Rollup of 5 pull requests

src/librustc_ast/ast.rs

@@ -25,6 +25,7 @@ pub use UnsafeSource::*;
 use crate::ptr::P;
 use crate::token::{self, DelimToken};
 use crate::tokenstream::{DelimSpan, TokenStream, TokenTree};
+use crate::visit::{walk_ty, Visitor};
 
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::Lrc;
@@ -1795,6 +1796,26 @@ pub struct Ty {
     pub span: Span,
 }
 
+impl Ty {
+    /// Returns `true` if the kind of this type or any types contained within are `impl Trait`.
+    pub fn contains_impl_trait(&self) -> bool {
+        struct ContainsImplTrait(bool);
+
+        impl<'ast> Visitor<'ast> for ContainsImplTrait {
+            fn visit_ty(&mut self, t: &'ast Ty) {
+                self.0 |= matches!(t.kind, TyKind::ImplTrait(..));
+                if !self.0 {
+                    walk_ty(self, t);
+                }
+            }
+        }
+
+        let mut vis = ContainsImplTrait(false);
+        vis.visit_ty(self);
+        vis.0
+    }
+}
+
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct BareFnTy {
     pub unsafety: Unsafe,

src/librustc_error_codes/error_codes/E0493.md

@@ -1,5 +1,4 @@
-A type with a `Drop` implementation was destructured when trying to initialize
-a static item.
+A value with a custom `Drop` implementation may be dropped during const-eval.
 
 Erroneous code example:
 
@@ -16,13 +15,14 @@ struct Foo {
     field1: DropType,
 }
 
-static FOO: Foo = Foo { ..Foo { field1: DropType::A } }; // error!
+static FOO: Foo = Foo { field1: (DropType::A, DropType::A).1 }; // error!
 ```
 
 The problem here is that if the given type or one of its fields implements the
-`Drop` trait, this `Drop` implementation cannot be called during the static
-type initialization which might cause a memory leak. To prevent this issue,
-you need to instantiate all the static type's fields by hand.
+`Drop` trait, this `Drop` implementation cannot be called within a const
+context since it may run arbitrary, non-const-checked code. To prevent this
+issue, ensure all values with custom a custom `Drop` implementation escape the
+initializer.
 
 ```
 enum DropType {

src/librustc_errors/diagnostic.rs

@@ -296,6 +296,29 @@ impl Diagnostic {
         self
     }
 
+    pub fn multipart_suggestions(
+        &mut self,
+        msg: &str,
+        suggestions: Vec<Vec<(Span, String)>>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        self.suggestions.push(CodeSuggestion {
+            substitutions: suggestions
+                .into_iter()
+                .map(|suggestion| Substitution {
+                    parts: suggestion
+                        .into_iter()
+                        .map(|(span, snippet)| SubstitutionPart { snippet, span })
+                        .collect(),
+                })
+                .collect(),
+            msg: msg.to_owned(),
+            style: SuggestionStyle::ShowCode,
+            applicability,
+        });
+        self
+    }
+
     /// Prints out a message with for a multipart suggestion without showing the suggested code.
     ///
     /// This is intended to be used for suggestions that are obvious in what the changes need to

src/librustc_errors/diagnostic_builder.rs

@@ -260,6 +260,19 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    pub fn multipart_suggestions(
+        &mut self,
+        msg: &str,
+        suggestions: Vec<Vec<(Span, String)>>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        if !self.0.allow_suggestions {
+            return self;
+        }
+        self.0.diagnostic.multipart_suggestions(msg, suggestions, applicability);
+        self
+    }
+
     pub fn tool_only_multipart_suggestion(
         &mut self,
         msg: &str,

src/librustc_feature/active.rs

@@ -577,6 +577,9 @@ declare_features! (
     /// Allows `extern "avr-interrupt" fn()` and `extern "avr-non-blocking-interrupt" fn()`.
     (active, abi_avr_interrupt, "1.45.0", Some(69664), None),
 
+    /// Be more precise when looking for live drops in a const context.
+    (active, const_precise_live_drops, "1.46.0", Some(73255), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------

src/librustc_interface/passes.rs

@@ -847,7 +847,11 @@ fn analysis(tcx: TyCtxt<'_>, cnum: CrateNum) -> Result<()> {
 
     sess.time("MIR_effect_checking", || {
         for def_id in tcx.body_owners() {
-            mir::transform::check_unsafety::check_unsafety(tcx, def_id)
+            mir::transform::check_unsafety::check_unsafety(tcx, def_id);
+
+            if tcx.hir().body_const_context(def_id).is_some() {
+                tcx.ensure().mir_drops_elaborated_and_const_checked(def_id);
+            }
         }
     });