Disentangle Debug and Display for Ty.

The `Debug` impl for `Ty` just calls the `Display` impl for `Ty`. This
is surprising and annoying. In particular, it means `Debug` doesn't show
as much information as `Debug` for `TyKind` does. And `Debug` is used in
some user-facing error messages, which seems bad.

This commit changes the `Debug` impl for `Ty` to call the `Debug` impl
for `TyKind`. It also does a number of follow-up changes to preserve
existing output, many of which involve inserting
`with_no_trimmed_paths!` calls. It also adds `Display` impls for
`UserType` and `Canonical`.

Some tests have changes to expected output:
- Those that use the `rustc_abi(debug)` attribute.
- Those that use the `rustc_layout(debug)` attribute.
- Those that use the `EMIT_MIR` annotation.

In each case the output is slightly uglier than before. This isn't
ideal, but it's pretty weird (particularly for the attributes) that the
output is using `Debug` in the first place. They're fairly obscure
attributes (I hadn't heard of them) so I'm not worried by this.

For `async-is-unwindsafe.stderr`, there is one line that now lacks a
full path. This is a consistency improvement, because all the other
mentions of `Context` in this test lack a path.

Author: nnethercote

compiler/rustc_borrowck/src/nll.rs

@@ -10,6 +10,7 @@ use rustc_middle::mir::{
     Body, ClosureOutlivesSubject, ClosureRegionRequirements, LocalKind, Location, Promoted,
     START_BLOCK,
 };
+use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, OpaqueHiddenType, TyCtxt};
 use rustc_span::symbol::sym;
 use std::env;
@@ -441,7 +442,10 @@ fn for_each_region_constraint<'tcx>(
         let subject = match req.subject {
             ClosureOutlivesSubject::Region(subject) => format!("{subject:?}"),
             ClosureOutlivesSubject::Ty(ty) => {
-                format!("{:?}", ty.instantiate(tcx, |vid| ty::Region::new_var(tcx, vid)))
+                with_no_trimmed_paths!(format!(
+                    "{}",
+                    ty.instantiate(tcx, |vid| ty::Region::new_var(tcx, vid))
+                ))
             }
         };
         with_msg(format!("where {}: {:?}", subject, req.outlived_free_region,))?;

compiler/rustc_borrowck/src/universal_regions.rs

@@ -21,6 +21,7 @@ use rustc_hir::BodyOwnerKind;
 use rustc_index::IndexVec;
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::ty::fold::TypeFoldable;
+use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, InlineConstArgs, InlineConstArgsParts, RegionVid, Ty, TyCtxt};
 use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_span::symbol::{kw, sym};
@@ -332,10 +333,16 @@ impl<'tcx> UniversalRegions<'tcx> {
     pub(crate) fn annotate(&self, tcx: TyCtxt<'tcx>, err: &mut Diagnostic) {
         match self.defining_ty {
             DefiningTy::Closure(def_id, args) => {
+                let v = with_no_trimmed_paths!(
+                    args[tcx.generics_of(def_id).parent_count..]
+                        .iter()
+                        .map(|arg| arg.to_string())
+                        .collect::<Vec<_>>()
+                );
                 err.note(format!(
-                    "defining type: {} with closure args {:#?}",
+                    "defining type: {} with closure args [\n    {},\n]",
                     tcx.def_path_str_with_args(def_id, args),
-                    &args[tcx.generics_of(def_id).parent_count..],
+                    v.join(",\n    "),
                 ));
 
                 // FIXME: It'd be nice to print the late-bound regions
@@ -348,10 +355,16 @@ impl<'tcx> UniversalRegions<'tcx> {
                 });
             }
             DefiningTy::Generator(def_id, args, _) => {
+                let v = with_no_trimmed_paths!(
+                    args[tcx.generics_of(def_id).parent_count..]
+                        .iter()
+                        .map(|arg| arg.to_string())
+                        .collect::<Vec<_>>()
+                );
                 err.note(format!(
-                    "defining type: {} with generator args {:#?}",
+                    "defining type: {} with generator args [\n    {},\n]",
                     tcx.def_path_str_with_args(def_id, args),
-                    &args[tcx.generics_of(def_id).parent_count..],
+                    v.join(",\n    "),
                 ));
 
                 // FIXME: As above, we'd like to print out the region

compiler/rustc_middle/src/infer/canonical.rs

@@ -27,6 +27,7 @@ use crate::ty::GenericArg;
 use crate::ty::{self, BoundVar, List, Region, Ty, TyCtxt};
 use rustc_macros::HashStable;
 use smallvec::SmallVec;
+use std::fmt::Display;
 use std::ops::Index;
 
 /// A "canonicalized" type `V` is one where all free inference
@@ -40,6 +41,16 @@ pub struct Canonical<'tcx, V> {
     pub variables: CanonicalVarInfos<'tcx>,
 }
 
+impl<'tcx, V: Display> std::fmt::Display for Canonical<'tcx, V> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "Canonical {{ value: {}, max_universe: {:?}, variables: {:?} }}",
+            self.value, self.max_universe, self.variables
+        )
+    }
+}
+
 pub type CanonicalVarInfos<'tcx> = &'tcx List<CanonicalVarInfo<'tcx>>;
 
 impl<'tcx> ty::TypeFoldable<TyCtxt<'tcx>> for CanonicalVarInfos<'tcx> {

compiler/rustc_middle/src/mir/mod.rs

@@ -8,6 +8,7 @@ use crate::mir::interpret::{
 use crate::mir::visit::MirVisitable;
 use crate::ty::codec::{TyDecoder, TyEncoder};
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable};
+use crate::ty::print::with_no_trimmed_paths;
 use crate::ty::print::{FmtPrinter, Printer};
 use crate::ty::visit::TypeVisitableExt;
 use crate::ty::{self, List, Ty, TyCtxt};
@@ -1787,7 +1788,7 @@ fn post_fmt_projection(projection: &[PlaceElem<'_>], fmt: &mut Formatter<'_>) ->
                 write!(fmt, ")")?;
             }
             ProjectionElem::Field(field, ty) => {
-                write!(fmt, ".{:?}: {:?})", field.index(), ty)?;
+                with_no_trimmed_paths!(write!(fmt, ".{:?}: {})", field.index(), ty)?);
             }
             ProjectionElem::Index(ref index) => {
                 write!(fmt, "[{index:?}]")?;
@@ -2070,19 +2071,22 @@ impl<'tcx> Debug for Rvalue<'tcx> {
             }
             Len(ref a) => write!(fmt, "Len({a:?})"),
             Cast(ref kind, ref place, ref ty) => {
-                write!(fmt, "{place:?} as {ty:?} ({kind:?})")
+                with_no_trimmed_paths!(write!(fmt, "{place:?} as {ty} ({kind:?})"))
             }
             BinaryOp(ref op, box (ref a, ref b)) => write!(fmt, "{op:?}({a:?}, {b:?})"),
             CheckedBinaryOp(ref op, box (ref a, ref b)) => {
                 write!(fmt, "Checked{op:?}({a:?}, {b:?})")
             }
             UnaryOp(ref op, ref a) => write!(fmt, "{op:?}({a:?})"),
             Discriminant(ref place) => write!(fmt, "discriminant({place:?})"),
-            NullaryOp(ref op, ref t) => match op {
-                NullOp::SizeOf => write!(fmt, "SizeOf({t:?})"),
-                NullOp::AlignOf => write!(fmt, "AlignOf({t:?})"),
-                NullOp::OffsetOf(fields) => write!(fmt, "OffsetOf({t:?}, {fields:?})"),
-            },
+            NullaryOp(ref op, ref t) => {
+                let t = with_no_trimmed_paths!(format!("{}", t));
+                match op {
+                    NullOp::SizeOf => write!(fmt, "SizeOf({t})"),
+                    NullOp::AlignOf => write!(fmt, "AlignOf({t})"),
+                    NullOp::OffsetOf(fields) => write!(fmt, "OffsetOf({t}, {fields:?})"),
+                }
+            }
             ThreadLocalRef(did) => ty::tls::with(|tcx| {
                 let muta = tcx.static_mutability(did).unwrap().prefix_str();
                 write!(fmt, "&/*tls*/ {}{}", muta, tcx.def_path_str(did))
@@ -2218,7 +2222,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
             }
 
             ShallowInitBox(ref place, ref ty) => {
-                write!(fmt, "ShallowInitBox({place:?}, {ty:?})")
+                with_no_trimmed_paths!(write!(fmt, "ShallowInitBox({place:?}, {ty})"))
             }
         }
     }

compiler/rustc_middle/src/mir/pretty.rs

@@ -583,8 +583,10 @@ fn write_scope_tree(
 
         let mut_str = local_decl.mutability.prefix_str();
 
-        let mut indented_decl =
-            format!("{0:1$}let {2}{3:?}: {4:?}", INDENT, indent, mut_str, local, local_decl.ty);
+        let mut indented_decl = ty::print::with_no_trimmed_paths!(format!(
+            "{0:1$}let {2}{3:?}: {4}",
+            INDENT, indent, mut_str, local, local_decl.ty
+        ));
         if let Some(user_ty) = &local_decl.user_ty {
             for user_ty in user_ty.projections() {
                 write!(indented_decl, " as {user_ty:?}").unwrap();
@@ -1058,11 +1060,11 @@ fn write_user_type_annotations(
     for (index, annotation) in body.user_type_annotations.iter_enumerated() {
         writeln!(
             w,
-            "| {:?}: user_ty: {:?}, span: {}, inferred_ty: {:?}",
+            "| {:?}: user_ty: {}, span: {}, inferred_ty: {}",
             index.index(),
             annotation.user_ty,
             tcx.sess.source_map().span_to_embeddable_string(annotation.span),
-            annotation.inferred_ty,
+            with_no_trimmed_paths!(format!("{}", annotation.inferred_ty)),
         )?;
     }
     if !body.user_type_annotations.is_empty() {

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -760,9 +760,13 @@ pub trait PrettyPrinter<'tcx>:
                 // only affect certain debug messages (e.g. messages printed
                 // from `rustc_middle::ty` during the computation of `tcx.predicates_of`),
                 // and should have no effect on any compiler output.
+                // [Untrue! It shows up in the output of
+                // tests/ui/nll/ty-outlives/impl-trait-captures.rs, for
+                // example.]
                 if self.should_print_verbose() {
                     // FIXME(eddyb) print this with `print_def_path`.
-                    p!(write("Opaque({:?}, {:?})", def_id, args));
+                    let v = args.iter().map(|arg| arg.to_string()).collect::<Vec<_>>();
+                    p!(write("Opaque({:?}, [{}])", def_id, v.join(", ")));
                     return Ok(self);
                 }
 
@@ -894,7 +898,8 @@ pub trait PrettyPrinter<'tcx>:
                     p!(print_def_path(did, args));
                     if !args.as_closure().is_valid() {
                         p!(" closure_args=(unavailable)");
-                        p!(write(" args={:?}", args));
+                        let v = args.iter().map(|arg| arg.to_string()).collect::<Vec<_>>();
+                        p!(write(" args=[{}]", v.join(", ")));
                     } else {
                         p!(" closure_kind_ty=", print(args.as_closure().kind_ty()));
                         p!(

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -154,7 +154,7 @@ impl<'tcx> ty::DebugWithInfcx<TyCtxt<'tcx>> for Ty<'tcx> {
 }
 impl<'tcx> fmt::Debug for Ty<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        with_no_trimmed_paths!(fmt::Display::fmt(self, f))
+        with_no_trimmed_paths!(fmt::Debug::fmt(self.kind(), f))
     }
 }
 

compiler/rustc_middle/src/ty/typeck_results.rs

@@ -722,3 +722,14 @@ pub enum UserType<'tcx> {
     /// given substitutions applied.
     TypeOf(DefId, UserArgs<'tcx>),
 }
+
+impl<'tcx> std::fmt::Display for UserType<'tcx> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Ty(arg0) => {
+                ty::print::with_no_trimmed_paths!(write!(f, "Ty({})", arg0))
+            }
+            Self::TypeOf(arg0, arg1) => write!(f, "TypeOf({:?}, {:?})", arg0, arg1),
+        }
+    }
+}

compiler/rustc_passes/src/abi_test.rs

@@ -63,6 +63,7 @@ fn dump_abi_of(tcx: TyCtxt<'_>, item_def_id: DefId, attr: &Attribute) {
                         tcx.sess.emit_err(AbiOf {
                             span: tcx.def_span(item_def_id),
                             fn_name,
+                            // FIXME: using the `Debug` impl here isn't ideal.
                             fn_abi: format!("{:#?}", abi),
                         });
                     }

compiler/rustc_passes/src/layout_test.rs

@@ -76,6 +76,7 @@ fn dump_layout_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId, attr: &Attribute) {
                                 ty,
                             )
                         );
+                        // FIXME: using the `Debug` impl here isn't ideal.
                         let ty_layout = format!("{:#?}", *ty_layout);
                         tcx.sess.emit_err(LayoutOf {
                             span: tcx.def_span(item_def_id.to_def_id()),

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1792,7 +1792,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         );
                     } else {
                         err.note(format!(
-                            "`{}` is implemented for `{:?}`, but not for `{:?}`",
+                            "`{}` is implemented for `{}`, but not for `{}`",
                             trait_pred.print_modifiers_and_trait_path(),
                             suggested_ty,
                             trait_pred.skip_binder().self_ty(),

compiler/rustc_ty_utils/src/layout.rs

@@ -7,6 +7,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::layout::{
     IntegerExt, LayoutCx, LayoutError, LayoutOf, TyAndLayout, MAX_SIMD_LANES,
 };
+use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{
     self, AdtDef, EarlyBinder, GenericArgsRef, ReprOptions, Ty, TyCtxt, TypeVisitableExt,
 };
@@ -937,7 +938,7 @@ fn record_layout_for_printing_outlined<'tcx>(
 
     // (delay format until we actually need it)
     let record = |kind, packed, opt_discr_size, variants| {
-        let type_desc = format!("{:?}", layout.ty);
+        let type_desc = with_no_trimmed_paths!(format!("{}", layout.ty));
         cx.tcx.sess.code_stats.record_type_size(
             kind,
             type_desc,

tests/mir-opt/building/async_await.b-{closure#0}.generator_resume.0.mir

@@ -2,15 +2,29 @@
 /* generator_layout = GeneratorLayout {
     field_tys: {
         _0: GeneratorSavedTy {
-            ty: impl std::future::Future<Output = ()>,
+            ty: Alias(
+                Opaque,
+                AliasTy {
+                    args: [
+                    ],
+                    def_id: DefId(0:7 ~ async_await[ccf8]::a::{opaque#0}),
+                },
+            ),
             source_info: SourceInfo {
                 span: $DIR/async_await.rs:15:9: 15:14 (#8),
                 scope: scope[0],
             },
             ignore_for_traits: false,
         },
         _1: GeneratorSavedTy {
-            ty: impl std::future::Future<Output = ()>,
+            ty: Alias(
+                Opaque,
+                AliasTy {
+                    args: [
+                    ],
+                    def_id: DefId(0:7 ~ async_await[ccf8]::a::{opaque#0}),
+                },
+            ),
             source_info: SourceInfo {
                 span: $DIR/async_await.rs:16:9: 16:14 (#10),
                 scope: scope[0],

tests/mir-opt/generator_drop_cleanup.main-{closure#0}.generator_drop.0.panic-abort.mir

@@ -2,7 +2,11 @@
 /* generator_layout = GeneratorLayout {
     field_tys: {
         _0: GeneratorSavedTy {
-            ty: std::string::String,
+            ty: Adt(
+                std::string::String,
+                [
+                ],
+            ),
             source_info: SourceInfo {
                 span: $DIR/generator_drop_cleanup.rs:11:13: 11:15 (#0),
                 scope: scope[0],

tests/mir-opt/generator_drop_cleanup.main-{closure#0}.generator_drop.0.panic-unwind.mir

@@ -2,7 +2,11 @@
 /* generator_layout = GeneratorLayout {
     field_tys: {
         _0: GeneratorSavedTy {
-            ty: std::string::String,
+            ty: Adt(
+                std::string::String,
+                [
+                ],
+            ),
             source_info: SourceInfo {
                 span: $DIR/generator_drop_cleanup.rs:11:13: 11:15 (#0),
                 scope: scope[0],

tests/mir-opt/generator_tiny.main-{closure#0}.generator_resume.0.mir

@@ -2,7 +2,11 @@
 /* generator_layout = GeneratorLayout {
     field_tys: {
         _0: GeneratorSavedTy {
-            ty: HasDrop,
+            ty: Adt(
+                HasDrop,
+                [
+                ],
+            ),
             source_info: SourceInfo {
                 span: $DIR/generator_tiny.rs:20:13: 20:15 (#0),
                 scope: scope[0],

tests/mir-opt/issue_99325.main.built.after.mir

@@ -1,8 +1,8 @@
 // MIR for `main` after built
 
 | User Type Annotations
-| 0: user_ty: Canonical { value: TypeOf(DefId(0:3 ~ issue_99325[22bb]::function_with_bytes), UserArgs { args: [Const { ty: &'static [u8; 4], kind: Branch([Leaf(0x41), Leaf(0x41), Leaf(0x41), Leaf(0x41)]) }], user_self_ty: None }), max_universe: U0, variables: [] }, span: $DIR/issue_99325.rs:10:16: 10:46, inferred_ty: fn() -> &'static [u8] {function_with_bytes::<&*b"AAAA">}
-| 1: user_ty: Canonical { value: TypeOf(DefId(0:3 ~ issue_99325[22bb]::function_with_bytes), UserArgs { args: [Const { ty: &'static [u8; 4], kind: UnevaluatedConst { def: DefId(0:8 ~ issue_99325[22bb]::main::{constant#1}), args: [] } }], user_self_ty: None }), max_universe: U0, variables: [] }, span: $DIR/issue_99325.rs:11:16: 11:68, inferred_ty: fn() -> &'static [u8] {function_with_bytes::<&*b"AAAA">}
+| 0: user_ty: Canonical { value: TypeOf(DefId(0:3 ~ issue_99325[22bb]::function_with_bytes), UserArgs { args: [Const { ty: &ReStatic [u8; Const { ty: usize, kind: Leaf(0x0000000000000004) }], kind: Branch([Leaf(0x41), Leaf(0x41), Leaf(0x41), Leaf(0x41)]) }], user_self_ty: None }), max_universe: U0, variables: [] }, span: $DIR/issue_99325.rs:10:16: 10:46, inferred_ty: fn() -> &'static [u8] {function_with_bytes::<&*b"AAAA">}
+| 1: user_ty: Canonical { value: TypeOf(DefId(0:3 ~ issue_99325[22bb]::function_with_bytes), UserArgs { args: [Const { ty: &ReStatic [u8; Const { ty: usize, kind: Leaf(0x0000000000000004) }], kind: UnevaluatedConst { def: DefId(0:8 ~ issue_99325[22bb]::main::{constant#1}), args: [] } }], user_self_ty: None }), max_universe: U0, variables: [] }, span: $DIR/issue_99325.rs:11:16: 11:68, inferred_ty: fn() -> &'static [u8] {function_with_bytes::<&*b"AAAA">}
 |
 fn main() -> () {
     let mut _0: ();

tests/ui/abi/debug.stderr

@@ -96,7 +96,7 @@ error: fn_abi_of_instance(test_generic) = FnAbi {
            args: [
                ArgAbi {
                    layout: TyAndLayout {
-                       ty: *const T,
+                       ty: *const T/#0,
                        layout: Layout {
                            size: $SOME_SIZE,
                            align: AbiAndPrefAlign {
@@ -172,7 +172,7 @@ error: fn_abi_of_instance(assoc_test) = FnAbi {
            args: [
                ArgAbi {
                    layout: TyAndLayout {
-                       ty: &S,
+                       ty: &ReErased Adt(S, []),
                        layout: Layout {
                            size: $SOME_SIZE,
                            align: AbiAndPrefAlign {

tests/ui/async-await/async-is-unwindsafe.stderr

@@ -15,7 +15,7 @@ LL | |     });
    |       within this `[async block@$DIR/async-is-unwindsafe.rs:12:19: 29:6]`
    |
    = help: within `[async block@$DIR/async-is-unwindsafe.rs:12:19: 29:6]`, the trait `UnwindSafe` is not implemented for `&mut Context<'_>`
-   = note: `UnwindSafe` is implemented for `&std::task::Context<'_>`, but not for `&mut std::task::Context<'_>`
+   = note: `UnwindSafe` is implemented for `&Context<'_>`, but not for `&mut Context<'_>`
 note: future does not implement `UnwindSafe` as this value is used across an await
   --> $DIR/async-is-unwindsafe.rs:25:18
    |