Rollup merge of rust-lang#125667 - oli-obk:taintify, r=TaKO8Ki

Silence follow-up errors directly based on error types and regions

During type_of, we used to just return an error type if there were any errors encountered. This is problematic, because it means a struct declared as `struct Foo<'static>` will end up not finding any inherent or trait impls because those impl blocks' `Self` type will be `{type error}` instead of `Foo<'re_error>`. Now it's the latter, silencing nonsensical follow-up errors about `Foo` not having any methods.

Unfortunately that now allows for new follow-up errors, because borrowck treats `'re_error` as `'static`, causing nonsensical errors about non-error lifetimes not outliving `'static`. So what I also did was to just strip all outlives bounds that borrowck found, thus never letting it check them. There are probably more nuanced ways to do this, but I worried there would be other nonsensical errors if some outlives bounds were missing. Also from the test changes, it looked like an improvement everywhere.

compiler/rustc_borrowck/src/nll.rs

@@ -125,8 +125,8 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
         placeholder_indices,
         placeholder_index_to_region: _,
         liveness_constraints,
-        outlives_constraints,
-        member_constraints,
+        mut outlives_constraints,
+        mut member_constraints,
         universe_causes,
         type_tests,
     } = constraints;
@@ -144,6 +144,16 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
         &universal_region_relations,
     );
 
+    if let Some(guar) = universal_regions.tainted_by_errors() {
+        // Suppress unhelpful extra errors in `infer_opaque_types` by clearing out all
+        // outlives bounds that we may end up checking.
+        outlives_constraints = Default::default();
+        member_constraints = Default::default();
+
+        // Also taint the entire scope.
+        infcx.set_tainted_by_errors(guar);
+    }
+
     let mut regioncx = RegionInferenceContext::new(
         infcx,
         var_origins,

compiler/rustc_borrowck/src/universal_regions.rs

@@ -29,7 +29,8 @@ use rustc_middle::ty::{self, InlineConstArgs, InlineConstArgsParts, RegionVid, T
 use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_middle::{bug, span_bug};
 use rustc_span::symbol::{kw, sym};
-use rustc_span::Symbol;
+use rustc_span::{ErrorGuaranteed, Symbol};
+use std::cell::Cell;
 use std::iter;
 
 use crate::renumber::RegionCtxt;
@@ -186,6 +187,10 @@ struct UniversalRegionIndices<'tcx> {
 
     /// The vid assigned to `'static`. Used only for diagnostics.
     pub fr_static: RegionVid,
+
+    /// Whether we've encountered an error region. If we have, cancel all
+    /// outlives errors, as they are likely bogus.
+    pub tainted_by_errors: Cell<Option<ErrorGuaranteed>>,
 }
 
 #[derive(Debug, PartialEq)]
@@ -408,6 +413,10 @@ impl<'tcx> UniversalRegions<'tcx> {
             }
         }
     }
+
+    pub fn tainted_by_errors(&self) -> Option<ErrorGuaranteed> {
+        self.indices.tainted_by_errors.get()
+    }
 }
 
 struct UniversalRegionsBuilder<'cx, 'tcx> {
@@ -663,7 +672,11 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
         let global_mapping = iter::once((tcx.lifetimes.re_static, fr_static));
         let arg_mapping = iter::zip(identity_args.regions(), fr_args.regions().map(|r| r.as_var()));
 
-        UniversalRegionIndices { indices: global_mapping.chain(arg_mapping).collect(), fr_static }
+        UniversalRegionIndices {
+            indices: global_mapping.chain(arg_mapping).collect(),
+            fr_static,
+            tainted_by_errors: Cell::new(None),
+        }
     }
 
     fn compute_inputs_and_output(
@@ -868,7 +881,8 @@ impl<'tcx> UniversalRegionIndices<'tcx> {
     pub fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
         if let ty::ReVar(..) = *r {
             r.as_var()
-        } else if r.is_error() {
+        } else if let ty::ReError(guar) = *r {
+            self.tainted_by_errors.set(Some(guar));
             // We use the `'static` `RegionVid` because `ReError` doesn't actually exist in the
             // `UniversalRegionIndices`. This is fine because 1) it is a fallback only used if
             // errors are being emitted and 2) it leaves the happy path unaffected.

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -502,7 +502,9 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_
             bug!("unexpected sort of node in type_of(): {:?}", x);
         }
     };
-    if let Err(e) = icx.check_tainted_by_errors() {
+    if let Err(e) = icx.check_tainted_by_errors()
+        && !output.references_error()
+    {
         ty::EarlyBinder::bind(Ty::new_error(tcx, e))
     } else {
         ty::EarlyBinder::bind(output)

tests/rustdoc-ui/unable-fulfill-trait.rs

@@ -1,13 +1,16 @@
 // This test ensures that it's not crashing rustdoc.
 
 pub struct Foo<'a, 'b, T> {
-    field1: dyn Bar<'a, 'b,>,
+    field1: dyn Bar<'a, 'b>,
     //~^ ERROR
     //~| ERROR
+    //~| ERROR
 }
 
 pub trait Bar<'x, 's, U>
-    where U: 'x,
-    Self:'x,
-    Self:'s
-{}
+where
+    U: 'x,
+    Self: 'x,
+    Self: 's,
+{
+}

tests/rustdoc-ui/unable-fulfill-trait.stderr

@@ -1,26 +1,43 @@
 error[E0107]: trait takes 1 generic argument but 0 generic arguments were supplied
   --> $DIR/unable-fulfill-trait.rs:4:17
    |
-LL |     field1: dyn Bar<'a, 'b,>,
+LL |     field1: dyn Bar<'a, 'b>,
    |                 ^^^ expected 1 generic argument
    |
 note: trait defined here, with 1 generic parameter: `U`
-  --> $DIR/unable-fulfill-trait.rs:9:11
+  --> $DIR/unable-fulfill-trait.rs:10:11
    |
 LL | pub trait Bar<'x, 's, U>
    |           ^^^         -
 help: add missing generic argument
    |
-LL |     field1: dyn Bar<'a, 'b, U,>,
+LL |     field1: dyn Bar<'a, 'b, U>,
    |                           +++
 
 error[E0227]: ambiguous lifetime bound, explicit lifetime bound required
   --> $DIR/unable-fulfill-trait.rs:4:13
    |
-LL |     field1: dyn Bar<'a, 'b,>,
-   |             ^^^^^^^^^^^^^^^^
+LL |     field1: dyn Bar<'a, 'b>,
+   |             ^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error[E0478]: lifetime bound not satisfied
+  --> $DIR/unable-fulfill-trait.rs:4:13
+   |
+LL |     field1: dyn Bar<'a, 'b>,
+   |             ^^^^^^^^^^^^^^^
+   |
+note: lifetime parameter instantiated with the lifetime `'b` as defined here
+  --> $DIR/unable-fulfill-trait.rs:3:20
+   |
+LL | pub struct Foo<'a, 'b, T> {
+   |                    ^^
+note: but lifetime parameter must outlive the lifetime `'a` as defined here
+  --> $DIR/unable-fulfill-trait.rs:3:16
+   |
+LL | pub struct Foo<'a, 'b, T> {
+   |                ^^
+
+error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0107, E0227.
+Some errors have detailed explanations: E0107, E0227, E0478.
 For more information about an error, try `rustc --explain E0107`.

tests/ui/associated-inherent-types/issue-109071.rs

@@ -13,7 +13,7 @@ impl<T> Windows { //~ ERROR: missing generics for struct `Windows`
 
 impl<T> Windows<T> {
     fn T() -> Option<Self::Item> {}
-    //~^ ERROR: ambiguous associated type
+    //[no_gate]~^ ERROR: ambiguous associated type
 }
 
 fn main() {}

tests/ui/associated-inherent-types/issue-109071.with_gate.stderr

@@ -20,20 +20,7 @@ help: add missing generic argument
 LL | impl<T> Windows<T> {
    |                +++
 
-error[E0223]: ambiguous associated type
-  --> $DIR/issue-109071.rs:15:22
-   |
-LL |     fn T() -> Option<Self::Item> {}
-   |                      ^^^^^^^^^^
-   |
-help: use fully-qualified syntax
-   |
-LL |     fn T() -> Option<<Windows<T> as IntoAsyncIterator>::Item> {}
-   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-LL |     fn T() -> Option<<Windows<T> as IntoIterator>::Item> {}
-   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0107, E0223, E0637.
+Some errors have detailed explanations: E0107, E0637.
 For more information about an error, try `rustc --explain E0107`.

tests/ui/associated-inherent-types/issue-109299.rs

@@ -8,6 +8,5 @@ impl Lexer<'d> { //~ ERROR use of undeclared lifetime name `'d`
 }
 
 fn test(_: Lexer::Cursor) {}
-//~^ ERROR: lifetime may not live long enough
 
 fn main() {}

tests/ui/associated-inherent-types/issue-109299.stderr

@@ -6,15 +6,6 @@ LL | impl Lexer<'d> {
    |     |
    |     help: consider introducing lifetime `'d` here: `<'d>`
 
-error: lifetime may not live long enough
-  --> $DIR/issue-109299.rs:10:1
-   |
-LL | fn test(_: Lexer::Cursor) {}
-   | ^^^^^^^^-^^^^^^^^^^^^^^^^
-   | |       |
-   | |       has type `Lexer<'1>::Cursor`
-   | requires that `'1` must outlive `'static`
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0261`.

tests/ui/borrowck/generic_const_early_param.rs

@@ -5,7 +5,6 @@ struct DataWrapper<'static> {
     //~^ ERROR invalid lifetime parameter name: `'static`
     data: &'a [u8; Self::SIZE],
     //~^ ERROR use of undeclared lifetime name `'a`
-    //~^^ ERROR lifetime may not live long enough
 }
 
 impl DataWrapper<'a> {

tests/ui/borrowck/generic_const_early_param.stderr

@@ -14,7 +14,7 @@ LL |     data: &'a [u8; Self::SIZE],
    |            ^^ undeclared lifetime
 
 error[E0261]: use of undeclared lifetime name `'a`
-  --> $DIR/generic_const_early_param.rs:11:18
+  --> $DIR/generic_const_early_param.rs:10:18
    |
 LL | impl DataWrapper<'a> {
    |     -            ^^ undeclared lifetime
@@ -30,13 +30,7 @@ LL | #![feature(generic_const_exprs)]
    = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
    = note: `#[warn(incomplete_features)]` on by default
 
-error: lifetime may not live long enough
-  --> $DIR/generic_const_early_param.rs:6:20
-   |
-LL |     data: &'a [u8; Self::SIZE],
-   |                    ^^^^^^^^^^ requires that `'_` must outlive `'static`
-
-error: aborting due to 4 previous errors; 1 warning emitted
+error: aborting due to 3 previous errors; 1 warning emitted
 
 Some errors have detailed explanations: E0261, E0262.
 For more information about an error, try `rustc --explain E0261`.

tests/ui/const-generics/issues/issue-71381.full.stderr

@@ -7,7 +7,7 @@ LL |     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "
    = note: type parameters may not be used in the type of const parameters
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
-  --> $DIR/issue-71381.rs:22:40
+  --> $DIR/issue-71381.rs:23:40
    |
 LL |         const FN: unsafe extern "C" fn(Args),
    |                                        ^^^^ the type must not depend on the parameter `Args`

tests/ui/const-generics/issues/issue-71381.min.stderr

@@ -7,13 +7,29 @@ LL |     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "
    = note: type parameters may not be used in the type of const parameters
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
-  --> $DIR/issue-71381.rs:22:40
+  --> $DIR/issue-71381.rs:23:40
    |
 LL |         const FN: unsafe extern "C" fn(Args),
    |                                        ^^^^ the type must not depend on the parameter `Args`
    |
    = note: type parameters may not be used in the type of const parameters
 
-error: aborting due to 2 previous errors
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/issue-71381.rs:14:61
+   |
+LL |     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "C" fn(Args)>(&self) {
+   |                                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/issue-71381.rs:23:19
+   |
+LL |         const FN: unsafe extern "C" fn(Args),
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0770`.

tests/ui/const-generics/issues/issue-71381.rs

@@ -13,6 +13,7 @@ unsafe extern "C" fn pass(args: PassArg) {
 impl Test {
     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "C" fn(Args)>(&self) {
         //~^ ERROR: the type of const parameters must not depend on other generic parameters
+        //[min]~^^ ERROR: using function pointers as const generic parameters is forbidden
         self.0 = Self::trampiline::<Args, IDX, FN> as _
     }
 
@@ -21,6 +22,7 @@ impl Test {
         const IDX: usize,
         const FN: unsafe extern "C" fn(Args),
         //~^ ERROR: the type of const parameters must not depend on other generic parameters
+        //[min]~^^ ERROR: using function pointers as const generic parameters is forbidden
     >(
         args: Args,
     ) {

tests/ui/const-generics/issues/issue-71611.min.stderr

@@ -6,6 +6,14 @@ LL | fn func<A, const F: fn(inner: A)>(outer: A) {
    |
    = note: type parameters may not be used in the type of const parameters
 
-error: aborting due to 1 previous error
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/issue-71611.rs:5:21
+   |
+LL | fn func<A, const F: fn(inner: A)>(outer: A) {
+   |                     ^^^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0770`.

tests/ui/const-generics/issues/issue-71611.rs

@@ -4,6 +4,7 @@
 
 fn func<A, const F: fn(inner: A)>(outer: A) {
     //~^ ERROR: the type of const parameters must not depend on other generic parameters
+    //[min]~| ERROR: using function pointers as const generic parameters is forbidden
     F(outer);
 }
 

tests/ui/const_prop/ice-type-mismatch-when-copying-112824.rs

@@ -13,6 +13,7 @@ impl Opcode2 {
 pub fn example2(msg_type: Opcode2) -> impl FnMut(&[u8]) {
     move |i| match msg_type {
         Opcode2::OP2 => unimplemented!(),
+        //~^ ERROR: could not evaluate constant pattern
     }
 }
 

tests/ui/const_prop/ice-type-mismatch-when-copying-112824.stderr

@@ -17,7 +17,13 @@ help: you might be missing a type parameter
 LL | pub struct Opcode2<S>(&'a S);
    |                   +++
 
-error: aborting due to 2 previous errors
+error: could not evaluate constant pattern
+  --> $DIR/ice-type-mismatch-when-copying-112824.rs:15:9
+   |
+LL |         Opcode2::OP2 => unimplemented!(),
+   |         ^^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
 
 Some errors have detailed explanations: E0261, E0412.
 For more information about an error, try `rustc --explain E0261`.

tests/ui/generic-associated-types/gat-trait-path-missing-lifetime.rs

@@ -9,7 +9,6 @@ impl<T> X for T { //~ ERROR: not all trait items implemented
     //~^ ERROR missing generics for associated type
     //~^^ ERROR missing generics for associated type
     //~| ERROR method `foo` has 1 type parameter but its trait declaration has 0 type parameters
-    //~| ERROR may not live long enough
     t
   }
 }

tests/ui/generic-associated-types/gat-trait-path-missing-lifetime.stderr

@@ -51,16 +51,7 @@ help: add missing lifetime argument
 LL |   fn foo<'a, T1: X<Y<'a> = T1>>(t : T1) -> T1::Y<'a> {
    |                     ++++
 
-error: lifetime may not live long enough
-  --> $DIR/gat-trait-path-missing-lifetime.rs:8:3
-   |
-LL |   fn foo<'a, T1: X<Y = T1>>(t : T1) -> T1::Y<'a> {
-   |   ^^^^^^^--^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |   |      |
-   |   |      lifetime `'a` defined here
-   |   requires that `'a` must outlive `'static`
-
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0046, E0049, E0107.
 For more information about an error, try `rustc --explain E0046`.

tests/ui/generic-associated-types/issue-70304.rs

@@ -52,5 +52,4 @@ fn create_doc() -> impl Document<Cursor<'_> = DocCursorImpl<'_>> {
 pub fn main() {
     let doc = create_doc();
     let lexer: Lexer<'_, DocCursorImpl<'_>> = Lexer::from(&doc);
-    //~^ ERROR: `doc` does not live long enough
 }