Auto merge of #118788 - compiler-errors:const-pretty, r=fee1-dead

Don't print host effect param in pretty `path_generic_args`

Make `own_args_no_defaults` pass back the `GenericParamDef`, so that we can pass both the args *and* param definitions into `path_generic_args`. That allows us to use the `GenericParamDef` to filter out effect params.

This allows us to filter out the host param regardless of whether it's `sym::host` or `true`/`false`.

This also renames a couple of `const_effect_param` -> `host_effect_param`, and restores `~const` pretty printing to `TraitPredPrintModifiersAndPath`.

cc #118785
r? `@fee1-dead` cc `@oli-obk`

compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs

@@ -172,7 +172,7 @@ impl Qualif for NeedsNonConstDrop {
                 destruct_def_id,
                 [
                     ty::GenericArg::from(ty),
-                    ty::GenericArg::from(cx.tcx.expected_const_effect_param_for_body(cx.def_id())),
+                    ty::GenericArg::from(cx.tcx.expected_host_effect_param_for_body(cx.def_id())),
                 ],
             ),
         );

compiler/rustc_const_eval/src/util/type_name.rs

@@ -120,6 +120,7 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
+        _params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError> {
         print_prefix(self)?;
         let args =

compiler/rustc_hir_typeck/src/callee.rs

@@ -780,7 +780,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let generics = tcx.generics_of(callee_did);
         let Some(host_effect_index) = generics.host_effect_index else { return };
 
-        let effect = tcx.expected_const_effect_param_for_body(self.body_id);
+        let effect = tcx.expected_host_effect_param_for_body(self.body_id);
 
         trace!(?effect, ?generics, ?callee_args);
 

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -641,6 +641,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 &mut self,
                 print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
                 _args: &[GenericArg<'tcx>],
+                _params: &[ty::GenericParamDef],
             ) -> Result<(), PrintError> {
                 print_prefix(self)
             }
@@ -1236,9 +1237,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             (&ty::Adt(def1, sub1), &ty::Adt(def2, sub2)) => {
                 let did1 = def1.did();
                 let did2 = def2.did();
-                let sub_no_defaults_1 =
+                let (sub_no_defaults_1, _) =
                     self.tcx.generics_of(did1).own_args_no_defaults(self.tcx, sub1);
-                let sub_no_defaults_2 =
+                let (sub_no_defaults_2, _) =
                     self.tcx.generics_of(did2).own_args_no_defaults(self.tcx, sub2);
                 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
                 let path1 = self.tcx.def_path_str(did1);

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -757,6 +757,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                             .tcx
                             .generics_of(def.did())
                             .own_args_no_defaults(self.tcx, args)
+                            .0
                             .iter()
                             .map(|&arg| self.arg_cost(arg))
                             .sum::<usize>()
@@ -1185,7 +1186,7 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
                 }
                 let args = self.infcx.resolve_vars_if_possible(args);
                 let generic_args =
-                    &generics.own_args_no_defaults(tcx, args)[generics.own_counts().lifetimes..];
+                    &generics.own_args_no_defaults(tcx, args).0[generics.own_counts().lifetimes..];
                 let span = match expr.kind {
                     ExprKind::MethodCall(path, ..) => path.ident.span,
                     _ => expr.span,

compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs

@@ -116,7 +116,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             // FIXME: extract this logic for use in other diagnostics.
                             let (trait_ref, assoc_args) = proj.trait_ref_and_own_args(tcx);
                             let item_name = tcx.item_name(proj.def_id);
-                            let item_args = self.format_generic_args(assoc_args);
+                            let item_args = self.format_generic_args(proj.def_id, assoc_args);
 
                             // Here, we try to see if there's an existing
                             // trait implementation that matches the one that
@@ -775,7 +775,7 @@ fn foo(&self) -> Self::T { String::new() }
                 let span = Span::new(pos, pos, span.ctxt(), span.parent());
                 (span, format!(", {} = {}", assoc.ident(tcx), ty))
             } else {
-                let item_args = self.format_generic_args(assoc_args);
+                let item_args = self.format_generic_args(assoc.def_id, assoc_args);
                 (span.shrink_to_hi(), format!("<{}{} = {}>", assoc.ident(tcx), item_args, ty))
             };
             diag.span_suggestion_verbose(span, msg(), sugg, MaybeIncorrect);
@@ -784,9 +784,13 @@ fn foo(&self) -> Self::T { String::new() }
         false
     }
 
-    pub fn format_generic_args(&self, args: &[ty::GenericArg<'tcx>]) -> String {
+    pub fn format_generic_args(
+        &self,
+        assoc_def_id: DefId,
+        args: &[ty::GenericArg<'tcx>],
+    ) -> String {
         FmtPrinter::print_string(self.tcx, hir::def::Namespace::TypeNS, |cx| {
-            cx.path_generic_args(|_| Ok(()), args)
+            cx.path_generic_args(|_| Ok(()), args, &self.infcx.tcx.generics_of(assoc_def_id).params)
         })
         .expect("could not write to `String`.")
     }

compiler/rustc_lint/src/context.rs

@@ -1285,6 +1285,7 @@ impl<'tcx> LateContext<'tcx> {
                 &mut self,
                 print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
                 _args: &[GenericArg<'tcx>],
+                _params: &[ty::GenericParamDef],
             ) -> Result<(), PrintError> {
                 print_prefix(self)
             }

compiler/rustc_middle/src/ty/generics.rs

@@ -320,9 +320,11 @@ impl<'tcx> Generics {
         &'tcx self,
         tcx: TyCtxt<'tcx>,
         args: &'tcx [ty::GenericArg<'tcx>],
-    ) -> &'tcx [ty::GenericArg<'tcx>] {
-        let mut own_params = self.parent_count..self.count();
+    ) -> (&'tcx [ty::GenericArg<'tcx>], &'tcx [ty::GenericParamDef]) {
+        let mut own_args = self.parent_count..self.count();
+        let mut own_params = 0..self.params.len();
         if self.has_self && self.parent.is_none() {
+            own_args.start = 1;
             own_params.start = 1;
         }
 
@@ -332,7 +334,7 @@ impl<'tcx> Generics {
         // of semantic equivalence. While not ideal, that's
         // good enough for now as this should only be used
         // for diagnostics anyways.
-        own_params.end -= self
+        let num_default_params = self
             .params
             .iter()
             .rev()
@@ -342,8 +344,10 @@ impl<'tcx> Generics {
                 })
             })
             .count();
+        own_params.end -= num_default_params;
+        own_args.end -= num_default_params;
 
-        &args[own_params]
+        (&args[own_args], &self.params[own_params])
     }
 
     /// Returns the args corresponding to the generic parameters of this item, excluding `Self`.

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

@@ -83,6 +83,7 @@ pub trait Printer<'tcx>: Sized {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
+        params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError>;
 
     // Defaults (should not be overridden):
@@ -141,10 +142,12 @@ pub trait Printer<'tcx>: Sized {
                         // on top of the same path, but without its own generics.
                         _ => {
                             if !generics.params.is_empty() && args.len() >= generics.count() {
-                                let args = generics.own_args_no_defaults(self.tcx(), args);
+                                let (args, params) =
+                                    generics.own_args_no_defaults(self.tcx(), args);
                                 return self.path_generic_args(
                                     |cx| cx.print_def_path(def_id, parent_args),
                                     args,
+                                    params,
                                 );
                             }
                         }

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

@@ -19,7 +19,6 @@ use rustc_hir::LangItem;
 use rustc_session::config::TrimmedDefPaths;
 use rustc_session::cstore::{ExternCrate, ExternCrateSource};
 use rustc_session::Limit;
-use rustc_span::sym;
 use rustc_span::symbol::{kw, Ident, Symbol};
 use rustc_span::FileNameDisplayPreference;
 use rustc_target::abi::Size;
@@ -967,7 +966,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 define_scoped_cx!(cx);
                 // Get the (single) generic ty (the args) of this FnOnce trait ref.
                 let generics = tcx.generics_of(trait_ref.def_id);
-                let own_args = generics.own_args_no_defaults(tcx, trait_ref.args);
+                let (own_args, _) = generics.own_args_no_defaults(tcx, trait_ref.args);
 
                 match (entry.return_ty, own_args[0].expect_ty()) {
                     // We can only print `impl Fn() -> ()` if we have a tuple of args and we recorded
@@ -1033,7 +1032,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 p!(print(trait_ref.print_only_trait_name()));
 
                 let generics = tcx.generics_of(trait_ref.def_id);
-                let own_args = generics.own_args_no_defaults(tcx, trait_ref.args);
+                let (own_args, _) = generics.own_args_no_defaults(tcx, trait_ref.args);
 
                 if !own_args.is_empty() || !assoc_items.is_empty() {
                     let mut first = true;
@@ -1185,6 +1184,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 )
             },
             &alias_ty.args[1..],
+            &self.tcx().generics_of(alias_ty.def_id).params,
         )
     }
 
@@ -1233,7 +1233,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     let dummy_cx = Ty::new_fresh(cx.tcx(), 0);
                     let principal = principal.with_self_ty(cx.tcx(), dummy_cx);
 
-                    let args = cx
+                    let (args, _) = cx
                         .tcx()
                         .generics_of(principal.def_id)
                         .own_args_no_defaults(cx.tcx(), principal.args);
@@ -2031,40 +2031,26 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
+        params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError> {
         print_prefix(self)?;
 
         let tcx = self.tcx;
-
-        let args = args.iter().copied();
-
-        let args: Vec<_> = if !tcx.sess.verbose() {
-            // skip host param as those are printed as `~const`
-            args.filter(|arg| match arg.unpack() {
-                // FIXME(effects) there should be a better way than just matching the name
-                GenericArgKind::Const(c)
-                    if tcx.features().effects
-                        && matches!(
-                            c.kind(),
-                            ty::ConstKind::Param(ty::ParamConst { name: sym::host, .. })
-                        ) =>
-                {
-                    false
-                }
-                _ => true,
-            })
-            .collect()
-        } else {
+        let verbose = tcx.sess.verbose();
+        let mut args = args
+            .iter()
+            .copied()
+            .zip(params)
             // If -Zverbose is passed, we should print the host parameter instead
             // of eating it.
-            args.collect()
-        };
+            .filter(|(_, param)| verbose || !param.is_host_effect())
+            .peekable();
 
-        if !args.is_empty() {
+        if args.peek().is_some() {
             if self.in_value {
                 write!(self, "::")?;
             }
-            self.generic_delimiters(|cx| cx.comma_sep(args.into_iter()))
+            self.generic_delimiters(|cx| cx.comma_sep(args.map(|(arg, _)| arg)))
         } else {
             Ok(())
         }
@@ -2894,11 +2880,15 @@ define_print_and_forward_display! {
     }
 
     TraitPredPrintModifiersAndPath<'tcx> {
-        // FIXME(effects) print `~const` here
+        if let Some(idx) = cx.tcx().generics_of(self.0.trait_ref.def_id).host_effect_index
+        {
+            if self.0.trait_ref.args.const_at(idx) != cx.tcx().consts.true_ {
+                p!("~const ");
+            }
+        }
         if let ty::ImplPolarity::Negative = self.0.polarity {
             p!("!")
         }
-
         p!(print(self.0.trait_ref.print_only_trait_path()));
     }
 
@@ -2933,7 +2923,6 @@ define_print_and_forward_display! {
                 p!("~const ");
             }
         }
-        // FIXME(effects) print `~const` here
         if let ty::ImplPolarity::Negative = self.polarity {
             p!("!");
         }

compiler/rustc_middle/src/ty/util.rs

@@ -782,7 +782,7 @@ impl<'tcx> TyCtxt<'tcx> {
             || self.extern_crate(key.as_def_id()).is_some_and(|e| e.is_direct())
     }
 
-    pub fn expected_const_effect_param_for_body(self, def_id: LocalDefId) -> ty::Const<'tcx> {
+    pub fn expected_host_effect_param_for_body(self, def_id: LocalDefId) -> ty::Const<'tcx> {
         // FIXME(effects): This is suspicious and should probably not be done,
         // especially now that we enforce host effects and then properly handle
         // effect vars during fallback.
@@ -817,7 +817,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     /// Constructs generic args for an item, optionally appending a const effect param type
-    pub fn with_opt_const_effect_param(
+    pub fn with_opt_host_effect_param(
         self,
         caller_def_id: LocalDefId,
         callee_def_id: DefId,
@@ -826,9 +826,10 @@ impl<'tcx> TyCtxt<'tcx> {
         let generics = self.generics_of(callee_def_id);
         assert_eq!(generics.parent, None);
 
-        let opt_const_param = generics.host_effect_index.is_some().then(|| {
-            ty::GenericArg::from(self.expected_const_effect_param_for_body(caller_def_id))
-        });
+        let opt_const_param = generics
+            .host_effect_index
+            .is_some()
+            .then(|| ty::GenericArg::from(self.expected_host_effect_param_for_body(caller_def_id)));
 
         self.mk_args_from_iter(args.into_iter().map(|arg| arg.into()).chain(opt_const_param))
     }

compiler/rustc_mir_build/src/build/matches/test.rs

@@ -500,7 +500,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             self.tcx,
             eq_def_id,
             sym::eq,
-            self.tcx.with_opt_const_effect_param(self.def_id, eq_def_id, [ty, ty]),
+            self.tcx.with_opt_host_effect_param(self.def_id, eq_def_id, [ty, ty]),
         );
 
         let bool_ty = self.tcx.types.bool;

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

@@ -272,7 +272,7 @@ impl<'tcx> ConstToPat<'tcx> {
             ty::TraitRef::new(
                 tcx,
                 partial_eq_trait_id,
-                tcx.with_opt_const_effect_param(
+                tcx.with_opt_host_effect_param(
                     tcx.hir().enclosing_body_owner(self.id),
                     partial_eq_trait_id,
                     [ty, ty],

compiler/rustc_symbol_mangling/src/legacy.rs

@@ -342,6 +342,7 @@ impl<'tcx> Printer<'tcx> for SymbolPrinter<'tcx> {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
+        _params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError> {
         print_prefix(self)?;
 

compiler/rustc_symbol_mangling/src/v0.rs

@@ -298,6 +298,7 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
                     )
                 },
                 args,
+                &self.tcx.generics_of(impl_def_id).params,
             )?;
         } else {
             self.push_disambiguator(key.disambiguated_data.disambiguator as u64);
@@ -800,6 +801,7 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
+        _params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError> {
         // Don't print any regions if they're all erased.
         let print_regions = args.iter().any(|arg| match arg.unpack() {

tests/ui/rfcs/rfc-2632-const-trait-impl/call-const-trait-method-fail.stderr

@@ -2,7 +2,7 @@ error[E0277]: the trait bound `u32: ~const Plus` is not satisfied
   --> $DIR/call-const-trait-method-fail.rs:25:5
    |
 LL |     a.plus(b)
-   |     ^ the trait `Plus` is not implemented for `u32`
+   |     ^ the trait `~const Plus` is not implemented for `u32`
    |
    = help: the trait `Plus` is implemented for `u32`
 

tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.stderr

@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `S: ~const Foo<false>` is not satisfied
+error[E0277]: the trait bound `S: ~const Foo` is not satisfied
   --> $DIR/call-generic-method-nonconst.rs:23:34
    |
 LL | pub const EQ: bool = equals_self(&S);
-   |                      ----------- ^^ the trait `Foo<false>` is not implemented for `S`
+   |                      ----------- ^^ the trait `~const Foo` is not implemented for `S`
    |                      |
    |                      required by a bound introduced by this call
    |

tests/ui/rfcs/rfc-2632-const-trait-impl/const-default-method-bodies.stderr

@@ -2,7 +2,7 @@ error[E0277]: the trait bound `NonConstImpl: ~const ConstDefaultFn` is not satis
   --> $DIR/const-default-method-bodies.rs:24:18
    |
 LL |     NonConstImpl.a();
-   |                  ^ the trait `ConstDefaultFn` is not implemented for `NonConstImpl`
+   |                  ^ the trait `~const ConstDefaultFn` is not implemented for `NonConstImpl`
    |
    = help: the trait `ConstDefaultFn` is implemented for `NonConstImpl`
 

tests/ui/rfcs/rfc-2632-const-trait-impl/cross-crate.gatednc.stderr

@@ -2,7 +2,7 @@ error[E0277]: the trait bound `cross_crate::NonConst: ~const cross_crate::MyTrai
   --> $DIR/cross-crate.rs:17:14
    |
 LL |     NonConst.func();
-   |              ^^^^ the trait `cross_crate::MyTrait` is not implemented for `cross_crate::NonConst`
+   |              ^^^^ the trait `~const cross_crate::MyTrait` is not implemented for `cross_crate::NonConst`
    |
    = help: the trait `cross_crate::MyTrait` is implemented for `cross_crate::NonConst`