Auto merge of #69442 - jakevossen5:master, r=Mark-Simulacrum

[rust.git] / src / librustc / traits / mod.rs

diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index c000aa7c25e974281826728805ce566ce958ff00..1a4ea66a5f1d979cb8ab0493b076fa0c2a841f5f 100644 (file)
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -13,11 +13,13 @@
 use crate::ty::subst::SubstsRef;
 use crate::ty::{self, AdtKind, List, Ty, TyCtxt};
 
+use rustc_ast::ast;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_span::{Span, DUMMY_SP};
-use syntax::ast;
+use smallvec::SmallVec;
 
+use std::borrow::Cow;
 use std::fmt::Debug;
 use std::rc::Rc;
 
@@ -579,6 +581,20 @@ pub fn nested_obligations(self) -> Vec<N> {
         }
     }
 
+    pub fn borrow_nested_obligations(&self) -> &[N] {
+        match &self {
+            VtableImpl(i) => &i.nested[..],
+            VtableParam(n) => &n[..],
+            VtableBuiltin(i) => &i.nested[..],
+            VtableAutoImpl(d) => &d.nested[..],
+            VtableClosure(c) => &c.nested[..],
+            VtableGenerator(c) => &c.nested[..],
+            VtableObject(d) => &d.nested[..],
+            VtableFnPointer(d) => &d.nested[..],
+            VtableTraitAlias(d) => &d.nested[..],
+        }
+    }
+
     pub fn map<M, F>(self, f: F) -> Vtable<'tcx, M>
     where
         F: FnMut(N) -> M,
@@ -737,3 +753,132 @@ fn lift_literal_to_tcx(
         tcx: TyCtxt<'tcx>,
     ) -> Option<Self::LiftedLiteral>;
 }
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash, HashStable)]
+pub enum ObjectSafetyViolation {
+    /// `Self: Sized` declared on the trait.
+    SizedSelf(SmallVec<[Span; 1]>),
+
+    /// Supertrait reference references `Self` an in illegal location
+    /// (e.g., `trait Foo : Bar<Self>`).
+    SupertraitSelf(SmallVec<[Span; 1]>),
+
+    /// Method has something illegal.
+    Method(ast::Name, MethodViolationCode, Span),
+
+    /// Associated const.
+    AssocConst(ast::Name, Span),
+}
+
+impl ObjectSafetyViolation {
+    pub fn error_msg(&self) -> Cow<'static, str> {
+        match *self {
+            ObjectSafetyViolation::SizedSelf(_) => "it requires `Self: Sized`".into(),
+            ObjectSafetyViolation::SupertraitSelf(ref spans) => {
+                if spans.iter().any(|sp| *sp != DUMMY_SP) {
+                    "it uses `Self` as a type parameter in this".into()
+                } else {
+                    "it cannot use `Self` as a type parameter in a supertrait or `where`-clause"
+                        .into()
+                }
+            }
+            ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(_), _) => {
+                format!("associated function `{}` has no `self` parameter", name).into()
+            }
+            ObjectSafetyViolation::Method(
+                name,
+                MethodViolationCode::ReferencesSelfInput(_),
+                DUMMY_SP,
+            ) => format!("method `{}` references the `Self` type in its parameters", name).into(),
+            ObjectSafetyViolation::Method(name, MethodViolationCode::ReferencesSelfInput(_), _) => {
+                format!("method `{}` references the `Self` type in this parameter", name).into()
+            }
+            ObjectSafetyViolation::Method(name, MethodViolationCode::ReferencesSelfOutput, _) => {
+                format!("method `{}` references the `Self` type in its return type", name).into()
+            }
+            ObjectSafetyViolation::Method(
+                name,
+                MethodViolationCode::WhereClauseReferencesSelf,
+                _,
+            ) => {
+                format!("method `{}` references the `Self` type in its `where` clause", name).into()
+            }
+            ObjectSafetyViolation::Method(name, MethodViolationCode::Generic, _) => {
+                format!("method `{}` has generic type parameters", name).into()
+            }
+            ObjectSafetyViolation::Method(name, MethodViolationCode::UndispatchableReceiver, _) => {
+                format!("method `{}`'s `self` parameter cannot be dispatched on", name).into()
+            }
+            ObjectSafetyViolation::AssocConst(name, DUMMY_SP) => {
+                format!("it contains associated `const` `{}`", name).into()
+            }
+            ObjectSafetyViolation::AssocConst(..) => "it contains this associated `const`".into(),
+        }
+    }
+
+    pub fn solution(&self) -> Option<(String, Option<(String, Span)>)> {
+        Some(match *self {
+            ObjectSafetyViolation::SizedSelf(_) | ObjectSafetyViolation::SupertraitSelf(_) => {
+                return None;
+            }
+            ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(sugg), _) => (
+                format!(
+                    "consider turning `{}` into a method by giving it a `&self` argument or \
+                     constraining it so it does not apply to trait objects",
+                    name
+                ),
+                sugg.map(|(sugg, sp)| (sugg.to_string(), sp)),
+            ),
+            ObjectSafetyViolation::Method(
+                name,
+                MethodViolationCode::UndispatchableReceiver,
+                span,
+            ) => (
+                format!("consider changing method `{}`'s `self` parameter to be `&self`", name),
+                Some(("&Self".to_string(), span)),
+            ),
+            ObjectSafetyViolation::AssocConst(name, _)
+            | ObjectSafetyViolation::Method(name, ..) => {
+                (format!("consider moving `{}` to another trait", name), None)
+            }
+        })
+    }
+
+    pub fn spans(&self) -> SmallVec<[Span; 1]> {
+        // When `span` comes from a separate crate, it'll be `DUMMY_SP`. Treat it as `None` so
+        // diagnostics use a `note` instead of a `span_label`.
+        match self {
+            ObjectSafetyViolation::SupertraitSelf(spans)
+            | ObjectSafetyViolation::SizedSelf(spans) => spans.clone(),
+            ObjectSafetyViolation::AssocConst(_, span)
+            | ObjectSafetyViolation::Method(_, _, span)
+                if *span != DUMMY_SP =>
+            {
+                smallvec![*span]
+            }
+            _ => smallvec![],
+        }
+    }
+}
+
+/// Reasons a method might not be object-safe.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
+pub enum MethodViolationCode {
+    /// e.g., `fn foo()`
+    StaticMethod(Option<(&'static str, Span)>),
+
+    /// e.g., `fn foo(&self, x: Self)`
+    ReferencesSelfInput(usize),
+
+    /// e.g., `fn foo(&self) -> Self`
+    ReferencesSelfOutput,
+
+    /// e.g., `fn foo(&self) where Self: Clone`
+    WhereClauseReferencesSelf,
+
+    /// e.g., `fn foo<A>()`
+    Generic,
+
+    /// the method's receiver (`self` argument) can't be dispatched on
+    UndispatchableReceiver,
+}