From 259a368e9eae8e9952d18e211d2fe0a7e5fae714 Mon Sep 17 00:00:00 2001 From: lcnr Date: Sun, 18 Apr 2021 13:57:22 +0200 Subject: [PATCH 1/4] fix name resolution for param defaults --- compiler/rustc_resolve/src/diagnostics.rs | 11 --- compiler/rustc_resolve/src/late.rs | 69 +++++++++++-------- compiler/rustc_resolve/src/lib.rs | 56 ++------------- .../defaults/complex-generic-default-expr.rs | 9 +++ .../complex-generic-default-expr.stderr | 16 +++++ .../defaults/default-on-impl.rs | 9 +++ .../defaults/default-on-impl.stderr | 8 +++ .../defaults/pretty-printing-ast.rs | 3 +- .../defaults/pretty-printing-ast.stdout | 3 +- .../defaults/type-default-const-param-name.rs | 17 +++++ ...ms-in-ct-in-ty-param-lazy-norm.full.stderr | 25 ++++--- ...ams-in-ct-in-ty-param-lazy-norm.min.stderr | 5 +- .../params-in-ct-in-ty-param-lazy-norm.rs | 4 +- .../generics/generic-non-trailing-defaults.rs | 1 + .../generic-non-trailing-defaults.stderr | 9 ++- 15 files changed, 141 insertions(+), 104 deletions(-) create mode 100644 src/test/ui/const-generics/defaults/complex-generic-default-expr.rs create mode 100644 src/test/ui/const-generics/defaults/complex-generic-default-expr.stderr create mode 100644 src/test/ui/const-generics/defaults/default-on-impl.rs create mode 100644 src/test/ui/const-generics/defaults/default-on-impl.stderr create mode 100644 src/test/ui/const-generics/defaults/type-default-const-param-name.rs diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs index 87e28f7fcc5..c5f12c0c691 100644 --- a/compiler/rustc_resolve/src/diagnostics.rs +++ b/compiler/rustc_resolve/src/diagnostics.rs @@ -472,17 +472,6 @@ impl<'a> Resolver<'a> { ); err } - ResolutionError::ParamInAnonConstInTyDefault(name) => { - let mut err = self.session.struct_span_err( - span, - "constant values inside of type parameter defaults must not depend on generic parameters", - ); - err.span_label( - span, - format!("the anonymous constant must not depend on the parameter `{}`", name), - ); - err - } ResolutionError::ParamInNonTrivialAnonConst { name, is_type } => { let mut err = self.session.struct_span_err( span, diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs index 9321f11f659..92f21191de4 100644 --- a/compiler/rustc_resolve/src/late.rs +++ b/compiler/rustc_resolve/src/late.rs @@ -555,18 +555,23 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> { // provide previous type parameters as they're built. We // put all the parameters on the ban list and then remove // them one by one as they are processed and become available. - let mut default_ban_rib = Rib::new(ForwardGenericParamBanRibKind); - let mut found_default = false; - default_ban_rib.bindings.extend(generics.params.iter().filter_map( - |param| match param.kind { - GenericParamKind::Type { default: Some(_), .. } - | GenericParamKind::Const { default: Some(_), .. } => { - found_default = true; - Some((Ident::with_dummy_span(param.ident.name), Res::Err)) + let mut forward_ty_ban_rib = Rib::new(ForwardGenericParamBanRibKind); + let mut forward_const_ban_rib = Rib::new(ForwardGenericParamBanRibKind); + for param in generics.params.iter() { + match param.kind { + GenericParamKind::Type { .. } => { + forward_ty_ban_rib + .bindings + .insert(Ident::with_dummy_span(param.ident.name), Res::Err); } - _ => None, - }, - )); + GenericParamKind::Const { .. } => { + forward_const_ban_rib + .bindings + .insert(Ident::with_dummy_span(param.ident.name), Res::Err); + } + GenericParamKind::Lifetime => {} + } + } // rust-lang/rust#61631: The type `Self` is essentially // another type parameter. For ADTs, we consider it @@ -579,7 +584,7 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> { // such as in the case of `trait Add`.) if self.diagnostic_metadata.current_self_item.is_some() { // (`Some` if + only if we are in ADT's generics.) - default_ban_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), Res::Err); + forward_ty_ban_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), Res::Err); } for param in &generics.params { @@ -591,32 +596,38 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> { } if let Some(ref ty) = default { - self.ribs[TypeNS].push(default_ban_rib); - self.with_rib(ValueNS, ForwardGenericParamBanRibKind, |this| { - // HACK: We use an empty `ForwardGenericParamBanRibKind` here which - // is only used to forbid the use of const parameters inside of - // type defaults. - // - // While the rib name doesn't really fit here, it does allow us to use the same - // code for both const and type parameters. - this.visit_ty(ty); - }); - default_ban_rib = self.ribs[TypeNS].pop().unwrap(); + self.ribs[TypeNS].push(forward_ty_ban_rib); + self.ribs[ValueNS].push(forward_const_ban_rib); + self.visit_ty(ty); + forward_const_ban_rib = self.ribs[ValueNS].pop().unwrap(); + forward_ty_ban_rib = self.ribs[TypeNS].pop().unwrap(); } // Allow all following defaults to refer to this type parameter. - default_ban_rib.bindings.remove(&Ident::with_dummy_span(param.ident.name)); + forward_ty_ban_rib.bindings.remove(&Ident::with_dummy_span(param.ident.name)); } - GenericParamKind::Const { ref ty, kw_span: _, default: _ } => { - // FIXME(const_generics_defaults): handle `default` value here - for bound in ¶m.bounds { - self.visit_param_bound(bound); - } + GenericParamKind::Const { ref ty, kw_span: _, ref default } => { + // Const parameters can't have param bounds. + assert!(param.bounds.is_empty()); + self.ribs[TypeNS].push(Rib::new(ConstParamTyRibKind)); self.ribs[ValueNS].push(Rib::new(ConstParamTyRibKind)); self.visit_ty(ty); self.ribs[TypeNS].pop().unwrap(); self.ribs[ValueNS].pop().unwrap(); + + if let Some(ref expr) = default { + self.ribs[TypeNS].push(forward_ty_ban_rib); + self.ribs[ValueNS].push(forward_const_ban_rib); + self.visit_anon_const(expr); + forward_const_ban_rib = self.ribs[ValueNS].pop().unwrap(); + forward_ty_ban_rib = self.ribs[TypeNS].pop().unwrap(); + } + + // Allow all following defaults to refer to this const parameter. + forward_const_ban_rib + .bindings + .remove(&Ident::with_dummy_span(param.ident.name)); } } } diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs index 129954381c9..1d1969f7e78 100644 --- a/compiler/rustc_resolve/src/lib.rs +++ b/compiler/rustc_resolve/src/lib.rs @@ -239,8 +239,6 @@ enum ResolutionError<'a> { ForwardDeclaredTyParam, // FIXME(const_generics_defaults) /// ERROR E0770: the type of const parameters must not depend on other generic parameters. ParamInTyOfConstParam(Symbol), - /// constant values inside of type parameter defaults must not depend on generic parameters. - ParamInAnonConstInTyDefault(Symbol), /// generic parameters must not be used inside const evaluations. /// /// This error is only emitted when using `min_const_generics`. @@ -2672,26 +2670,18 @@ impl<'a> Resolver<'a> { } } Res::Def(DefKind::TyParam, _) | Res::SelfTy(..) => { - let mut in_ty_param_default = false; for rib in ribs { - let has_generic_params = match rib.kind { + let has_generic_params: HasGenericParams = match rib.kind { NormalRibKind | ClosureOrAsyncRibKind | AssocItemRibKind | ModuleRibKind(..) - | MacroDefinition(..) => { + | MacroDefinition(..) + | ForwardGenericParamBanRibKind => { // Nothing to do. Continue. continue; } - // We only forbid constant items if we are inside of type defaults, - // for example `struct Foo()]>` - ForwardGenericParamBanRibKind => { - // FIXME(const_generic_defaults): we may need to distinguish between - // being in type parameter defaults and const parameter defaults - in_ty_param_default = true; - continue; - } ConstantItemRibKind(trivial, _) => { let features = self.session.features_untracked(); // HACK(min_const_generics): We currently only allow `N` or `{ N }`. @@ -2720,19 +2710,7 @@ impl<'a> Resolver<'a> { } } - if in_ty_param_default { - if record_used { - self.report_error( - span, - ResolutionError::ParamInAnonConstInTyDefault( - rib_ident.name, - ), - ); - } - return Res::Err; - } else { - continue; - } + continue; } // This was an attempt to use a type parameter outside its scope. @@ -2770,23 +2748,15 @@ impl<'a> Resolver<'a> { ribs.next(); } - let mut in_ty_param_default = false; for rib in ribs { let has_generic_params = match rib.kind { NormalRibKind | ClosureOrAsyncRibKind | AssocItemRibKind | ModuleRibKind(..) - | MacroDefinition(..) => continue, + | MacroDefinition(..) + | ForwardGenericParamBanRibKind => continue, - // We only forbid constant items if we are inside of type defaults, - // for example `struct Foo()]>` - ForwardGenericParamBanRibKind => { - // FIXME(const_generic_defaults): we may need to distinguish between - // being in type parameter defaults and const parameter defaults - in_ty_param_default = true; - continue; - } ConstantItemRibKind(trivial, _) => { let features = self.session.features_untracked(); // HACK(min_const_generics): We currently only allow `N` or `{ N }`. @@ -2808,19 +2778,7 @@ impl<'a> Resolver<'a> { return Res::Err; } - if in_ty_param_default { - if record_used { - self.report_error( - span, - ResolutionError::ParamInAnonConstInTyDefault( - rib_ident.name, - ), - ); - } - return Res::Err; - } else { - continue; - } + continue; } ItemRibKind(has_generic_params) => has_generic_params, diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs new file mode 100644 index 00000000000..ba00e4b15ca --- /dev/null +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs @@ -0,0 +1,9 @@ +#![feature(const_generics, const_generics_defaults)] +#![allow(incomplete_features)] + +struct Foo; + +struct Bar() }>(T); +//~^ ERROR the size for values of type `T` cannot be known at compilation time + +fn main() {} diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.stderr b/src/test/ui/const-generics/defaults/complex-generic-default-expr.stderr new file mode 100644 index 00000000000..06865fdd8fd --- /dev/null +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.stderr @@ -0,0 +1,16 @@ +error[E0277]: the size for values of type `T` cannot be known at compilation time + --> $DIR/complex-generic-default-expr.rs:6:62 + | +LL | struct Bar() }>(T); + | - ^ doesn't have a size known at compile-time + | | + | this type parameter needs to be `std::marker::Sized` + | + ::: $SRC_DIR/core/src/mem/mod.rs:LL:COL + | +LL | pub const fn size_of() -> usize { + | - required by this bound in `std::mem::size_of` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. diff --git a/src/test/ui/const-generics/defaults/default-on-impl.rs b/src/test/ui/const-generics/defaults/default-on-impl.rs new file mode 100644 index 00000000000..2555450a9e7 --- /dev/null +++ b/src/test/ui/const-generics/defaults/default-on-impl.rs @@ -0,0 +1,9 @@ +#![feature(const_generics, const_generics_defaults)] +#![allow(incomplete_features)] + +struct Foo; + +impl Foo {} +//~^ ERROR defaults for const parameters are only allowed + +fn main() {} diff --git a/src/test/ui/const-generics/defaults/default-on-impl.stderr b/src/test/ui/const-generics/defaults/default-on-impl.stderr new file mode 100644 index 00000000000..b30b18a7b3c --- /dev/null +++ b/src/test/ui/const-generics/defaults/default-on-impl.stderr @@ -0,0 +1,8 @@ +error: defaults for const parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions + --> $DIR/default-on-impl.rs:6:12 + | +LL | impl Foo {} + | ^ + +error: aborting due to previous error + diff --git a/src/test/ui/const-generics/defaults/pretty-printing-ast.rs b/src/test/ui/const-generics/defaults/pretty-printing-ast.rs index a25d4baca1a..12a92a10476 100644 --- a/src/test/ui/const-generics/defaults/pretty-printing-ast.rs +++ b/src/test/ui/const-generics/defaults/pretty-printing-ast.rs @@ -10,4 +10,5 @@ trait Foo {} fn foo() {} -struct Range; +struct Range; + diff --git a/src/test/ui/const-generics/defaults/pretty-printing-ast.stdout b/src/test/ui/const-generics/defaults/pretty-printing-ast.stdout index f7a1d2ca4b2..c514bbe72e1 100644 --- a/src/test/ui/const-generics/defaults/pretty-printing-ast.stdout +++ b/src/test/ui/const-generics/defaults/pretty-printing-ast.stdout @@ -17,4 +17,5 @@ trait Foo { } fn foo() { } struct Range; + FROM>; + diff --git a/src/test/ui/const-generics/defaults/type-default-const-param-name.rs b/src/test/ui/const-generics/defaults/type-default-const-param-name.rs new file mode 100644 index 00000000000..c0c83cda285 --- /dev/null +++ b/src/test/ui/const-generics/defaults/type-default-const-param-name.rs @@ -0,0 +1,17 @@ +// check-pass +#![feature(const_generics, const_generics_defaults)] +#![allow(incomplete_features)] + +struct N; + +struct Foo(T); + +impl Foo { + fn new() -> Self { + Foo(N) + } +} + +fn main() { + let Foo::<1, N>(N) = Foo::new(); +} diff --git a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr index c2b7b206653..d8bfab6aa52 100644 --- a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr +++ b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr @@ -6,17 +6,26 @@ LL | struct Bar(T); | = note: using type defaults and const parameters in the same parameter list is currently not permitted -error: constant values inside of type parameter defaults must not depend on generic parameters - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:6:44 - | -LL | struct Foo()]>(T, U); - | ^ the anonymous constant must not depend on the parameter `T` - -error: constant values inside of type parameter defaults must not depend on generic parameters +error[E0128]: generic parameters with a default cannot use forward declared identifiers --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:21 | LL | struct Bar(T); - | ^ the anonymous constant must not depend on the parameter `N` + | ^ defaulted generic parameters cannot be forward declared + +error[E0277]: the size for values of type `T` cannot be known at compilation time + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:6:44 + | +LL | struct Foo()]>(T, U); + | - ^ doesn't have a size known at compile-time + | | + | this type parameter needs to be `std::marker::Sized` + | + ::: $SRC_DIR/core/src/mem/mod.rs:LL:COL + | +LL | pub const fn size_of() -> usize { + | - required by this bound in `std::mem::size_of` error: aborting due to 3 previous errors +Some errors have detailed explanations: E0128, E0277. +For more information about an error, try `rustc --explain E0128`. diff --git a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr index 4a462c328bf..44393a30266 100644 --- a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr +++ b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr @@ -15,11 +15,12 @@ LL | struct Foo()]>(T, U); = note: type parameters may not be used in const expressions = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions -error: constant values inside of type parameter defaults must not depend on generic parameters +error[E0128]: generic parameters with a default cannot use forward declared identifiers --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:21 | LL | struct Bar(T); - | ^ the anonymous constant must not depend on the parameter `N` + | ^ defaulted generic parameters cannot be forward declared error: aborting due to 3 previous errors +For more information about this error, try `rustc --explain E0128`. diff --git a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs index c7be8bdaf9c..8a84afd065c 100644 --- a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs +++ b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs @@ -4,12 +4,12 @@ #![cfg_attr(full, allow(incomplete_features))] struct Foo()]>(T, U); -//[full]~^ ERROR constant values inside of type parameter defaults +//[full]~^ ERROR the size for values of type `T` cannot be known at compilation time //[min]~^^ ERROR generic parameters may not be used in const operations // FIXME(const_generics_defaults): We still don't know how to deal with type defaults. struct Bar(T); -//~^ ERROR constant values inside of type parameter defaults +//~^ ERROR generic parameters with a default cannot use forward declared identifiers //~| ERROR generic parameters with a default fn main() {} diff --git a/src/test/ui/generics/generic-non-trailing-defaults.rs b/src/test/ui/generics/generic-non-trailing-defaults.rs index cb2bb2832b7..16ea71d48c8 100644 --- a/src/test/ui/generics/generic-non-trailing-defaults.rs +++ b/src/test/ui/generics/generic-non-trailing-defaults.rs @@ -5,5 +5,6 @@ struct Vec(A, T); struct Foo, C>(A, B, C); //~^ ERROR generic parameters with a default must be trailing +//~| ERROR generic parameters with a default cannot use fn main() {} diff --git a/src/test/ui/generics/generic-non-trailing-defaults.stderr b/src/test/ui/generics/generic-non-trailing-defaults.stderr index 6d768617503..713ba091b86 100644 --- a/src/test/ui/generics/generic-non-trailing-defaults.stderr +++ b/src/test/ui/generics/generic-non-trailing-defaults.stderr @@ -10,5 +10,12 @@ error: generic parameters with a default must be trailing LL | struct Foo, C>(A, B, C); | ^ -error: aborting due to 2 previous errors +error[E0128]: generic parameters with a default cannot use forward declared identifiers + --> $DIR/generic-non-trailing-defaults.rs:6:23 + | +LL | struct Foo, C>(A, B, C); + | ^ defaulted generic parameters cannot be forward declared +error: aborting due to 3 previous errors + +For more information about this error, try `rustc --explain E0128`. From 7cb1dcd48802378929032ad9363c296891443d76 Mon Sep 17 00:00:00 2001 From: lcnr Date: Sun, 18 Apr 2021 14:31:00 +0200 Subject: [PATCH 2/4] loosen ordering restricts for `const_generics_defaults` --- .../rustc_ast_passes/src/ast_validation.rs | 2 +- compiler/rustc_feature/src/active.rs | 4 ++ compiler/rustc_hir/src/hir.rs | 4 +- compiler/rustc_middle/src/ty/generics.rs | 2 +- compiler/rustc_typeck/src/astconv/generics.rs | 6 ++- .../defaults/auxiliary/const_defaulty.rs | 2 +- ... complex-generic-default-expr.full.stderr} | 2 +- .../complex-generic-default-expr.min.stderr | 20 +++++++ .../defaults/complex-generic-default-expr.rs | 8 ++- .../const-generics/defaults/const-default.rs | 4 +- ...mpl.stderr => default-on-impl.full.stderr} | 2 +- .../defaults/default-on-impl.min.stderr | 8 +++ .../defaults/default-on-impl.rs | 4 +- .../ui/const-generics/defaults/external.rs | 2 + .../defaults/intermixed-lifetime.full.stderr | 2 +- .../defaults/intermixed-lifetime.min.stderr | 22 ++------ .../defaults/intermixed-lifetime.rs | 10 ++-- .../{mismatch.stderr => mismatch.full.stderr} | 10 ++-- .../defaults/mismatch.min.stderr | 52 +++++++++++++++++++ .../ui/const-generics/defaults/mismatch.rs | 3 +- .../defaults/pretty-printing-ast.stdout | 1 - .../defaults/repr-c-issue-82792.rs | 2 +- .../defaults/simple-defaults.min.stderr | 8 --- .../defaults/simple-defaults.rs | 10 ++-- .../defaults/type-default-const-param-name.rs | 4 +- .../defaults/wrong-order.full.stderr | 15 +----- .../defaults/wrong-order.min.stderr | 4 +- .../ui/const-generics/defaults/wrong-order.rs | 4 +- ...ms-in-ct-in-ty-param-lazy-norm.full.stderr | 4 +- ...ams-in-ct-in-ty-param-lazy-norm.min.stderr | 4 +- .../params-in-ct-in-ty-param-lazy-norm.rs | 1 - 31 files changed, 145 insertions(+), 81 deletions(-) rename src/test/ui/const-generics/defaults/{complex-generic-default-expr.stderr => complex-generic-default-expr.full.stderr} (93%) create mode 100644 src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr rename src/test/ui/const-generics/defaults/{default-on-impl.stderr => default-on-impl.full.stderr} (85%) create mode 100644 src/test/ui/const-generics/defaults/default-on-impl.min.stderr rename src/test/ui/const-generics/defaults/{mismatch.stderr => mismatch.full.stderr} (90%) create mode 100644 src/test/ui/const-generics/defaults/mismatch.min.stderr delete mode 100644 src/test/ui/const-generics/defaults/simple-defaults.min.stderr diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs index bb09f701531..e79392adf74 100644 --- a/compiler/rustc_ast_passes/src/ast_validation.rs +++ b/compiler/rustc_ast_passes/src/ast_validation.rs @@ -754,7 +754,7 @@ fn validate_generic_param_order( GenericParamKind::Type { default: _ } => (ParamKindOrd::Type, ident), GenericParamKind::Const { ref ty, kw_span: _, default: _ } => { let ty = pprust::ty_to_string(ty); - let unordered = sess.features_untracked().const_generics; + let unordered = sess.features_untracked().unordered_const_ty_params(); (ParamKindOrd::Const { unordered }, Some(format!("const {}: {}", param.ident, ty))) } }; diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs index 6fd1af60fe2..80f237148c3 100644 --- a/compiler/rustc_feature/src/active.rs +++ b/compiler/rustc_feature/src/active.rs @@ -63,6 +63,10 @@ macro_rules! declare_features { _ => panic!("`{}` was not listed in `declare_features`", feature), } } + + pub fn unordered_const_ty_params(&self) -> bool { + self.const_generics || self.const_generics_defaults + } } }; } diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs index 1051fb8cea2..a70be14546b 100644 --- a/compiler/rustc_hir/src/hir.rs +++ b/compiler/rustc_hir/src/hir.rs @@ -296,7 +296,9 @@ impl GenericArg<'_> { match self { GenericArg::Lifetime(_) => ast::ParamKindOrd::Lifetime, GenericArg::Type(_) => ast::ParamKindOrd::Type, - GenericArg::Const(_) => ast::ParamKindOrd::Const { unordered: feats.const_generics }, + GenericArg::Const(_) => { + ast::ParamKindOrd::Const { unordered: feats.unordered_const_ty_params() } + } } } } diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs index d30a8693959..c8fdbc30d15 100644 --- a/compiler/rustc_middle/src/ty/generics.rs +++ b/compiler/rustc_middle/src/ty/generics.rs @@ -36,7 +36,7 @@ impl GenericParamDefKind { GenericParamDefKind::Lifetime => ast::ParamKindOrd::Lifetime, GenericParamDefKind::Type { .. } => ast::ParamKindOrd::Type, GenericParamDefKind::Const { .. } => { - ast::ParamKindOrd::Const { unordered: tcx.features().const_generics } + ast::ParamKindOrd::Const { unordered: tcx.features().unordered_const_ty_params() } } } } diff --git a/compiler/rustc_typeck/src/astconv/generics.rs b/compiler/rustc_typeck/src/astconv/generics.rs index 7a297f2c65f..2bbb38c294d 100644 --- a/compiler/rustc_typeck/src/astconv/generics.rs +++ b/compiler/rustc_typeck/src/astconv/generics.rs @@ -286,7 +286,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { ParamKindOrd::Const { unordered: tcx .features() - .const_generics, + .unordered_const_ty_params(), } } }, @@ -309,7 +309,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { GenericArg::Lifetime(_) => ParamKindOrd::Lifetime, GenericArg::Type(_) => ParamKindOrd::Type, GenericArg::Const(_) => ParamKindOrd::Const { - unordered: tcx.features().const_generics, + unordered: tcx + .features() + .unordered_const_ty_params(), }, }), Some(&format!( diff --git a/src/test/ui/const-generics/defaults/auxiliary/const_defaulty.rs b/src/test/ui/const-generics/defaults/auxiliary/const_defaulty.rs index 769b6e952dc..6514409698e 100644 --- a/src/test/ui/const-generics/defaults/auxiliary/const_defaulty.rs +++ b/src/test/ui/const-generics/defaults/auxiliary/const_defaulty.rs @@ -1,4 +1,4 @@ -#![feature(const_generics)] +#![cfg_attr(full, feature(const_generics))] #![feature(const_generics_defaults)] #![allow(incomplete_features)] diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.stderr b/src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr similarity index 93% rename from src/test/ui/const-generics/defaults/complex-generic-default-expr.stderr rename to src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr index 06865fdd8fd..c1444abbd3f 100644 --- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.stderr +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr @@ -1,5 +1,5 @@ error[E0277]: the size for values of type `T` cannot be known at compilation time - --> $DIR/complex-generic-default-expr.rs:6:62 + --> $DIR/complex-generic-default-expr.rs:9:62 | LL | struct Bar() }>(T); | - ^ doesn't have a size known at compile-time diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr b/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr new file mode 100644 index 00000000000..d50a0a61d49 --- /dev/null +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr @@ -0,0 +1,20 @@ +error: generic parameters may not be used in const operations + --> $DIR/complex-generic-default-expr.rs:6:47 + | +LL | struct Foo; + | ^ cannot perform const operation using `N` + | + = help: const parameters may only be used as standalone arguments, i.e. `N` + = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions + +error: generic parameters may not be used in const operations + --> $DIR/complex-generic-default-expr.rs:9:62 + | +LL | struct Bar() }>(T); + | ^ cannot perform const operation using `T` + | + = note: type parameters may not be used in const expressions + = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions + +error: aborting due to 2 previous errors + diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs index ba00e4b15ca..1c25fda8d30 100644 --- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs @@ -1,9 +1,13 @@ -#![feature(const_generics, const_generics_defaults)] +// revisions: full min +#![cfg_attr(full, feature(const_generics))] +#![feature(const_generics_defaults)] #![allow(incomplete_features)] struct Foo; +//[min]~^ ERROR generic parameters may not be used in const operations struct Bar() }>(T); -//~^ ERROR the size for values of type `T` cannot be known at compilation time +//[min]~^ ERROR generic parameters may not be used in const operations +//[full]~^^ ERROR the size for values of type `T` cannot be known at compilation time fn main() {} diff --git a/src/test/ui/const-generics/defaults/const-default.rs b/src/test/ui/const-generics/defaults/const-default.rs index 150c70770ae..4fa21b8b1fb 100644 --- a/src/test/ui/const-generics/defaults/const-default.rs +++ b/src/test/ui/const-generics/defaults/const-default.rs @@ -1,6 +1,6 @@ // run-pass - -#![feature(const_generics)] +// revisions: full min +#![cfg_attr(full, feature(const_generics))] #![feature(const_generics_defaults)] #![allow(incomplete_features)] diff --git a/src/test/ui/const-generics/defaults/default-on-impl.stderr b/src/test/ui/const-generics/defaults/default-on-impl.full.stderr similarity index 85% rename from src/test/ui/const-generics/defaults/default-on-impl.stderr rename to src/test/ui/const-generics/defaults/default-on-impl.full.stderr index b30b18a7b3c..c417a26842e 100644 --- a/src/test/ui/const-generics/defaults/default-on-impl.stderr +++ b/src/test/ui/const-generics/defaults/default-on-impl.full.stderr @@ -1,5 +1,5 @@ error: defaults for const parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions - --> $DIR/default-on-impl.rs:6:12 + --> $DIR/default-on-impl.rs:8:12 | LL | impl Foo {} | ^ diff --git a/src/test/ui/const-generics/defaults/default-on-impl.min.stderr b/src/test/ui/const-generics/defaults/default-on-impl.min.stderr new file mode 100644 index 00000000000..c417a26842e --- /dev/null +++ b/src/test/ui/const-generics/defaults/default-on-impl.min.stderr @@ -0,0 +1,8 @@ +error: defaults for const parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions + --> $DIR/default-on-impl.rs:8:12 + | +LL | impl Foo {} + | ^ + +error: aborting due to previous error + diff --git a/src/test/ui/const-generics/defaults/default-on-impl.rs b/src/test/ui/const-generics/defaults/default-on-impl.rs index 2555450a9e7..735549defea 100644 --- a/src/test/ui/const-generics/defaults/default-on-impl.rs +++ b/src/test/ui/const-generics/defaults/default-on-impl.rs @@ -1,4 +1,6 @@ -#![feature(const_generics, const_generics_defaults)] +// revisions: full min +#![cfg_attr(full, feature(const_generics))] +#![feature(const_generics_defaults)] #![allow(incomplete_features)] struct Foo; diff --git a/src/test/ui/const-generics/defaults/external.rs b/src/test/ui/const-generics/defaults/external.rs index b39e69ab10b..32acf567cf2 100644 --- a/src/test/ui/const-generics/defaults/external.rs +++ b/src/test/ui/const-generics/defaults/external.rs @@ -1,5 +1,7 @@ // aux-build:const_defaulty.rs // check-pass +// revisions: full min +#![cfg_attr(full, feature(const_generics))] #![feature(const_generics_defaults)] #![allow(incomplete_features)] diff --git a/src/test/ui/const-generics/defaults/intermixed-lifetime.full.stderr b/src/test/ui/const-generics/defaults/intermixed-lifetime.full.stderr index c4a666a829d..29d835e36c6 100644 --- a/src/test/ui/const-generics/defaults/intermixed-lifetime.full.stderr +++ b/src/test/ui/const-generics/defaults/intermixed-lifetime.full.stderr @@ -1,5 +1,5 @@ error: lifetime parameters must be declared prior to const parameters - --> $DIR/intermixed-lifetime.rs:6:28 + --> $DIR/intermixed-lifetime.rs:7:28 | LL | struct Foo(&'a (), T); | -----------------^^---------- help: reorder the parameters: lifetimes, then consts and types: `<'a, const N: usize, T = u32>` diff --git a/src/test/ui/const-generics/defaults/intermixed-lifetime.min.stderr b/src/test/ui/const-generics/defaults/intermixed-lifetime.min.stderr index 69a490978d1..985e7b655ec 100644 --- a/src/test/ui/const-generics/defaults/intermixed-lifetime.min.stderr +++ b/src/test/ui/const-generics/defaults/intermixed-lifetime.min.stderr @@ -1,26 +1,14 @@ error: lifetime parameters must be declared prior to const parameters - --> $DIR/intermixed-lifetime.rs:6:28 + --> $DIR/intermixed-lifetime.rs:7:28 | LL | struct Foo(&'a (), T); - | -----------------^^---------- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>` + | -----------------^^---------- help: reorder the parameters: lifetimes, then types, then consts: `<'a, const N: usize, T = u32>` -error: type parameters must be declared prior to const parameters - --> $DIR/intermixed-lifetime.rs:6:32 - | -LL | struct Foo(&'a (), T); - | ---------------------^------- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>` - -error: lifetime parameters must be declared prior to const parameters +error: lifetime parameters must be declared prior to type parameters --> $DIR/intermixed-lifetime.rs:10:37 | LL | struct Bar(&'a (), T); - | --------------------------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>` + | --------------------------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, const N: usize, T = u32>` -error: type parameters must be declared prior to const parameters - --> $DIR/intermixed-lifetime.rs:10:28 - | -LL | struct Bar(&'a (), T); - | -----------------^----------- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>` - -error: aborting due to 4 previous errors +error: aborting due to 2 previous errors diff --git a/src/test/ui/const-generics/defaults/intermixed-lifetime.rs b/src/test/ui/const-generics/defaults/intermixed-lifetime.rs index 9e83bf92a59..307e3aaf1fb 100644 --- a/src/test/ui/const-generics/defaults/intermixed-lifetime.rs +++ b/src/test/ui/const-generics/defaults/intermixed-lifetime.rs @@ -1,15 +1,13 @@ -// revisions: full min // Checks that lifetimes cannot be interspersed between consts and types. +// revisions: full min #![cfg_attr(full, feature(const_generics))] -#![cfg_attr(full, allow(incomplete_features))] +#![feature(const_generics_defaults)] +#![allow(incomplete_features)] struct Foo(&'a (), T); //~^ Error lifetime parameters must be declared prior to const parameters -//[min]~^^ Error type parameters must be declared prior to const parameters struct Bar(&'a (), T); -//[full]~^ Error lifetime parameters must be declared prior to type parameters -//[min]~^^ Error type parameters must be declared prior to const parameters -//[min]~| Error lifetime parameters must be declared prior to const parameters +//~^ Error lifetime parameters must be declared prior to type parameters fn main() {} diff --git a/src/test/ui/const-generics/defaults/mismatch.stderr b/src/test/ui/const-generics/defaults/mismatch.full.stderr similarity index 90% rename from src/test/ui/const-generics/defaults/mismatch.stderr rename to src/test/ui/const-generics/defaults/mismatch.full.stderr index ff72c71c40f..be4f364d8ee 100644 --- a/src/test/ui/const-generics/defaults/mismatch.stderr +++ b/src/test/ui/const-generics/defaults/mismatch.full.stderr @@ -1,5 +1,5 @@ error[E0308]: mismatched types - --> $DIR/mismatch.rs:11:28 + --> $DIR/mismatch.rs:12:28 | LL | let e: Example::<13> = (); | ------------- ^^ expected struct `Example`, found `()` @@ -7,7 +7,7 @@ LL | let e: Example::<13> = (); | expected due to this error[E0308]: mismatched types - --> $DIR/mismatch.rs:13:34 + --> $DIR/mismatch.rs:14:34 | LL | let e: Example2:: = (); | ------------------- ^^ expected struct `Example2`, found `()` @@ -18,7 +18,7 @@ LL | let e: Example2:: = (); found unit type `()` error[E0308]: mismatched types - --> $DIR/mismatch.rs:15:34 + --> $DIR/mismatch.rs:16:34 | LL | let e: Example3::<13, u32> = (); | ------------------- ^^ expected struct `Example3`, found `()` @@ -29,7 +29,7 @@ LL | let e: Example3::<13, u32> = (); found unit type `()` error[E0308]: mismatched types - --> $DIR/mismatch.rs:17:28 + --> $DIR/mismatch.rs:18:28 | LL | let e: Example3::<7> = (); | ------------- ^^ expected struct `Example3`, found `()` @@ -40,7 +40,7 @@ LL | let e: Example3::<7> = (); found unit type `()` error[E0308]: mismatched types - --> $DIR/mismatch.rs:21:28 + --> $DIR/mismatch.rs:22:28 | LL | let e: Example4::<7> = (); | ------------- ^^ expected struct `Example4`, found `()` diff --git a/src/test/ui/const-generics/defaults/mismatch.min.stderr b/src/test/ui/const-generics/defaults/mismatch.min.stderr new file mode 100644 index 00000000000..be4f364d8ee --- /dev/null +++ b/src/test/ui/const-generics/defaults/mismatch.min.stderr @@ -0,0 +1,52 @@ +error[E0308]: mismatched types + --> $DIR/mismatch.rs:12:28 + | +LL | let e: Example::<13> = (); + | ------------- ^^ expected struct `Example`, found `()` + | | + | expected due to this + +error[E0308]: mismatched types + --> $DIR/mismatch.rs:14:34 + | +LL | let e: Example2:: = (); + | ------------------- ^^ expected struct `Example2`, found `()` + | | + | expected due to this + | + = note: expected struct `Example2` + found unit type `()` + +error[E0308]: mismatched types + --> $DIR/mismatch.rs:16:34 + | +LL | let e: Example3::<13, u32> = (); + | ------------------- ^^ expected struct `Example3`, found `()` + | | + | expected due to this + | + = note: expected struct `Example3` + found unit type `()` + +error[E0308]: mismatched types + --> $DIR/mismatch.rs:18:28 + | +LL | let e: Example3::<7> = (); + | ------------- ^^ expected struct `Example3`, found `()` + | | + | expected due to this + | + = note: expected struct `Example3<7_usize>` + found unit type `()` + +error[E0308]: mismatched types + --> $DIR/mismatch.rs:22:28 + | +LL | let e: Example4::<7> = (); + | ------------- ^^ expected struct `Example4`, found `()` + | | + | expected due to this + +error: aborting due to 5 previous errors + +For more information about this error, try `rustc --explain E0308`. diff --git a/src/test/ui/const-generics/defaults/mismatch.rs b/src/test/ui/const-generics/defaults/mismatch.rs index d85b756f538..68a640c0a08 100644 --- a/src/test/ui/const-generics/defaults/mismatch.rs +++ b/src/test/ui/const-generics/defaults/mismatch.rs @@ -1,4 +1,5 @@ -#![feature(const_generics)] +// revisions: full min +#![cfg_attr(full, feature(const_generics))] #![feature(const_generics_defaults)] #![allow(incomplete_features)] diff --git a/src/test/ui/const-generics/defaults/pretty-printing-ast.stdout b/src/test/ui/const-generics/defaults/pretty-printing-ast.stdout index c514bbe72e1..f549993c413 100644 --- a/src/test/ui/const-generics/defaults/pretty-printing-ast.stdout +++ b/src/test/ui/const-generics/defaults/pretty-printing-ast.stdout @@ -18,4 +18,3 @@ fn foo() { } struct Range; - diff --git a/src/test/ui/const-generics/defaults/repr-c-issue-82792.rs b/src/test/ui/const-generics/defaults/repr-c-issue-82792.rs index 18ecf467299..c64c2974c8f 100644 --- a/src/test/ui/const-generics/defaults/repr-c-issue-82792.rs +++ b/src/test/ui/const-generics/defaults/repr-c-issue-82792.rs @@ -6,7 +6,7 @@ #![allow(incomplete_features)] #[repr(C)] -pub struct Loaf { +pub struct Loaf { head: [T; N], slice: [T], } diff --git a/src/test/ui/const-generics/defaults/simple-defaults.min.stderr b/src/test/ui/const-generics/defaults/simple-defaults.min.stderr deleted file mode 100644 index 0746c64ac8c..00000000000 --- a/src/test/ui/const-generics/defaults/simple-defaults.min.stderr +++ /dev/null @@ -1,8 +0,0 @@ -error: type parameters must be declared prior to const parameters - --> $DIR/simple-defaults.rs:8:40 - | -LL | struct FixedOutput<'a, const N: usize, T=u32> { - | ---------------------^----- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>` - -error: aborting due to previous error - diff --git a/src/test/ui/const-generics/defaults/simple-defaults.rs b/src/test/ui/const-generics/defaults/simple-defaults.rs index cb66c7769bb..c003cb2c5a6 100644 --- a/src/test/ui/const-generics/defaults/simple-defaults.rs +++ b/src/test/ui/const-generics/defaults/simple-defaults.rs @@ -1,12 +1,12 @@ -// [full] run-pass -// revisions: min full -// Checks some basic test cases for defaults. +// run-pass +// Checks that type param defaults are allowed after const params. +// revisions: full min #![cfg_attr(full, feature(const_generics))] -#![cfg_attr(full, allow(incomplete_features))] +#![feature(const_generics_defaults)] +#![allow(incomplete_features)] #![allow(dead_code)] struct FixedOutput<'a, const N: usize, T=u32> { - //[min]~^ ERROR type parameters must be declared prior to const parameters out: &'a [T; N], } diff --git a/src/test/ui/const-generics/defaults/type-default-const-param-name.rs b/src/test/ui/const-generics/defaults/type-default-const-param-name.rs index c0c83cda285..e68075ee3c6 100644 --- a/src/test/ui/const-generics/defaults/type-default-const-param-name.rs +++ b/src/test/ui/const-generics/defaults/type-default-const-param-name.rs @@ -1,5 +1,7 @@ // check-pass -#![feature(const_generics, const_generics_defaults)] +// revisions: full min +#![cfg_attr(full, feature(const_generics))] +#![feature(const_generics_defaults)] #![allow(incomplete_features)] struct N; diff --git a/src/test/ui/const-generics/defaults/wrong-order.full.stderr b/src/test/ui/const-generics/defaults/wrong-order.full.stderr index accc73134d8..eb0bcb28215 100644 --- a/src/test/ui/const-generics/defaults/wrong-order.full.stderr +++ b/src/test/ui/const-generics/defaults/wrong-order.full.stderr @@ -1,19 +1,8 @@ error: generic parameters with a default must be trailing - --> $DIR/wrong-order.rs:4:10 + --> $DIR/wrong-order.rs:6:10 | LL | struct A { | ^ - | - = note: using type defaults and const parameters in the same parameter list is currently not permitted -warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes - --> $DIR/wrong-order.rs:2:27 - | -LL | #![cfg_attr(full, feature(const_generics))] - | ^^^^^^^^^^^^^^ - | - = note: `#[warn(incomplete_features)]` on by default - = note: see issue #44580 for more information - -error: aborting due to previous error; 1 warning emitted +error: aborting due to previous error diff --git a/src/test/ui/const-generics/defaults/wrong-order.min.stderr b/src/test/ui/const-generics/defaults/wrong-order.min.stderr index c8f1d471b24..eb0bcb28215 100644 --- a/src/test/ui/const-generics/defaults/wrong-order.min.stderr +++ b/src/test/ui/const-generics/defaults/wrong-order.min.stderr @@ -1,10 +1,8 @@ error: generic parameters with a default must be trailing - --> $DIR/wrong-order.rs:4:10 + --> $DIR/wrong-order.rs:6:10 | LL | struct A { | ^ - | - = note: using type defaults and const parameters in the same parameter list is currently not permitted error: aborting due to previous error diff --git a/src/test/ui/const-generics/defaults/wrong-order.rs b/src/test/ui/const-generics/defaults/wrong-order.rs index 5c2d9b8ad47..88e9e96ba43 100644 --- a/src/test/ui/const-generics/defaults/wrong-order.rs +++ b/src/test/ui/const-generics/defaults/wrong-order.rs @@ -1,5 +1,7 @@ // revisions: full min -#![cfg_attr(full, feature(const_generics))] //[full]~WARN the feature `const_generics` is incomplete +#![cfg_attr(full, feature(const_generics))] +#![feature(const_generics_defaults)] +#![allow(incomplete_features)] struct A { //~^ ERROR generic parameters with a default must be trailing diff --git a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr index d8bfab6aa52..cf947a565c4 100644 --- a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr +++ b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr @@ -1,5 +1,5 @@ error: generic parameters with a default must be trailing - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:12 + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:12 | LL | struct Bar(T); | ^ @@ -7,7 +7,7 @@ LL | struct Bar(T); = note: using type defaults and const parameters in the same parameter list is currently not permitted error[E0128]: generic parameters with a default cannot use forward declared identifiers - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:21 + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:21 | LL | struct Bar(T); | ^ defaulted generic parameters cannot be forward declared diff --git a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr index 44393a30266..4c97012f361 100644 --- a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr +++ b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr @@ -1,5 +1,5 @@ error: generic parameters with a default must be trailing - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:12 + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:12 | LL | struct Bar(T); | ^ @@ -16,7 +16,7 @@ LL | struct Foo()]>(T, U); = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions error[E0128]: generic parameters with a default cannot use forward declared identifiers - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:21 + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:21 | LL | struct Bar(T); | ^ defaulted generic parameters cannot be forward declared diff --git a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs index 8a84afd065c..bf4f9558adc 100644 --- a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs +++ b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs @@ -7,7 +7,6 @@ struct Foo()]>(T, U); //[full]~^ ERROR the size for values of type `T` cannot be known at compilation time //[min]~^^ ERROR generic parameters may not be used in const operations -// FIXME(const_generics_defaults): We still don't know how to deal with type defaults. struct Bar(T); //~^ ERROR generic parameters with a default cannot use forward declared identifiers //~| ERROR generic parameters with a default From 312b4fdfd281a5ebd740acaf88cc82c47225be23 Mon Sep 17 00:00:00 2001 From: lcnr Date: Sun, 18 Apr 2021 15:14:17 +0200 Subject: [PATCH 3/4] improve wf check for const param defaults --- compiler/rustc_typeck/src/check/wfcheck.rs | 53 ++++++++++++++----- .../complex-generic-default-expr.min.stderr | 4 +- .../defaults/complex-generic-default-expr.rs | 8 ++- .../defaults/const-param-as-default-value.rs | 14 +++++ .../defaults/const-param-in-ty-defaults.rs | 18 +++++++ .../defaults/default-param-wf-concrete.rs | 5 ++ .../defaults/default-param-wf-concrete.stderr | 9 ++++ .../defaults/pretty-printing-ast.rs | 1 - 8 files changed, 94 insertions(+), 18 deletions(-) create mode 100644 src/test/ui/const-generics/defaults/const-param-as-default-value.rs create mode 100644 src/test/ui/const-generics/defaults/const-param-in-ty-defaults.rs create mode 100644 src/test/ui/const-generics/defaults/default-param-wf-concrete.rs create mode 100644 src/test/ui/const-generics/defaults/default-param-wf-concrete.stderr diff --git a/compiler/rustc_typeck/src/check/wfcheck.rs b/compiler/rustc_typeck/src/check/wfcheck.rs index 887cc42a1dd..26871d6f028 100644 --- a/compiler/rustc_typeck/src/check/wfcheck.rs +++ b/compiler/rustc_typeck/src/check/wfcheck.rs @@ -728,20 +728,36 @@ fn check_where_clauses<'tcx, 'fcx>( // // Here, the default `Vec<[u32]>` is not WF because `[u32]: Sized` does not hold. for param in &generics.params { - if let GenericParamDefKind::Type { .. } = param.kind { - if is_our_default(¶m) { - let ty = fcx.tcx.type_of(param.def_id); - // Ignore dependent defaults -- that is, where the default of one type - // parameter includes another (e.g., ``). In those cases, we can't - // be sure if it will error or not as user might always specify the other. - if !ty.needs_subst() { + match param.kind { + GenericParamDefKind::Type { .. } => { + if is_our_default(¶m) { + let ty = fcx.tcx.type_of(param.def_id); + // Ignore dependent defaults -- that is, where the default of one type + // parameter includes another (e.g., ``). In those cases, we can't + // be sure if it will error or not as user might always specify the other. + if !ty.needs_subst() { + fcx.register_wf_obligation( + ty.into(), + fcx.tcx.def_span(param.def_id), + ObligationCauseCode::MiscObligation, + ); + } + } + } + GenericParamDefKind::Const { .. } => { + // FIXME(const_generics_defaults): Figure out if this + // is the behavior we want, see the comment further below. + if is_our_default(¶m) { + let default_ct = tcx.const_param_default(param.def_id); fcx.register_wf_obligation( - ty.into(), + default_ct.into(), fcx.tcx.def_span(param.def_id), ObligationCauseCode::MiscObligation, ); } } + // Doesn't have defaults. + GenericParamDefKind::Lifetime => {} } } @@ -774,14 +790,25 @@ fn check_where_clauses<'tcx, 'fcx>( fcx.tcx.mk_param_from_def(param) } GenericParamDefKind::Const { .. } => { + // FIXME(const_generics_defaults): I(@lcnr) feel like always + // using the const parameter is the right choice here, even + // if it needs substs. + // + // Before stabilizing this we probably want to get some tests + // where this makes a difference and figure out what's the exact + // behavior we want here. + + // If the param has a default, ... if is_our_default(param) { let default_ct = tcx.const_param_default(param.def_id); - // Const params currently have to be concrete. - assert!(!default_ct.needs_subst()); - default_ct.into() - } else { - fcx.tcx.mk_param_from_def(param) + // ... and it's not a dependent default, ... + if !default_ct.needs_subst() { + // ... then substitute it with the default. + return default_ct.into(); + } } + + fcx.tcx.mk_param_from_def(param) } } }); diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr b/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr index d50a0a61d49..7d51e9aa0f3 100644 --- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr @@ -1,5 +1,5 @@ error: generic parameters may not be used in const operations - --> $DIR/complex-generic-default-expr.rs:6:47 + --> $DIR/complex-generic-default-expr.rs:10:47 | LL | struct Foo; | ^ cannot perform const operation using `N` @@ -8,7 +8,7 @@ LL | struct Foo; = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions error: generic parameters may not be used in const operations - --> $DIR/complex-generic-default-expr.rs:9:62 + --> $DIR/complex-generic-default-expr.rs:13:62 | LL | struct Bar() }>(T); | ^ cannot perform const operation using `T` diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs index 1c25fda8d30..a1c04b5e7c3 100644 --- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs @@ -1,4 +1,8 @@ -// revisions: full min +// revisions: min +// FIXME(const_generics): add the `full` revision, +// currently causes an ICE as we don't supply substs to +// anon consts in the parameter listing, as that would +// cause that anon const to reference itself. #![cfg_attr(full, feature(const_generics))] #![feature(const_generics_defaults)] #![allow(incomplete_features)] @@ -8,6 +12,6 @@ struct Foo; struct Bar() }>(T); //[min]~^ ERROR generic parameters may not be used in const operations -//[full]~^^ ERROR the size for values of type `T` cannot be known at compilation time +//[full]~^^ ERROR the size for values of type `T` cannot be known at compilation time fn main() {} diff --git a/src/test/ui/const-generics/defaults/const-param-as-default-value.rs b/src/test/ui/const-generics/defaults/const-param-as-default-value.rs new file mode 100644 index 00000000000..d9cab34327e --- /dev/null +++ b/src/test/ui/const-generics/defaults/const-param-as-default-value.rs @@ -0,0 +1,14 @@ +// run-pass +#![feature(const_generics_defaults)] +#![allow(incomplete_features)] +struct Foo([u8; N], [u8; M]); + +fn foo() -> Foo { + let x = [0; N]; + Foo(x, x) +} + +fn main() { + let val = foo::<13>(); + assert_eq!(val.0, val.1); +} diff --git a/src/test/ui/const-generics/defaults/const-param-in-ty-defaults.rs b/src/test/ui/const-generics/defaults/const-param-in-ty-defaults.rs new file mode 100644 index 00000000000..e3d78fe2ee0 --- /dev/null +++ b/src/test/ui/const-generics/defaults/const-param-in-ty-defaults.rs @@ -0,0 +1,18 @@ +// run-pass +#![feature(const_generics_defaults)] +#![allow(incomplete_features)] +// FIXME(const_generics_defaults): while we can allow this, +// we probably won't easily allow this with more complex const operations. +// +// So we have to make a conscious decision here when stabilizing a relaxed parameter ordering. +struct Foo(T); + +impl Foo { + fn new() -> Self { + Foo([0; N]) + } +} + +fn main() { + assert_eq!(Foo::new().0, [0; 10]); +} diff --git a/src/test/ui/const-generics/defaults/default-param-wf-concrete.rs b/src/test/ui/const-generics/defaults/default-param-wf-concrete.rs new file mode 100644 index 00000000000..4bb56c6a1c0 --- /dev/null +++ b/src/test/ui/const-generics/defaults/default-param-wf-concrete.rs @@ -0,0 +1,5 @@ +#![feature(const_generics_defaults)] +#![allow(incomplete_features)] +struct Foo; +//~^ ERROR evaluation of constant value failed +fn main() {} diff --git a/src/test/ui/const-generics/defaults/default-param-wf-concrete.stderr b/src/test/ui/const-generics/defaults/default-param-wf-concrete.stderr new file mode 100644 index 00000000000..8464ea98bf6 --- /dev/null +++ b/src/test/ui/const-generics/defaults/default-param-wf-concrete.stderr @@ -0,0 +1,9 @@ +error[E0080]: evaluation of constant value failed + --> $DIR/default-param-wf-concrete.rs:3:28 + | +LL | struct Foo; + | ^^^^^^^ attempt to compute `u8::MAX + 1_u8`, which would overflow + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0080`. diff --git a/src/test/ui/const-generics/defaults/pretty-printing-ast.rs b/src/test/ui/const-generics/defaults/pretty-printing-ast.rs index 12a92a10476..7a57950dfc9 100644 --- a/src/test/ui/const-generics/defaults/pretty-printing-ast.rs +++ b/src/test/ui/const-generics/defaults/pretty-printing-ast.rs @@ -11,4 +11,3 @@ trait Foo {} fn foo() {} struct Range; - From d3e0d2f53dd69bf10b4260760e5fbaddc77c2a3d Mon Sep 17 00:00:00 2001 From: lcnr Date: Sun, 18 Apr 2021 16:43:43 +0200 Subject: [PATCH 4/4] supply substs to anon consts in defaults --- compiler/rustc_typeck/src/astconv/mod.rs | 4 +- .../rustc_typeck/src/check/fn_ctxt/_impl.rs | 4 +- compiler/rustc_typeck/src/collect.rs | 39 +++++++++---------- .../complex-generic-default-expr.full.stderr | 24 ++++++------ .../complex-generic-default-expr.min.stderr | 4 +- .../defaults/complex-generic-default-expr.rs | 13 +++---- .../defaults/const-param-as-default-value.rs | 9 +++++ .../defaults/const-param-in-ty-defaults.rs | 4 -- ...ms-in-ct-in-ty-param-lazy-norm.full.stderr | 22 ++--------- ...ams-in-ct-in-ty-param-lazy-norm.min.stderr | 6 +-- .../params-in-ct-in-ty-param-lazy-norm.rs | 4 +- 11 files changed, 62 insertions(+), 71 deletions(-) diff --git a/compiler/rustc_typeck/src/astconv/mod.rs b/compiler/rustc_typeck/src/astconv/mod.rs index b6de491911a..62a1584d16b 100644 --- a/compiler/rustc_typeck/src/astconv/mod.rs +++ b/compiler/rustc_typeck/src/astconv/mod.rs @@ -513,7 +513,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { GenericParamDefKind::Const { has_default } => { let ty = tcx.at(self.span).type_of(param.def_id); if !infer_args && has_default { - tcx.const_param_default(param.def_id).into() + tcx.const_param_default(param.def_id) + .subst_spanned(tcx, substs.unwrap(), Some(self.span)) + .into() } else { if infer_args { self.astconv.ct_infer(ty, Some(param), self.span).into() diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs index 9ace4550421..a50f8e1c655 100644 --- a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs +++ b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs @@ -1446,7 +1446,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } GenericParamDefKind::Const { has_default, .. } => { if !infer_args && has_default { - tcx.const_param_default(param.def_id).into() + tcx.const_param_default(param.def_id) + .subst_spanned(tcx, substs.unwrap(), Some(self.span)) + .into() } else { self.fcx.var_for_def(self.span, param) } diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs index 1477418d5d8..927d8c57191 100644 --- a/compiler/rustc_typeck/src/collect.rs +++ b/compiler/rustc_typeck/src/collect.rs @@ -1316,13 +1316,13 @@ fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option Visitor<'v> for AnonConstInParamListDetector { +impl<'v> Visitor<'v> for AnonConstInParamTyDetector { type Map = intravisit::ErasedMap<'v>; fn nested_visit_map(&mut self) -> NestedVisitorMap { @@ -1330,15 +1330,17 @@ impl<'v> Visitor<'v> for AnonConstInParamListDetector { } fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) { - let prev = self.in_param_list; - self.in_param_list = true; - intravisit::walk_generic_param(self, p); - self.in_param_list = prev; + if let GenericParamKind::Const { ref ty, default: _ } = p.kind { + let prev = self.in_param_ty; + self.in_param_ty = true; + self.visit_ty(ty); + self.in_param_ty = prev; + } } fn visit_anon_const(&mut self, c: &'v hir::AnonConst) { - if self.in_param_list && self.ct == c.hir_id { - self.found_anon_const_in_list = true; + if self.in_param_ty && self.ct == c.hir_id { + self.found_anon_const_in_param_ty = true; } else { intravisit::walk_anon_const(self, c) } @@ -1366,27 +1368,24 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics { let parent_id = tcx.hir().get_parent_item(hir_id); let parent_def_id = tcx.hir().local_def_id(parent_id); - let mut in_param_list = false; + let mut in_param_ty = false; for (_parent, node) in tcx.hir().parent_iter(hir_id) { if let Some(generics) = node.generics() { - let mut visitor = AnonConstInParamListDetector { - in_param_list: false, - found_anon_const_in_list: false, + let mut visitor = AnonConstInParamTyDetector { + in_param_ty: false, + found_anon_const_in_param_ty: false, ct: hir_id, }; visitor.visit_generics(generics); - in_param_list = visitor.found_anon_const_in_list; + in_param_ty = visitor.found_anon_const_in_param_ty; break; } } - if in_param_list { + if in_param_ty { // We do not allow generic parameters in anon consts if we are inside - // of a param list. - // - // This affects both default type bindings, e.g. `struct()]>(T, U)`, - // and the types of const parameters, e.g. `struct V();`. + // of a const parameter type, e.g. `struct Foo` is not allowed. None } else if tcx.lazy_normalization() { // HACK(eddyb) this provides the correct generics when diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr b/src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr index c1444abbd3f..e0e2b6c69f2 100644 --- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr @@ -1,16 +1,18 @@ -error[E0277]: the size for values of type `T` cannot be known at compilation time - --> $DIR/complex-generic-default-expr.rs:9:62 +error: constant expression depends on a generic parameter + --> $DIR/complex-generic-default-expr.rs:6:34 + | +LL | struct Foo; + | ^ + | + = note: this may fail depending on what value the parameter takes + +error: constant expression depends on a generic parameter + --> $DIR/complex-generic-default-expr.rs:10:21 | LL | struct Bar() }>(T); - | - ^ doesn't have a size known at compile-time - | | - | this type parameter needs to be `std::marker::Sized` - | - ::: $SRC_DIR/core/src/mem/mod.rs:LL:COL + | ^^^^^^^^^ | -LL | pub const fn size_of() -> usize { - | - required by this bound in `std::mem::size_of` + = note: this may fail depending on what value the parameter takes -error: aborting due to previous error +error: aborting due to 2 previous errors -For more information about this error, try `rustc --explain E0277`. diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr b/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr index 7d51e9aa0f3..58abd8db9f0 100644 --- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr @@ -1,5 +1,5 @@ error: generic parameters may not be used in const operations - --> $DIR/complex-generic-default-expr.rs:10:47 + --> $DIR/complex-generic-default-expr.rs:6:47 | LL | struct Foo; | ^ cannot perform const operation using `N` @@ -8,7 +8,7 @@ LL | struct Foo; = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions error: generic parameters may not be used in const operations - --> $DIR/complex-generic-default-expr.rs:13:62 + --> $DIR/complex-generic-default-expr.rs:10:62 | LL | struct Bar() }>(T); | ^ cannot perform const operation using `T` diff --git a/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs index a1c04b5e7c3..a7b712f7b4b 100644 --- a/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs +++ b/src/test/ui/const-generics/defaults/complex-generic-default-expr.rs @@ -1,17 +1,14 @@ -// revisions: min -// FIXME(const_generics): add the `full` revision, -// currently causes an ICE as we don't supply substs to -// anon consts in the parameter listing, as that would -// cause that anon const to reference itself. +// revisions: full min #![cfg_attr(full, feature(const_generics))] #![feature(const_generics_defaults)] #![allow(incomplete_features)] struct Foo; -//[min]~^ ERROR generic parameters may not be used in const operations +//[full]~^ ERROR constant expression depends on a generic parameter +//[min]~^^ ERROR generic parameters may not be used in const operations struct Bar() }>(T); -//[min]~^ ERROR generic parameters may not be used in const operations -//[full]~^^ ERROR the size for values of type `T` cannot be known at compilation time +//[full]~^ ERROR constant expression depends on a generic parameter +//[min]~^^ ERROR generic parameters may not be used in const operations fn main() {} diff --git a/src/test/ui/const-generics/defaults/const-param-as-default-value.rs b/src/test/ui/const-generics/defaults/const-param-as-default-value.rs index d9cab34327e..59ac261f44f 100644 --- a/src/test/ui/const-generics/defaults/const-param-as-default-value.rs +++ b/src/test/ui/const-generics/defaults/const-param-as-default-value.rs @@ -8,7 +8,16 @@ fn foo() -> Foo { Foo(x, x) } +// To check that we actually apply the correct substs for const param defaults. +fn concrete_foo() -> Foo<13> { + Foo(Default::default(), Default::default()) +} + + fn main() { let val = foo::<13>(); assert_eq!(val.0, val.1); + + let val = concrete_foo(); + assert_eq!(val.0, val.1); } diff --git a/src/test/ui/const-generics/defaults/const-param-in-ty-defaults.rs b/src/test/ui/const-generics/defaults/const-param-in-ty-defaults.rs index e3d78fe2ee0..3f534ca0308 100644 --- a/src/test/ui/const-generics/defaults/const-param-in-ty-defaults.rs +++ b/src/test/ui/const-generics/defaults/const-param-in-ty-defaults.rs @@ -1,10 +1,6 @@ // run-pass #![feature(const_generics_defaults)] #![allow(incomplete_features)] -// FIXME(const_generics_defaults): while we can allow this, -// we probably won't easily allow this with more complex const operations. -// -// So we have to make a conscious decision here when stabilizing a relaxed parameter ordering. struct Foo(T); impl Foo { diff --git a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr index cf947a565c4..e8fd9e7769b 100644 --- a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr +++ b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr @@ -1,5 +1,5 @@ error: generic parameters with a default must be trailing - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:12 + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:8:12 | LL | struct Bar(T); | ^ @@ -7,25 +7,11 @@ LL | struct Bar(T); = note: using type defaults and const parameters in the same parameter list is currently not permitted error[E0128]: generic parameters with a default cannot use forward declared identifiers - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:21 + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:8:21 | LL | struct Bar(T); | ^ defaulted generic parameters cannot be forward declared -error[E0277]: the size for values of type `T` cannot be known at compilation time - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:6:44 - | -LL | struct Foo()]>(T, U); - | - ^ doesn't have a size known at compile-time - | | - | this type parameter needs to be `std::marker::Sized` - | - ::: $SRC_DIR/core/src/mem/mod.rs:LL:COL - | -LL | pub const fn size_of() -> usize { - | - required by this bound in `std::mem::size_of` +error: aborting due to 2 previous errors -error: aborting due to 3 previous errors - -Some errors have detailed explanations: E0128, E0277. -For more information about an error, try `rustc --explain E0128`. +For more information about this error, try `rustc --explain E0128`. diff --git a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr index 4c97012f361..5fa6423306c 100644 --- a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr +++ b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr @@ -1,5 +1,5 @@ error: generic parameters with a default must be trailing - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:12 + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:8:12 | LL | struct Bar(T); | ^ @@ -7,7 +7,7 @@ LL | struct Bar(T); = note: using type defaults and const parameters in the same parameter list is currently not permitted error: generic parameters may not be used in const operations - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:6:44 + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:5:44 | LL | struct Foo()]>(T, U); | ^ cannot perform const operation using `T` @@ -16,7 +16,7 @@ LL | struct Foo()]>(T, U); = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions error[E0128]: generic parameters with a default cannot use forward declared identifiers - --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:21 + --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:8:21 | LL | struct Bar(T); | ^ defaulted generic parameters cannot be forward declared diff --git a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs index bf4f9558adc..76c1b84aef5 100644 --- a/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs +++ b/src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs @@ -1,11 +1,9 @@ // revisions: full min - #![cfg_attr(full, feature(const_generics))] #![cfg_attr(full, allow(incomplete_features))] struct Foo()]>(T, U); -//[full]~^ ERROR the size for values of type `T` cannot be known at compilation time -//[min]~^^ ERROR generic parameters may not be used in const operations +//[min]~^ ERROR generic parameters may not be used in const operations struct Bar(T); //~^ ERROR generic parameters with a default cannot use forward declared identifiers