Rollup of 6 pull requests

src/libcore/lib.rs

@@ -44,7 +44,7 @@
 // Here we explicitly #[cfg]-out this whole crate when testing. If we don't do
 // this, both the generated test artifact and the linked libtest (which
 // transitively includes libcore) will both define the same set of lang items,
-// and this will cause the E0152 "duplicate lang item found" error. See
+// and this will cause the E0152 "found duplicate lang item" error. See
 // discussion in #50466 for details.
 //
 // This cfg won't affect doc tests.

src/librustc/middle/lang_items.rs

@@ -184,7 +184,7 @@ impl LanguageItemCollector<'tcx> {
                         self.tcx.sess,
                         span,
                         E0152,
-                        "duplicate lang item found: `{}`.",
+                        "found duplicate lang item `{}`",
                         name
                     ),
                     None => {
@@ -206,12 +206,12 @@ impl LanguageItemCollector<'tcx> {
                     },
                 };
                 if let Some(span) = self.tcx.hir().span_if_local(original_def_id) {
-                    err.span_note(span, "first defined here.");
+                    err.span_note(span, "first defined here");
                 } else {
                     match self.tcx.extern_crate(original_def_id) {
                         Some(ExternCrate {dependency_of, ..}) => {
                             err.note(&format!(
-                            "first defined in crate `{}` (which `{}` depends on).",
+                            "first defined in crate `{}` (which `{}` depends on)",
                                       self.tcx.crate_name(original_def_id.krate),
                                       self.tcx.crate_name(*dependency_of)));
                         },

src/librustc/traits/error_reporting.rs

@@ -1156,7 +1156,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 err.span_help(impl_span, "trait impl with same name found");
                 let trait_crate = self.tcx.crate_name(trait_with_same_path.krate);
                 let crate_msg = format!(
-                    "Perhaps two different versions of crate `{}` are being used?",
+                    "perhaps two different versions of crate `{}` are being used?",
                     trait_crate
                 );
                 err.note(&crate_msg);

src/librustc_ast_passes/feature_gate.rs

@@ -413,7 +413,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 self.check_extern(bare_fn_ty.ext);
             }
             ast::TyKind::Never => {
-                gate_feature_post!(&self, never_type, ty.span, "The `!` type is experimental");
+                gate_feature_post!(&self, never_type, ty.span, "the `!` type is experimental");
             }
             _ => {}
         }

src/librustc_builtin_macros/test.rs

@@ -325,7 +325,7 @@ fn should_panic(cx: &ExtCtxt<'_>, i: &ast::Item) -> ShouldPanic {
                              `expected = \"error message\"`",
                         )
                         .note(
-                            "Errors in this attribute were erroneously \
+                            "errors in this attribute were erroneously \
                                 allowed and will become a hard error in a \
                                 future release.",
                         )

src/librustc_lint/builtin.rs

@@ -657,7 +657,7 @@ impl EarlyLintPass for AnonymousParameters {
                                 )
                                 .span_suggestion(
                                     arg.pat.span,
-                                    "Try naming the parameter or explicitly \
+                                    "try naming the parameter or explicitly \
                                     ignoring it",
                                     format!("_: {}", ty_snip),
                                     appl,
@@ -1934,21 +1934,21 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
             use rustc::ty::TyKind::*;
             match ty.kind {
                 // Primitive types that don't like 0 as a value.
-                Ref(..) => Some((format!("References must be non-null"), None)),
+                Ref(..) => Some((format!("references must be non-null"), None)),
                 Adt(..) if ty.is_box() => Some((format!("`Box` must be non-null"), None)),
-                FnPtr(..) => Some((format!("Function pointers must be non-null"), None)),
-                Never => Some((format!("The never type (`!`) has no valid value"), None)),
+                FnPtr(..) => Some((format!("function pointers must be non-null"), None)),
+                Never => Some((format!("the `!` type has no valid value"), None)),
                 RawPtr(tm) if matches!(tm.ty.kind, Dynamic(..)) =>
                 // raw ptr to dyn Trait
                 {
-                    Some((format!("The vtable of a wide raw pointer must be non-null"), None))
+                    Some((format!("the vtable of a wide raw pointer must be non-null"), None))
                 }
                 // Primitive types with other constraints.
                 Bool if init == InitKind::Uninit => {
-                    Some((format!("Booleans must be `true` or `false`"), None))
+                    Some((format!("booleans must be either `true` or `false`"), None))
                 }
                 Char if init == InitKind::Uninit => {
-                    Some((format!("Characters must be a valid unicode codepoint"), None))
+                    Some((format!("characters must be a valid Unicode codepoint"), None))
                 }
                 // Recurse and checks for some compound types.
                 Adt(adt_def, substs) if !adt_def.is_union() => {
@@ -1959,21 +1959,24 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidValue {
                         // return `Bound::Excluded`.  (And we have tests checking that we
                         // handle the attribute correctly.)
                         (Bound::Included(lo), _) if lo > 0 => {
-                            return Some((format!("{} must be non-null", ty), None));
+                            return Some((format!("`{}` must be non-null", ty), None));
                         }
                         (Bound::Included(_), _) | (_, Bound::Included(_))
                             if init == InitKind::Uninit =>
                         {
                             return Some((
-                                format!("{} must be initialized inside its custom valid range", ty),
+                                format!(
+                                    "`{}` must be initialized inside its custom valid range",
+                                    ty,
+                                ),
                                 None,
                             ));
                         }
                         _ => {}
                     }
                     // Now, recurse.
                     match adt_def.variants.len() {
-                        0 => Some((format!("0-variant enums have no valid value"), None)),
+                        0 => Some((format!("enums with no variants have no valid value"), None)),
                         1 => {
                             // Struct, or enum with exactly one variant.
                             // Proceed recursively, check all fields.

src/librustc_mir/borrow_check/nll.rs

@@ -360,7 +360,7 @@ pub(super) fn dump_annotation<'a, 'tcx>(
     // better.
 
     if let Some(closure_region_requirements) = closure_region_requirements {
-        let mut err = tcx.sess.diagnostic().span_note_diag(body.span, "External requirements");
+        let mut err = tcx.sess.diagnostic().span_note_diag(body.span, "external requirements");
 
         regioncx.annotate(tcx, &mut err);
 
@@ -379,7 +379,7 @@ pub(super) fn dump_annotation<'a, 'tcx>(
 
         err.buffer(errors_buffer);
     } else {
-        let mut err = tcx.sess.diagnostic().span_note_diag(body.span, "No external requirements");
+        let mut err = tcx.sess.diagnostic().span_note_diag(body.span, "no external requirements");
         regioncx.annotate(tcx, &mut err);
 
         err.buffer(errors_buffer);

src/librustc_mir/dataflow/mod.rs

@@ -668,6 +668,26 @@ pub trait BottomValue {
     const BOTTOM_VALUE: bool;
 
     /// Merges `in_set` into `inout_set`, returning `true` if `inout_set` changed.
+    ///
+    /// It is almost certainly wrong to override this, since it automatically applies
+    /// * `inout_set & in_set` if `BOTTOM_VALUE == true`
+    /// * `inout_set | in_set` if `BOTTOM_VALUE == false`
+    ///
+    /// This means that if a bit is not `BOTTOM_VALUE`, it is propagated into all target blocks.
+    /// For clarity, the above statement again from a different perspective:
+    /// A bit in the block's entry set is `!BOTTOM_VALUE` if *any* predecessor block's bit value is
+    /// `!BOTTOM_VALUE`.
+    ///
+    /// There are situations where you want the opposite behaviour: propagate only if *all*
+    /// predecessor blocks's value is `!BOTTOM_VALUE`.
+    /// E.g. if you want to know whether a bit is *definitely* set at a specific location. This
+    /// means that all code paths leading to the location must have set the bit, instead of any
+    /// code path leading there.
+    ///
+    /// If you want this kind of "definitely set" analysis, you need to
+    /// 1. Invert `BOTTOM_VALUE`
+    /// 2. Reset the `entry_set` in `start_block_effect` to `!BOTTOM_VALUE`
+    /// 3. Override `join` to do the opposite from what it's doing now.
     #[inline]
     fn join<T: Idx>(&self, inout_set: &mut BitSet<T>, in_set: &BitSet<T>) -> bool {
         if Self::BOTTOM_VALUE == false {
@@ -685,7 +705,9 @@ pub trait BottomValue {
 /// for each block individually. The entry set for all other basic blocks is
 /// initialized to `Self::BOTTOM_VALUE`. The dataflow analysis then
 /// iteratively modifies the various entry sets (but leaves the the transfer
-/// function unchanged).
+/// function unchanged). `BottomValue::join` is used to merge the bitsets from
+/// two blocks (e.g. when two blocks' terminator jumps to a single block, that
+/// target block's state is the merged state of both incoming blocks).
 pub trait BitDenotation<'tcx>: BottomValue {
     /// Specifies what index type is used to access the bitvector.
     type Idx: Idx;

src/librustc_mir/transform/const_prop.rs

@@ -74,6 +74,31 @@ impl<'tcx> MirPass<'tcx> for ConstProp {
             return;
         }
 
+        // Check if it's even possible to satisfy the 'where' clauses
+        // for this item.
+        // This branch will never be taken for any normal function.
+        // However, it's possible to `#!feature(trivial_bounds)]` to write
+        // a function with impossible to satisfy clauses, e.g.:
+        // `fn foo() where String: Copy {}`
+        //
+        // We don't usually need to worry about this kind of case,
+        // since we would get a compilation error if the user tried
+        // to call it. However, since we can do const propagation
+        // even without any calls to the function, we need to make
+        // sure that it even makes sense to try to evaluate the body.
+        // If there are unsatisfiable where clauses, then all bets are
+        // off, and we just give up.
+        if !tcx.substitute_normalize_and_test_predicates((
+            source.def_id(),
+            InternalSubsts::identity_for_item(tcx, source.def_id()),
+        )) {
+            trace!(
+                "ConstProp skipped for item with unsatisfiable predicates: {:?}",
+                source.def_id()
+            );
+            return;
+        }
+
         trace!("ConstProp starting for {:?}", source.def_id());
 
         let dummy_body = &Body::new(

src/librustc_parse/parser/attr.rs

@@ -236,8 +236,8 @@ impl<'a> Parser<'a> {
             self.struct_span_err(lit.span, msg)
                 .help(
                     "instead of using a suffixed literal \
-                                    (1u8, 1.0f32, etc.), use an unsuffixed version \
-                                    (1, 1.0, etc.).",
+                                    (`1u8`, `1.0f32`, etc.), use an unsuffixed version \
+                                    (`1`, `1.0`, etc.)",
                 )
                 .emit()
         }

src/librustc_parse/parser/mod.rs

@@ -2,6 +2,7 @@ pub mod attr;
 mod expr;
 mod item;
 mod module;
+pub use module::{ModulePath, ModulePathSuccess};
 mod pat;
 mod path;
 mod ty;
@@ -117,7 +118,8 @@ pub struct Parser<'a> {
     /// Used to determine the path to externally loaded source files.
     pub(super) directory: Directory<'a>,
     /// `true` to parse sub-modules in other files.
-    pub(super) recurse_into_file_modules: bool,
+    // Public for rustfmt usage.
+    pub recurse_into_file_modules: bool,
     /// Name of the root module this parser originated from. If `None`, then the
     /// name is not known. This does not change while the parser is descending
     /// into modules, and sub-parsers have new values for this name.
@@ -126,7 +128,8 @@ pub struct Parser<'a> {
     token_cursor: TokenCursor,
     desugar_doc_comments: bool,
     /// `true` we should configure out of line modules as we parse.
-    cfg_mods: bool,
+    // Public for rustfmt usage.
+    pub cfg_mods: bool,
     /// This field is used to keep track of how many left angle brackets we have seen. This is
     /// required in order to detect extra leading left angle brackets (`<` characters) and error
     /// appropriately.
@@ -483,7 +486,8 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
+    // Public for rustfmt usage.
+    pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
         self.parse_ident_common(true)
     }
 
@@ -540,7 +544,8 @@ impl<'a> Parser<'a> {
 
     /// If the next token is the given keyword, eats it and returns `true`.
     /// Otherwise, returns `false`. An expectation is also added for diagnostics purposes.
-    fn eat_keyword(&mut self, kw: Symbol) -> bool {
+    // Public for rustfmt usage.
+    pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
         if self.check_keyword(kw) {
             self.bump();
             true

src/librustc_parse/parser/module.rs

@@ -14,13 +14,15 @@ use syntax::token::{self, TokenKind};
 use std::path::{self, Path, PathBuf};
 
 /// Information about the path to a module.
-pub(super) struct ModulePath {
+// Public for rustfmt usage.
+pub struct ModulePath {
     name: String,
     path_exists: bool,
     pub result: Result<ModulePathSuccess, Error>,
 }
 
-pub(super) struct ModulePathSuccess {
+// Public for rustfmt usage.
+pub struct ModulePathSuccess {
     pub path: PathBuf,
     pub directory_ownership: DirectoryOwnership,
 }
@@ -177,7 +179,8 @@ impl<'a> Parser<'a> {
         }
     }
 
-    pub(super) fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
+    // Public for rustfmt usage.
+    pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
         if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
             let s = s.as_str();
 
@@ -194,7 +197,8 @@ impl<'a> Parser<'a> {
     }
 
     /// Returns a path to a module.
-    pub(super) fn default_submod_path(
+    // Public for rustfmt usage.
+    pub fn default_submod_path(
         id: ast::Ident,
         relative: Option<ast::Ident>,
         dir_path: &Path,

src/librustc_parse/parser/pat.rs

@@ -209,13 +209,13 @@ impl<'a> Parser<'a> {
         if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
             err.span_suggestion(
                 seq_span,
-                "try adding parentheses to match on a tuple..",
+                "try adding parentheses to match on a tuple...",
                 format!("({})", seq_snippet),
                 Applicability::MachineApplicable,
             )
             .span_suggestion(
                 seq_span,
-                "..or a vertical bar to match on multiple alternatives",
+                "...or a vertical bar to match on multiple alternatives",
                 format!("{}", seq_snippet.replace(",", " |")),
                 Applicability::MachineApplicable,
             );

src/librustc_passes/diagnostic_items.rs

@@ -73,7 +73,7 @@ fn collect_item(
                 )),
             };
             if let Some(span) = tcx.hir().span_if_local(original_def_id) {
-                err.span_note(span, "first defined here.");
+                err.span_note(span, "first defined here");
             } else {
                 err.note(&format!(
                     "first defined in crate `{}`.",

src/librustc_resolve/build_reduced_graph.rs

@@ -963,7 +963,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                             .session
                             .struct_span_err(
                                 attr.span,
-                                "`macro_use` is not supported on `extern crate self`",
+                                "`#[macro_use]` is not supported on `extern crate self`",
                             )
                             .emit();
                     }
@@ -1054,10 +1054,10 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
     fn contains_macro_use(&mut self, attrs: &[ast::Attribute]) -> bool {
         for attr in attrs {
             if attr.check_name(sym::macro_escape) {
-                let msg = "macro_escape is a deprecated synonym for macro_use";
+                let msg = "`#[macro_escape]` is a deprecated synonym for `#[macro_use]`";
                 let mut err = self.r.session.struct_span_warn(attr.span, msg);
                 if let ast::AttrStyle::Inner = attr.style {
-                    err.help("consider an outer attribute, `#[macro_use]` mod ...").emit();
+                    err.help("try an outer attribute: `#[macro_use]`").emit();
                 } else {
                     err.emit();
                 }
@@ -1066,7 +1066,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
             }
 
             if !attr.is_word() {
-                self.r.session.span_err(attr.span, "arguments to macro_use are not allowed here");
+                self.r.session.span_err(attr.span, "arguments to `macro_use` are not allowed here");
             }
             return true;
         }

src/librustc_resolve/lib.rs

@@ -2006,7 +2006,7 @@ impl<'a> Resolver<'a> {
                             continue;
                         }
                     }
-                    let msg = "there are too many initial `super`s.".to_string();
+                    let msg = "there are too many leading `super` keywords".to_string();
                     return PathResult::Failed {
                         span: ident.span,
                         label: msg,

src/librustc_typeck/check/cast.rs

@@ -381,7 +381,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                     if unknown_cast_to { "to" } else { "from" }
                 );
                 err.note(
-                    "The type information given here is insufficient to check whether \
+                    "the type information given here is insufficient to check whether \
                           the pointer cast is valid",
                 );
                 if unknown_cast_to {

src/librustc_typeck/check/method/suggest.rs

@@ -479,7 +479,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     macro_rules! report_function {
                         ($span:expr, $name:expr) => {
                             err.note(&format!(
-                                "{} is a function, perhaps you wish to call it",
+                                "`{}` is a function, perhaps you wish to call it",
                                 $name
                             ));
                         };