unstable { reason: Option<Symbol>, issue: u32, is_soft: bool },
     Stable { since: Symbol },
 }
 
-impl Stability {
-    pub fn unstable(feature: Symbol, reason: Option<Symbol>, issue: u32) -> Stability {
-        Stability {
-            level: StabilityLevel::Unstable { reason, issue },
-            feature,
-            rustc_depr: None,
-            const_stability: None,
-            promotable: false,
-            allow_const_fn_ptr: false,
-        }
-    }
-}
-
 impl StabilityLevel {
     pub fn is_unstable(&self) -> bool {
         if let StabilityLevel::Unstable {..} = *self {
@@ -356,19 +343,27 @@ fn find_stability_generic<'a, I>(sess: &ParseSess,
                     let mut feature = None;
                     let mut reason = None;
                     let mut issue = None;
+                    let mut is_soft = false;
                     for meta in metas {
                         if let Some(mi) = meta.meta_item() {
                             match mi.name_or_empty() {
                                 sym::feature => if !get(mi, &mut feature) { continue 'outer },
                                 sym::reason => if !get(mi, &mut reason) { continue 'outer },
                                 sym::issue => if !get(mi, &mut issue) { continue 'outer },
+                                sym::soft => {
+                                    if !mi.is_word() {
+                                        let msg = "`soft` should not have any arguments";
+                                        sess.span_diagnostic.span_err(mi.span, msg);
+                                    }
+                                    is_soft = true;
+                                }
                                 _ => {
                                     handle_errors(
                                         sess,
                                         meta.span(),
                                         AttrError::UnknownMetaItem(
                                             mi.path.to_string(),
-                                            &["feature", "reason", "issue"]
+                                            &["feature", "reason", "issue", "soft"]
                                         ),
                                     );
                                     continue 'outer
@@ -400,7 +395,8 @@ fn find_stability_generic<'a, I>(sess: &ParseSess,
                                                       "incorrect 'issue'");
                                             continue
                                         }
-                                    }
+                                    },
+                                    is_soft,
                                 },
                                 feature,
                                 rustc_depr: None,
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index bda761244d5..536687bdbed 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -152,6 +152,18 @@ pub fn to_string<F>(f: F) -> String where
     printer.s.eof()
 }
 
+// This makes comma-separated lists look slightly nicer,
+// and also addresses a specific regression described in issue #63896.
+fn tt_prepend_space(tt: &TokenTree) -> bool {
+    match tt {
+        TokenTree::Token(token) => match token.kind {
+            token::Comma => false,
+            _ => true,
+        }
+        _ => true,
+    }
+}
+
 fn binop_to_string(op: BinOpToken) -> &'static str {
     match op {
         token::Plus     => "+",
@@ -684,7 +696,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target=pp::Printer> + std::ops::DerefM
 
     fn print_tts(&mut self, tts: tokenstream::TokenStream, convert_dollar_crate: bool) {
         for (i, tt) in tts.into_trees().enumerate() {
-            if i != 0 {
+            if i != 0 && tt_prepend_space(&tt) {
                 self.space();
             }
             self.print_tt(tt, convert_dollar_crate);