Don't stop evaluating due to errors before borrow checking

src/librustc/traits/codegen/mod.rs

@@ -5,9 +5,7 @@
 
 use crate::dep_graph::{DepKind, DepTrackingMapConfig};
 use std::marker::PhantomData;
-use syntax_pos::DUMMY_SP;
 use crate::infer::InferCtxt;
-use syntax_pos::Span;
 use crate::traits::{FulfillmentContext, Obligation, ObligationCause, SelectionContext,
              TraitEngine, Vtable};
 use crate::ty::{self, Ty, TyCtxt};
@@ -69,7 +67,7 @@ pub fn codegen_fulfill_obligation<'a, 'tcx>(ty: TyCtxt<'a, 'tcx, 'tcx>,
             debug!("fulfill_obligation: register_predicate_obligation {:?}", predicate);
             fulfill_cx.register_predicate_obligation(&infcx, predicate);
         });
-        let vtable = infcx.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &vtable);
+        let vtable = infcx.drain_fulfillment_cx_or_panic(&mut fulfill_cx, &vtable);
 
         info!("Cache miss: {:?} => {:?}", trait_ref, vtable);
         vtable
@@ -141,7 +139,6 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     /// unified, and hence we need to process those obligations to get
     /// the complete picture of the type.
     fn drain_fulfillment_cx_or_panic<T>(&self,
-                                        span: Span,
                                         fulfill_cx: &mut FulfillmentContext<'tcx>,
                                         result: &T)
                                         -> T::Lifted
@@ -153,15 +150,14 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         // contains unbound type parameters. It could be a slight
         // optimization to stop iterating early.
         if let Err(errors) = fulfill_cx.select_all_or_error(self) {
-            span_bug!(span, "Encountered errors `{:?}` resolving bounds after type-checking",
-                      errors);
+            bug!("Encountered errors `{:?}` resolving bounds after type-checking", errors);
         }
 
         let result = self.resolve_type_vars_if_possible(result);
         let result = self.tcx.erase_regions(&result);
 
         self.tcx.lift_to_global(&result).unwrap_or_else(||
-            span_bug!(span, "Uninferred types/regions in `{:?}`", result)
+            bug!("Uninferred types/regions in `{:?}`", result)
         )
     }
 }

src/librustc/ty/sty.rs

@@ -85,7 +85,7 @@ impl BoundRegion {
 /// N.B., if you change this, you'll probably want to change the corresponding
 /// AST structure in `libsyntax/ast.rs` as well.
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash,
-         RustcEncodable, RustcDecodable, HashStable)]
+         RustcEncodable, RustcDecodable, HashStable, Debug)]
 pub enum TyKind<'tcx> {
     /// The primitive boolean type. Written as `bool`.
     Bool,

src/librustc_interface/passes.rs

@@ -936,13 +936,6 @@ fn analysis<'tcx>(
         });
     });
 
-    // Abort so we don't try to construct MIR with liveness errors.
-    // We also won't want to continue with errors from rvalue promotion
-    // We only do so if the only error found so far *isn't* a missing `fn main()`
-    if !(entry_point.is_none() && sess.err_count() == 1) {
-        tcx.sess.abort_if_errors();
-    }
-
     time(sess, "borrow checking", || {
         if tcx.use_ast_borrowck() {
             borrowck::check_crate(tcx);

src/librustc_mir/hair/pattern/_match.rs

@@ -211,6 +211,7 @@ impl<'a, 'tcx> LiteralExpander<'a, 'tcx> {
         // the constant's pointee type
         crty: Ty<'tcx>,
     ) -> ConstValue<'tcx> {
+        debug!("fold_const_value_deref {:?} {:?} {:?}", val, rty, crty);
         match (val, &crty.sty, &rty.sty) {
             // the easy case, deref a reference
             (ConstValue::Scalar(Scalar::Ptr(p)), x, y) if x == y => ConstValue::ByRef(
@@ -238,6 +239,7 @@ impl<'a, 'tcx> LiteralExpander<'a, 'tcx> {
 
 impl<'a, 'tcx> PatternFolder<'tcx> for LiteralExpander<'a, 'tcx> {
     fn fold_pattern(&mut self, pat: &Pattern<'tcx>) -> Pattern<'tcx> {
+        debug!("fold_pattern {:?} {:?} {:?}", pat, pat.ty.sty, pat.kind);
         match (&pat.ty.sty, &*pat.kind) {
             (
                 &ty::Ref(_, rty, _),

src/librustc_mir/hair/pattern/check_match.rs

@@ -603,7 +603,9 @@ fn check_legality_of_move_bindings(
             E0009,
             "cannot bind by-move and by-ref in the same pattern",
         );
-        err.span_label(by_ref_span.unwrap(), "both by-ref and by-move used");
+        if let Some(by_ref_span) = by_ref_span {
+            err.span_label(by_ref_span, "both by-ref and by-move used");
+        }
         for span in span_vec.iter(){
             err.span_label(*span, "by-move pattern here");
         }

src/librustc_mir/hair/pattern/mod.rs

@@ -974,10 +974,27 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
                 PatternKind::Wild
             }
             ty::Adt(adt_def, _) if !self.tcx.has_attr(adt_def.did, "structural_match") => {
-                let msg = format!("to use a constant of type `{}` in a pattern, \
-                                    `{}` must be annotated with `#[derive(PartialEq, Eq)]`",
-                                    self.tcx.def_path_str(adt_def.did),
-                                    self.tcx.def_path_str(adt_def.did));
+                let path = self.tcx.def_path_str(adt_def.did);
+                let msg = format!(
+                    "to use a constant of type `{}` in a pattern, \
+                     `{}` must be annotated with `#[derive(PartialEq, Eq)]`",
+                    path,
+                    path,
+                );
+                self.tcx.sess.span_err(span, &msg);
+                PatternKind::Wild
+            }
+            ty::Ref(_, ty::TyS { sty: ty::Adt(adt_def, _), .. }, _)
+            if !self.tcx.has_attr(adt_def.did, "structural_match") => {
+                // HACK(estebank): Side-step ICE #53708, but anything other than erroring here
+                // would be wrong. Returnging `PatternKind::Wild` is not technically correct.
+                let path = self.tcx.def_path_str(adt_def.did);
+                let msg = format!(
+                    "to use a constant of type `{}` in a pattern, \
+                     `{}` must be annotated with `#[derive(PartialEq, Eq)]`",
+                    path,
+                    path,
+                );
                 self.tcx.sess.span_err(span, &msg);
                 PatternKind::Wild
             }

src/librustc_mir/transform/qualify_consts.rs

@@ -1502,9 +1502,11 @@ impl MirPass for QualifyAndPromoteConstants {
                                 tcx.sess,
                                 span,
                                 E0723,
-                                "{} (see issue #57563)",
+                                "{}",
                                 err,
                             );
+                            diag.note("for more information, see issue \
+                                       /~https://github.com/rust-lang/rust/issues/57563");
                             diag.help(
                                 "add #![feature(const_fn)] to the crate attributes to enable",
                             );

src/test/ui/borrowck/borrowck-mutate-in-guard.rs

@@ -9,9 +9,15 @@ fn foo() -> isize {
     match x {
         Enum::A(_) if { x = Enum::B(false); false } => 1,
         //~^ ERROR cannot assign in a pattern guard
+        //~| WARN cannot assign `x` in match guard
+        //~| WARN this error has been downgraded to a warning for backwards compatibility
+        //~| WARN this represents potential undefined behavior in your code and this warning will
         Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
         //~^ ERROR cannot mutably borrow in a pattern guard
-        //~^^ ERROR cannot assign in a pattern guard
+        //~| ERROR cannot assign in a pattern guard
+        //~| WARN cannot mutably borrow `x` in match guard
+        //~| WARN this error has been downgraded to a warning for backwards compatibility
+        //~| WARN this represents potential undefined behavior in your code and this warning will
         Enum::A(p) => *p,
         Enum::B(_) => 2,
     }

src/test/ui/borrowck/borrowck-mutate-in-guard.stderr

@@ -5,20 +5,43 @@ LL |         Enum::A(_) if { x = Enum::B(false); false } => 1,
    |                         ^^^^^^^^^^^^^^^^^^ assignment in pattern guard
 
 error[E0301]: cannot mutably borrow in a pattern guard
-  --> $DIR/borrowck-mutate-in-guard.rs:12:38
+  --> $DIR/borrowck-mutate-in-guard.rs:15:38
    |
 LL |         Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
    |                                      ^ borrowed mutably in pattern guard
    |
    = help: add #![feature(bind_by_move_pattern_guards)] to the crate attributes to enable
 
 error[E0302]: cannot assign in a pattern guard
-  --> $DIR/borrowck-mutate-in-guard.rs:12:41
+  --> $DIR/borrowck-mutate-in-guard.rs:15:41
    |
 LL |         Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
    |                                         ^^^^^^^^^^^^^^^^^^^ assignment in pattern guard
 
+warning[E0510]: cannot assign `x` in match guard
+  --> $DIR/borrowck-mutate-in-guard.rs:10:25
+   |
+LL |     match x {
+   |           - value is immutable in match guard
+LL |         Enum::A(_) if { x = Enum::B(false); false } => 1,
+   |                         ^^^^^^^^^^^^^^^^^^ cannot assign
+   |
+   = warning: this error has been downgraded to a warning for backwards compatibility with previous releases
+   = warning: this represents potential undefined behavior in your code and this warning will become a hard error in the future
+
+warning[E0510]: cannot mutably borrow `x` in match guard
+  --> $DIR/borrowck-mutate-in-guard.rs:15:33
+   |
+LL |     match x {
+   |           - value is immutable in match guard
+...
+LL |         Enum::A(_) if { let y = &mut x; *y = Enum::B(false); false } => 1,
+   |                                 ^^^^^^ cannot mutably borrow
+   |
+   = warning: this error has been downgraded to a warning for backwards compatibility with previous releases
+   = warning: this represents potential undefined behavior in your code and this warning will become a hard error in the future
+
 error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0301, E0302.
+Some errors have detailed explanations: E0301, E0302, E0510.
 For more information about an error, try `rustc --explain E0301`.

src/test/ui/consts/const_let_refutable.rs

@@ -1,5 +1,11 @@
 fn main() {}
 
 const fn slice([a, b]: &[i32]) -> i32 { //~ ERROR refutable pattern in function argument
-    a + b
+    a + b //~ ERROR can only call other `const fn` within a `const fn`
+    //~^ WARN use of possibly uninitialized variable: `a`
+    //~| WARN this error has been downgraded to a warning for backwards compatibility
+    //~| WARN this represents potential undefined behavior in your code and this warning will
+    //~| WARN use of possibly uninitialized variable: `b`
+    //~| WARN this error has been downgraded to a warning for backwards compatibility
+    //~| WARN this represents potential undefined behavior in your code and this warning will
 }

src/test/ui/consts/const_let_refutable.stderr

@@ -4,6 +4,34 @@ error[E0005]: refutable pattern in function argument: `&[]` not covered
 LL | const fn slice([a, b]: &[i32]) -> i32 {
    |                ^^^^^^ pattern `&[]` not covered
 
-error: aborting due to previous error
+error[E0723]: can only call other `const fn` within a `const fn`, but `const std::ops::Add::add` is not stable as `const fn`
+  --> $DIR/const_let_refutable.rs:4:5
+   |
+LL |     a + b
+   |     ^^^^^
+   |
+   = note: for more information, see issue /~https://github.com/rust-lang/rust/issues/57563
+   = help: add #![feature(const_fn)] to the crate attributes to enable
+
+warning[E0381]: use of possibly uninitialized variable: `a`
+  --> $DIR/const_let_refutable.rs:4:5
+   |
+LL |     a + b
+   |     ^ use of possibly uninitialized `a`
+   |
+   = warning: this error has been downgraded to a warning for backwards compatibility with previous releases
+   = warning: this represents potential undefined behavior in your code and this warning will become a hard error in the future
+
+warning[E0381]: use of possibly uninitialized variable: `b`
+  --> $DIR/const_let_refutable.rs:4:9
+   |
+LL |     a + b
+   |         ^ use of possibly uninitialized `b`
+   |
+   = warning: this error has been downgraded to a warning for backwards compatibility with previous releases
+   = warning: this represents potential undefined behavior in your code and this warning will become a hard error in the future
+
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0005`.
+Some errors have detailed explanations: E0005, E0381, E0723.
+For more information about an error, try `rustc --explain E0005`.

src/test/ui/consts/match_ice.rs

@@ -2,9 +2,17 @@
 
 struct S;
 
+#[derive(PartialEq, Eq)]
+struct T;
+
 fn main() {
     const C: &S = &S;
-    match C { //~ ERROR non-exhaustive
-        C => {} // this is a common bug around constants and references in patterns
+    match C {
+        C => {}
+        //~^ ERROR to use a constant of type `S` in a pattern, `S` must be annotated with
+    }
+    const K: &T = &T;
+    match K { //~ ERROR non-exhaustive patterns: `&T` not covered
+        K => {}
     }
 }

src/test/ui/consts/match_ice.stderr

@@ -1,11 +1,17 @@
-error[E0004]: non-exhaustive patterns: `&S` not covered
-  --> $DIR/match_ice.rs:7:11
+error: to use a constant of type `S` in a pattern, `S` must be annotated with `#[derive(PartialEq, Eq)]`
+  --> $DIR/match_ice.rs:11:9
    |
-LL |     match C {
-   |           ^ pattern `&S` not covered
+LL |         C => {}
+   |         ^
+
+error[E0004]: non-exhaustive patterns: `&T` not covered
+  --> $DIR/match_ice.rs:15:11
+   |
+LL |     match K {
+   |           ^ pattern `&T` not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0004`.

src/test/ui/consts/min_const_fn/bad_const_fn_body_ice.stderr

@@ -1,9 +1,10 @@
-error[E0723]: heap allocations are not allowed in const fn (see issue #57563)
+error[E0723]: heap allocations are not allowed in const fn
   --> $DIR/bad_const_fn_body_ice.rs:2:5
    |
 LL |     vec![1, 2, 3]
    |     ^^^^^^^^^^^^^
    |
+   = note: for more information, see issue /~https://github.com/rust-lang/rust/issues/57563
    = help: add #![feature(const_fn)] to the crate attributes to enable
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 

src/test/ui/consts/min_const_fn/cast_errors.stderr

@@ -1,41 +1,46 @@
-error[E0723]: unsizing casts are not allowed in const fn (see issue #57563)
+error[E0723]: unsizing casts are not allowed in const fn
   --> $DIR/cast_errors.rs:3:41
    |
 LL | const fn unsize(x: &[u8; 3]) -> &[u8] { x }
    |                                         ^
    |
+   = note: for more information, see issue /~https://github.com/rust-lang/rust/issues/57563
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: function pointers in const fn are unstable (see issue #57563)
+error[E0723]: function pointers in const fn are unstable
   --> $DIR/cast_errors.rs:5:23
    |
 LL | const fn closure() -> fn() { || {} }
    |                       ^^^^
    |
+   = note: for more information, see issue /~https://github.com/rust-lang/rust/issues/57563
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: function pointers in const fn are unstable (see issue #57563)
+error[E0723]: function pointers in const fn are unstable
   --> $DIR/cast_errors.rs:8:5
    |
 LL |     (|| {}) as fn();
    |     ^^^^^^^^^^^^^^^
    |
+   = note: for more information, see issue /~https://github.com/rust-lang/rust/issues/57563
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: function pointers in const fn are unstable (see issue #57563)
+error[E0723]: function pointers in const fn are unstable
   --> $DIR/cast_errors.rs:11:28
    |
 LL | const fn reify(f: fn()) -> unsafe fn() { f }
    |                            ^^^^^^^^^^^
    |
+   = note: for more information, see issue /~https://github.com/rust-lang/rust/issues/57563
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
-error[E0723]: function pointers in const fn are unstable (see issue #57563)
+error[E0723]: function pointers in const fn are unstable
   --> $DIR/cast_errors.rs:13:21
    |
 LL | const fn reify2() { main as unsafe fn(); }
    |                     ^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, see issue /~https://github.com/rust-lang/rust/issues/57563
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
 error: aborting due to 5 previous errors

src/test/ui/consts/min_const_fn/cmp_fn_pointers.stderr

@@ -1,9 +1,10 @@
-error[E0723]: function pointers in const fn are unstable (see issue #57563)
+error[E0723]: function pointers in const fn are unstable
   --> $DIR/cmp_fn_pointers.rs:1:14
    |
 LL | const fn cmp(x: fn(), y: fn()) -> bool {
    |              ^
    |
+   = note: for more information, see issue /~https://github.com/rust-lang/rust/issues/57563
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
 error: aborting due to previous error

src/test/ui/consts/min_const_fn/loop_ice.stderr

@@ -1,9 +1,10 @@
-error[E0723]: loops are not allowed in const fn (see issue #57563)
+error[E0723]: loops are not allowed in const fn
   --> $DIR/loop_ice.rs:2:5
    |
 LL |     loop {}
    |     ^^^^^^^
    |
+   = note: for more information, see issue /~https://github.com/rust-lang/rust/issues/57563
    = help: add #![feature(const_fn)] to the crate attributes to enable
 
 error: aborting due to previous error