Rollup merge of rust-lang#73783 - estebank:impl-dyn-trait-static-lifetime, r=nikomatsakis

Detect when `'static` obligation might come from an `impl`

Partly address rust-lang#71341.

Author: Manishearth

src/librustc_error_codes/error_codes.rs

@@ -633,4 +633,5 @@ E0771: include_str!("./error_codes/E0771.md"),
     E0755, // `#[ffi_pure]` is only allowed on foreign functions
     E0756, // `#[ffi_const]` is only allowed on foreign functions
     E0757, // `#[ffi_const]` functions cannot be `#[ffi_pure]`
+    E0772, // `'static' obligation coming from `impl dyn Trait {}` or `impl Foo for dyn Bar {}`.
 }

src/librustc_hir/hir.rs

@@ -2198,7 +2198,17 @@ pub enum IsAsync {
     NotAsync,
 }
 
-#[derive(Copy, Clone, PartialEq, RustcEncodable, RustcDecodable, Debug, HashStable_Generic)]
+#[derive(
+    Copy,
+    Clone,
+    PartialEq,
+    RustcEncodable,
+    RustcDecodable,
+    Debug,
+    HashStable_Generic,
+    Eq,
+    Hash
+)]
 pub enum Defaultness {
     Default { has_value: bool },
     Final,

src/librustc_infer/infer/combine.rs

@@ -36,12 +36,13 @@ use crate::traits::{Obligation, PredicateObligations};
 
 use rustc_ast::ast;
 use rustc_hir::def_id::DefId;
+use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation};
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, InferConst, ToPredicate, Ty, TyCtxt, TypeFoldable};
 use rustc_middle::ty::{IntType, UintType};
-use rustc_span::{Span, DUMMY_SP};
+use rustc_span::DUMMY_SP;
 
 #[derive(Clone)]
 pub struct CombineFields<'infcx, 'tcx> {
@@ -367,10 +368,11 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> {
         };
 
         debug!("generalize: for_universe = {:?}", for_universe);
+        debug!("generalize: trace = {:?}", self.trace);
 
         let mut generalize = Generalizer {
             infcx: self.infcx,
-            span: self.trace.cause.span,
+            cause: &self.trace.cause,
             for_vid_sub_root: self.infcx.inner.borrow_mut().type_variables().sub_root_var(for_vid),
             for_universe,
             ambient_variance,
@@ -414,7 +416,7 @@ struct Generalizer<'cx, 'tcx> {
     infcx: &'cx InferCtxt<'cx, 'tcx>,
 
     /// The span, used when creating new type variables and things.
-    span: Span,
+    cause: &'cx ObligationCause<'tcx>,
 
     /// The vid of the type variable that is in the process of being
     /// instantiated; if we find this within the type we are folding,
@@ -639,7 +641,7 @@ impl TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
 
         // FIXME: This is non-ideal because we don't give a
         // very descriptive origin for this region variable.
-        Ok(self.infcx.next_region_var_in_universe(MiscVariable(self.span), self.for_universe))
+        Ok(self.infcx.next_region_var_in_universe(MiscVariable(self.cause.span), self.for_universe))
     }
 
     fn consts(

src/librustc_infer/infer/error_reporting/mod.rs

@@ -2010,7 +2010,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             infer::MiscVariable(_) => String::new(),
             infer::PatternRegion(_) => " for pattern".to_string(),
             infer::AddrOfRegion(_) => " for borrow expression".to_string(),
-            infer::Autoref(_) => " for autoref".to_string(),
+            infer::Autoref(_, _) => " for autoref".to_string(),
             infer::Coercion(_) => " for automatic coercion".to_string(),
             infer::LateBoundRegion(_, br, infer::FnCall) => {
                 format!(" for lifetime parameter {}in function call", br_string(br))