Create a single long-lived InferCtxt for ItemCtxt

Author: oli-obk

compiler/rustc_hir_analysis/src/collect.rs

@@ -38,7 +38,6 @@ use rustc_target::spec::abi;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
 use rustc_trait_selection::traits::ObligationCtxt;
-use std::cell::Cell;
 use std::iter;
 use std::ops::Bound;
 
@@ -120,7 +119,7 @@ pub fn provide(providers: &mut Providers) {
 pub struct ItemCtxt<'tcx> {
     tcx: TyCtxt<'tcx>,
     item_def_id: LocalDefId,
-    tainted_by_errors: Cell<Option<ErrorGuaranteed>>,
+    infcx: InferCtxt<'tcx>,
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -342,7 +341,7 @@ fn bad_placeholder<'tcx>(
 
 impl<'tcx> ItemCtxt<'tcx> {
     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: LocalDefId) -> ItemCtxt<'tcx> {
-        ItemCtxt { tcx, item_def_id, tainted_by_errors: Cell::new(None) }
+        ItemCtxt { tcx, item_def_id, infcx: tcx.infer_ctxt().ignoring_regions().build() }
     }
 
     pub fn lower_ty(&self, hir_ty: &hir::Ty<'tcx>) -> Ty<'tcx> {
@@ -358,7 +357,7 @@ impl<'tcx> ItemCtxt<'tcx> {
     }
 
     fn check_tainted_by_errors(&self) -> Result<(), ErrorGuaranteed> {
-        match self.tainted_by_errors.get() {
+        match self.infcx.tainted_by_errors() {
             Some(err) => Err(err),
             None => Ok(()),
         }
@@ -503,12 +502,8 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
         // There's no place to record types from signatures?
     }
 
-    fn infcx(&self) -> Option<&InferCtxt<'tcx>> {
-        None
-    }
-
-    fn set_tainted_by_errors(&self, err: ErrorGuaranteed) {
-        self.tainted_by_errors.set(Some(err));
+    fn infcx(&self) -> &InferCtxt<'tcx> {
+        &self.infcx
     }
 }
 

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -36,7 +36,7 @@ use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{walk_generics, Visitor as _};
 use rustc_hir::{GenericArg, GenericArgs, HirId};
-use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
+use rustc_infer::infer::InferCtxt;
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::middle::stability::AllowUnstable;
 use rustc_middle::mir::interpret::{LitToConstError, LitToConstInput};
@@ -162,14 +162,16 @@ pub trait HirTyLowerer<'tcx> {
     /// Record the lowered type of a HIR node in this context.
     fn record_ty(&self, hir_id: HirId, ty: Ty<'tcx>, span: Span);
 
-    /// The inference context of the lowering context if applicable.
-    fn infcx(&self) -> Option<&InferCtxt<'tcx>>;
+    /// The inference context of the lowering context.
+    fn infcx(&self) -> &InferCtxt<'tcx>;
 
     /// Taint the context with errors.
     ///
     /// Invoke this when you encounter an error from some prior pass like name resolution.
     /// This is used to help suppress derived errors typeck might otherwise report.
-    fn set_tainted_by_errors(&self, e: ErrorGuaranteed);
+    fn set_tainted_by_errors(&self, e: ErrorGuaranteed) {
+        self.infcx().set_tainted_by_errors(e);
+    }
 
     /// Convenience method for coercing the lowering context into a trait object type.
     ///
@@ -1226,17 +1228,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // Select applicable inherent associated type candidates modulo regions.
         //
 
-        // In contexts that have no inference context, just make a new one.
-        // We do need a local variable to store it, though.
-        let infcx_;
-        let infcx = match self.infcx() {
-            Some(infcx) => infcx,
-            None => {
-                assert!(!self_ty.has_infer());
-                infcx_ = tcx.infer_ctxt().ignoring_regions().build();
-                &infcx_
-            }
-        };
+        let infcx = self.infcx();
+        assert!(self.allow_infer() || !self_ty.has_infer());
 
         // FIXME(inherent_associated_types): Acquiring the ParamEnv this early leads to cycle errors
         // when inside of an ADT (#108491) or where clause.
@@ -1399,16 +1392,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     ) -> Vec<String> {
         let tcx = self.tcx();
 
-        // In contexts that have no inference context, just make a new one.
-        // We do need a local variable to store it, though.
-        let infcx_;
-        let infcx = if let Some(infcx) = self.infcx() {
-            infcx
-        } else {
-            assert!(!qself_ty.has_infer());
-            infcx_ = tcx.infer_ctxt().build();
-            &infcx_
-        };
+        let infcx = self.infcx();
+        assert!(self.allow_infer() || !qself_ty.has_infer());
 
         tcx.all_traits()
             .filter(|trait_def_id| {

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -343,8 +343,8 @@ impl<'a, 'tcx> HirTyLowerer<'tcx> for FnCtxt<'a, 'tcx> {
         self.write_ty(hir_id, ty)
     }
 
-    fn infcx(&self) -> Option<&infer::InferCtxt<'tcx>> {
-        Some(&self.infcx)
+    fn infcx(&self) -> &infer::InferCtxt<'tcx> {
+        &self.infcx
     }
 
     fn set_tainted_by_errors(&self, e: ErrorGuaranteed) {

tests/ui/issues/issue-34373.rs

@@ -6,7 +6,6 @@ trait Trait<T> {
 
 pub struct Foo<T = Box<Trait<DefaultFoo>>>;  //~ ERROR cycle detected
 //~^ ERROR `T` is never used
-//~| ERROR `Trait` cannot be made into an object
 type DefaultFoo = Foo;
 
 fn main() {

tests/ui/issues/issue-34373.stderr

@@ -5,7 +5,7 @@ LL | pub struct Foo<T = Box<Trait<DefaultFoo>>>;
    |                              ^^^^^^^^^^
    |
 note: ...which requires expanding type alias `DefaultFoo`...
-  --> $DIR/issue-34373.rs:10:19
+  --> $DIR/issue-34373.rs:9:19
    |
 LL | type DefaultFoo = Foo;
    |                   ^^^
@@ -17,28 +17,6 @@ LL | pub struct Foo<T = Box<Trait<DefaultFoo>>>;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
-error[E0038]: the trait `Trait` cannot be made into an object
-  --> $DIR/issue-34373.rs:7:24
-   |
-LL | pub struct Foo<T = Box<Trait<DefaultFoo>>>;
-   |                        ^^^^^^^^^^^^^^^^^ `Trait` cannot be made into an object
-   |
-note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
-  --> $DIR/issue-34373.rs:4:8
-   |
-LL | trait Trait<T> {
-   |       ----- this trait cannot be made into an object...
-LL |     fn foo(_: T) {}
-   |        ^^^ ...because associated function `foo` has no `self` parameter
-help: consider turning `foo` into a method by giving it a `&self` argument
-   |
-LL |     fn foo(&self, _: T) {}
-   |            ++++++
-help: alternatively, consider constraining `foo` so it does not apply to trait objects
-   |
-LL |     fn foo(_: T) where Self: Sized {}
-   |                  +++++++++++++++++
-
 error[E0392]: type parameter `T` is never used
   --> $DIR/issue-34373.rs:7:16
    |
@@ -48,7 +26,7 @@ LL | pub struct Foo<T = Box<Trait<DefaultFoo>>>;
    = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
    = help: if you intended `T` to be a const parameter, use `const T: /* Type */` instead
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0038, E0391, E0392.
-For more information about an error, try `rustc --explain E0038`.
+Some errors have detailed explanations: E0391, E0392.
+For more information about an error, try `rustc --explain E0391`.

tests/ui/traits/issue-106072.rs

@@ -1,6 +1,5 @@
 #[derive(Clone)] //~  trait objects must include the `dyn` keyword
-//~^ ERROR: the size for values of type `(dyn Foo + 'static)` cannot be known
-//~| ERROR: return type cannot have an unboxed trait object
+//~^ ERROR: return type cannot have an unboxed trait object
 struct Foo;
 trait Foo {} //~ the name `Foo` is defined multiple times
 fn main() {}

tests/ui/traits/issue-106072.stderr

@@ -1,5 +1,5 @@
 error[E0428]: the name `Foo` is defined multiple times
-  --> $DIR/issue-106072.rs:5:1
+  --> $DIR/issue-106072.rs:4:1
    |
 LL | struct Foo;
    | ----------- previous definition of the type `Foo` here
@@ -8,17 +8,6 @@ LL | trait Foo {}
    |
    = note: `Foo` must be defined only once in the type namespace of this module
 
-error[E0277]: the size for values of type `(dyn Foo + 'static)` cannot be known at compilation time
-  --> $DIR/issue-106072.rs:1:10
-   |
-LL | #[derive(Clone)]
-   |          ^^^^^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `(dyn Foo + 'static)`
-note: required by a bound in `Clone`
-  --> $SRC_DIR/core/src/clone.rs:LL:COL
-   = note: this error originates in the derive macro `Clone` (in Nightly builds, run with -Z macro-backtrace for more info)
-
 error[E0746]: return type cannot have an unboxed trait object
   --> $DIR/issue-106072.rs:1:10
    |
@@ -35,7 +24,7 @@ LL | #[derive(Clone)]
    |
    = note: this error originates in the derive macro `Clone` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0277, E0428, E0746, E0782.
-For more information about an error, try `rustc --explain E0277`.
+Some errors have detailed explanations: E0428, E0746, E0782.
+For more information about an error, try `rustc --explain E0428`.

tests/ui/typeof/type_mismatch.rs

@@ -4,6 +4,4 @@ fn main() {
     const a: u8 = 1;
     let b: typeof(a) = 1i8;
     //~^ ERROR `typeof` is a reserved keyword but unimplemented
-    //~| ERROR mismatched types
-    //~| expected `u8`, found `i8`
 }

tests/ui/typeof/type_mismatch.stderr

@@ -9,20 +9,6 @@ help: consider replacing `typeof(...)` with an actual type
 LL |     let b: u8 = 1i8;
    |            ~~
 
-error[E0308]: mismatched types
-  --> $DIR/type_mismatch.rs:5:24
-   |
-LL |     let b: typeof(a) = 1i8;
-   |            ---------   ^^^ expected `u8`, found `i8`
-   |            |
-   |            expected due to this
-   |
-help: change the type of the numeric literal from `i8` to `u8`
-   |
-LL |     let b: typeof(a) = 1u8;
-   |                         ~~
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0308, E0516.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0516`.

tests/ui/wf/ice-hir-wf-check-anon-const-issue-122199.rs

@@ -2,12 +2,6 @@ trait Trait<const N: Trait = bar> {
     //~^ ERROR cannot find value `bar` in this scope
     //~| ERROR cycle detected when computing type of `Trait::N`
     //~| ERROR cycle detected when computing type of `Trait::N`
-    //~| ERROR the trait `Trait` cannot be made into an object
-    //~| ERROR the trait `Trait` cannot be made into an object
-    //~| ERROR the trait `Trait` cannot be made into an object
-    //~| ERROR `(dyn Trait<{const error}> + 'static)` is forbidden as the type of a const generic parameter
-    //~| WARN trait objects without an explicit `dyn` are deprecated [bare_trait_objects]
-    //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
     //~| WARN trait objects without an explicit `dyn` are deprecated [bare_trait_objects]
     //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
     fn fnc<const N: Trait = u32>(&self) -> Trait {
@@ -23,6 +17,7 @@ trait Trait<const N: Trait = bar> {
     //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
     //~| WARN trait objects without an explicit `dyn` are deprecated [bare_trait_objects]
     //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+    //~| ERROR `Trait` cannot be made into an object
         bar
     //~^ ERROR cannot find value `bar` in this scope
     }