middle: const {Meta,Pointee}Sized in opaques

davidtwco · davidtwco · commit d39668f37c2b · 2025-04-01T09:27:29.000Z
These traits are now const and that needs to be reflected in their
printing in opaques.
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1064,10 +1064,12 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         let mut fn_traits = FxIndexMap::default();
         let mut lifetimes = SmallVec::<[ty::Region<'tcx>; 1]>::new();
 
-        let mut has_sized_bound = false;
-        let mut has_negative_sized_bound = false;
-        let mut has_meta_sized_bound = false;
-        let mut has_pointee_sized_bound = false;
+        let mut has_sized_pred = false;
+        let mut has_const_sized_pred = false;
+        let mut has_negative_sized_pred = false;
+        let mut has_meta_sized_pred = false;
+        let mut has_const_meta_sized_pred = false;
+        let mut has_pointee_sized_pred = false;
 
         for (predicate, _) in bounds.iter_instantiated_copied(tcx, args) {
             let bound_predicate = predicate.kind();
@@ -1079,17 +1081,17 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     if tcx.is_lang_item(pred.def_id(), LangItem::Sized) {
                         match pred.polarity {
                             ty::PredicatePolarity::Positive => {
-                                has_sized_bound = true;
+                                has_sized_pred = true;
                                 continue;
                             }
-                            ty::PredicatePolarity::Negative => has_negative_sized_bound = true,
+                            ty::PredicatePolarity::Negative => has_negative_sized_pred = true,
                         }
                     } else if tcx.is_lang_item(pred.def_id(), LangItem::MetaSized) {
-                        has_meta_sized_bound = true;
+                        has_meta_sized_pred = true;
                         continue;
                     } else if tcx.is_lang_item(pred.def_id(), LangItem::PointeeSized) {
                         // Unexpected - `PointeeSized` is the absence of bounds.
-                        has_pointee_sized_bound = true;
+                        has_pointee_sized_pred = true;
                         continue;
                     }
 
@@ -1117,6 +1119,13 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 ty::ClauseKind::TypeOutlives(outlives) => {
                     lifetimes.push(outlives.1);
                 }
+                ty::ClauseKind::HostEffect(pred) => {
+                    if tcx.is_lang_item(pred.def_id(), LangItem::Sized) {
+                        has_const_sized_pred = true;
+                    } else if tcx.is_lang_item(pred.def_id(), LangItem::MetaSized) {
+                        has_const_meta_sized_pred = true;
+                    }
+                }
                 _ => {}
             }
         }
@@ -1125,7 +1134,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
 
         let mut first = true;
         // Insert parenthesis around (Fn(A, B) -> C) if the opaque ty has more than one other trait
-        let paren_needed = fn_traits.len() > 1 || traits.len() > 0 || !has_sized_bound;
+        let paren_needed = fn_traits.len() > 1 || traits.len() > 0 || !has_sized_pred;
 
         for ((bound_args_and_self_ty, is_async), entry) in fn_traits {
             write!(self, "{}", if first { "" } else { " + " })?;
@@ -1260,26 +1269,31 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         }
 
         let using_sized_hierarchy = self.tcx().features().sized_hierarchy();
-        let add_sized = has_sized_bound && (first || has_negative_sized_bound);
+        let add_sized = has_sized_pred && (first || has_negative_sized_pred);
         let add_maybe_sized =
-            has_meta_sized_bound && !has_negative_sized_bound && !using_sized_hierarchy;
+            has_meta_sized_pred && !has_negative_sized_pred && !using_sized_hierarchy;
         // Set `has_pointee_sized_bound` if there were no `Sized` or `MetaSized` bounds.
-        has_pointee_sized_bound = has_pointee_sized_bound
-            || (!has_sized_bound && !has_meta_sized_bound && !has_negative_sized_bound);
+        has_pointee_sized_pred = has_pointee_sized_pred
+            || (!has_sized_pred && !has_meta_sized_pred && !has_negative_sized_pred);
         if add_sized || add_maybe_sized {
             if !first {
                 write!(self, " + ")?;
             }
             if add_maybe_sized {
                 write!(self, "?")?;
+            } else if has_const_sized_pred && using_sized_hierarchy {
+                write!(self, "const ")?;
             }
             write!(self, "Sized")?;
-        } else if has_meta_sized_bound && using_sized_hierarchy {
+        } else if has_meta_sized_pred && using_sized_hierarchy {
             if !first {
                 write!(self, " + ")?;
             }
+            if has_const_meta_sized_pred && using_sized_hierarchy {
+                write!(self, "const ")?;
+            }
             write!(self, "MetaSized")?;
-        } else if has_pointee_sized_bound && using_sized_hierarchy {
+        } else if has_pointee_sized_pred && using_sized_hierarchy {
             if !first {
                 write!(self, " + ")?;
             }
diff --git a/tests/ui/sized-hierarchy/pretty-print-opaque.rs b/tests/ui/sized-hierarchy/pretty-print-opaque.rs
@@ -1,5 +1,5 @@
 //@ compile-flags: --crate-type=lib
-#![feature(sized_hierarchy)]
+#![feature(const_trait_impl, sized_hierarchy)]
 
 use std::marker::{MetaSized, PointeeSized};
 
@@ -14,11 +14,19 @@ pub fn sized() -> Box<impl Tr + Sized> {
     Box::new(1u32)
 }
 
+pub fn const_sized() -> Box<impl Tr + const Sized> {
+    if true {
+        let x = const_sized();
+        let y: Box<dyn Tr> = x;
+    }
+    Box::new(1u32)
+}
+
 pub fn neg_sized() -> Box<impl Tr + ?Sized> {
     if true {
         let x = neg_sized();
         let y: Box<dyn Tr> = x;
-//~^ ERROR: the size for values of type `impl Tr + MetaSized` cannot be known
+//~^ ERROR: the size for values of type `impl Tr + const MetaSized` cannot be known
     }
     Box::new(1u32)
 }
@@ -32,6 +40,15 @@ pub fn metasized() -> Box<impl Tr + MetaSized> {
     Box::new(1u32)
 }
 
+pub fn const_metasized() -> Box<impl Tr + const MetaSized> {
+    if true {
+        let x = const_metasized();
+        let y: Box<dyn Tr> = x;
+//~^ ERROR: the size for values of type `impl Tr + const MetaSized` cannot be known
+    }
+    Box::new(1u32)
+}
+
 pub fn pointeesized() -> Box<impl Tr + PointeeSized> {
 //~^ ERROR: the size for values of type `impl Tr + PointeeSized` cannot be known
     if true {
@@ -42,4 +59,3 @@ pub fn pointeesized() -> Box<impl Tr + PointeeSized> {
     }
     Box::new(1u32)
 }
-
diff --git a/tests/ui/sized-hierarchy/pretty-print-opaque.stderr b/tests/ui/sized-hierarchy/pretty-print-opaque.stderr
@@ -1,5 +1,5 @@
 error[E0277]: the size for values of type `impl Tr + PointeeSized` cannot be known
-  --> $DIR/pretty-print-opaque.rs:35:26
+  --> $DIR/pretty-print-opaque.rs:52:26
    |
 LL | pub fn pointeesized() -> Box<impl Tr + PointeeSized> {
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a known size
@@ -8,26 +8,35 @@ LL | pub fn pointeesized() -> Box<impl Tr + PointeeSized> {
 note: required by a bound in `Box`
   --> $SRC_DIR/alloc/src/boxed.rs:LL:COL
 
-error[E0277]: the size for values of type `impl Tr + MetaSized` cannot be known at compilation time
-  --> $DIR/pretty-print-opaque.rs:20:30
+error[E0277]: the size for values of type `impl Tr + const MetaSized` cannot be known at compilation time
+  --> $DIR/pretty-print-opaque.rs:28:30
    |
 LL |         let y: Box<dyn Tr> = x;
    |                              ^ doesn't have a size known at compile-time
    |
-   = help: the trait `Sized` is not implemented for `impl Tr + MetaSized`
-   = note: required for the cast from `Box<impl Tr + MetaSized>` to `Box<dyn Tr>`
+   = help: the trait `Sized` is not implemented for `impl Tr + const MetaSized`
+   = note: required for the cast from `Box<impl Tr + const MetaSized>` to `Box<dyn Tr>`
 
 error[E0277]: the size for values of type `impl Tr + MetaSized` cannot be known at compilation time
-  --> $DIR/pretty-print-opaque.rs:29:30
+  --> $DIR/pretty-print-opaque.rs:37:30
    |
 LL |         let y: Box<dyn Tr> = x;
    |                              ^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `impl Tr + MetaSized`
    = note: required for the cast from `Box<impl Tr + MetaSized>` to `Box<dyn Tr>`
 
+error[E0277]: the size for values of type `impl Tr + const MetaSized` cannot be known at compilation time
+  --> $DIR/pretty-print-opaque.rs:46:30
+   |
+LL |         let y: Box<dyn Tr> = x;
+   |                              ^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `impl Tr + const MetaSized`
+   = note: required for the cast from `Box<impl Tr + const MetaSized>` to `Box<dyn Tr>`
+
 error[E0277]: the size for values of type `impl Tr + PointeeSized` cannot be known
-  --> $DIR/pretty-print-opaque.rs:38:17
+  --> $DIR/pretty-print-opaque.rs:55:17
    |
 LL |         let x = pointeesized();
    |                 ^^^^^^^^^^^^^^ doesn't have a known size
@@ -37,14 +46,14 @@ note: required by a bound in `Box`
   --> $SRC_DIR/alloc/src/boxed.rs:LL:COL
 
 error[E0277]: the size for values of type `impl Tr + PointeeSized` cannot be known at compilation time
-  --> $DIR/pretty-print-opaque.rs:40:30
+  --> $DIR/pretty-print-opaque.rs:57:30
    |
 LL |         let y: Box<dyn Tr> = x;
    |                              ^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `impl Tr + PointeeSized`
    = note: required for the cast from `Box<impl Tr + PointeeSized>` to `Box<dyn Tr>`
 
-error: aborting due to 5 previous errors
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
