Rollup merge of #74487 - lcnr:const-in-ty-default, r=varkor
Forbid generic parameters in anon consts inside of type defaults Emit a resolution error for `struct Foo<T, U = [u8; std::mem::size_of::<T>()]>`. We are unable to support this with the way `ty::Generics` is currently used, so let's just forbid it entirely for now. Fixes some ICE on stable, e.g. ```rust struct Foo<T, U = [u8; std::mem::size_of::<*mut T>()]>(T, U); ``` r? @varkor @eddyb
This commit is contained in:
Manish Goregaokar
GitHub
commit
e0543409d5
7 changed files with 135 additions and 13 deletions
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@ -442,7 +442,7 @@ impl<'a> Resolver<'a> {
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);
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err
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}
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ResolutionError::ParamInTyOfConstArg(name) => {
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ResolutionError::ParamInTyOfConstParam(name) => {
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let mut err = struct_span_err!(
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self.session,
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span,
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@ -455,6 +455,17 @@ impl<'a> Resolver<'a> {
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);
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err
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}
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ResolutionError::ParamInAnonConstInTyDefault(name) => {
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let mut err = self.session.struct_span_err(
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span,
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"constant values inside of type parameter defaults must not depend on generic parameters",
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);
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err.span_label(
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span,
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format!("the anonymous constant must not depend on the parameter `{}`", name),
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);
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err
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}
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ResolutionError::SelfInTyParamDefault => {
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let mut err = struct_span_err!(
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self.session,
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@ -570,7 +570,15 @@ impl<'a, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
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if let Some(ref ty) = default {
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self.ribs[TypeNS].push(default_ban_rib);
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self.visit_ty(ty);
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self.with_rib(ValueNS, ForwardTyParamBanRibKind, |this| {
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// HACK: We use an empty `ForwardTyParamBanRibKind` here which
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// is only used to forbid the use of const parameters inside of
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// type defaults.
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//
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// While the rib name doesn't really fit here, it does allow us to use the same
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// code for both const and type parameters.
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this.visit_ty(ty);
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});
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default_ban_rib = self.ribs[TypeNS].pop().unwrap();
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}
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@ -1081,7 +1089,9 @@ impl<'a, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
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fn with_constant_rib(&mut self, f: impl FnOnce(&mut Self)) {
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debug!("with_constant_rib");
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self.with_rib(ValueNS, ConstantItemRibKind, |this| {
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this.with_label_rib(ConstantItemRibKind, f);
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this.with_rib(TypeNS, ConstantItemRibKind, |this| {
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this.with_label_rib(ConstantItemRibKind, f);
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})
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});
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}
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@ -215,7 +215,9 @@ enum ResolutionError<'a> {
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/// Error E0128: type parameters with a default cannot use forward-declared identifiers.
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ForwardDeclaredTyParam, // FIXME(const_generics:defaults)
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/// ERROR E0770: the type of const parameters must not depend on other generic parameters.
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ParamInTyOfConstArg(Symbol),
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ParamInTyOfConstParam(Symbol),
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/// constant values inside of type parameter defaults must not depend on generic parameters.
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ParamInAnonConstInTyDefault(Symbol),
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/// Error E0735: type parameters with a default cannot use `Self`
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SelfInTyParamDefault,
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/// Error E0767: use of unreachable label
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@ -2514,7 +2516,7 @@ impl<'a> Resolver<'a> {
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}
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ConstParamTyRibKind => {
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if record_used {
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self.report_error(span, ParamInTyOfConstArg(rib_ident.name));
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self.report_error(span, ParamInTyOfConstParam(rib_ident.name));
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}
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return Res::Err;
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}
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@ -2526,18 +2528,40 @@ impl<'a> Resolver<'a> {
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}
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}
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Res::Def(DefKind::TyParam, _) | Res::SelfTy(..) => {
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let mut in_ty_param_default = false;
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for rib in ribs {
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let has_generic_params = match rib.kind {
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NormalRibKind
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| ClosureOrAsyncRibKind
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| AssocItemRibKind
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| ModuleRibKind(..)
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| MacroDefinition(..)
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| ForwardTyParamBanRibKind
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| ConstantItemRibKind => {
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| MacroDefinition(..) => {
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// Nothing to do. Continue.
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continue;
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}
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// We only forbid constant items if we are inside of type defaults,
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// for example `struct Foo<T, U = [u8; std::mem::size_of::<T>()]>`
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ForwardTyParamBanRibKind => {
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in_ty_param_default = true;
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continue;
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}
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ConstantItemRibKind => {
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if in_ty_param_default {
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if record_used {
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self.report_error(
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span,
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ResolutionError::ParamInAnonConstInTyDefault(
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rib_ident.name,
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),
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);
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}
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return Res::Err;
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} else {
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continue;
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}
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}
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// This was an attempt to use a type parameter outside its scope.
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ItemRibKind(has_generic_params) => has_generic_params,
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FnItemRibKind => HasGenericParams::Yes,
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@ -2545,7 +2569,7 @@ impl<'a> Resolver<'a> {
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if record_used {
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self.report_error(
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span,
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ResolutionError::ParamInTyOfConstArg(rib_ident.name),
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ResolutionError::ParamInTyOfConstParam(rib_ident.name),
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);
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}
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return Res::Err;
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@ -2572,22 +2596,45 @@ impl<'a> Resolver<'a> {
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// (spuriously) conflicting with the const param.
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ribs.next();
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}
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let mut in_ty_param_default = false;
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for rib in ribs {
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let has_generic_params = match rib.kind {
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NormalRibKind
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| ClosureOrAsyncRibKind
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| AssocItemRibKind
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| ModuleRibKind(..)
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| MacroDefinition(..)
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| ForwardTyParamBanRibKind
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| ConstantItemRibKind => continue,
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| MacroDefinition(..) => continue,
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// We only forbid constant items if we are inside of type defaults,
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// for example `struct Foo<T, U = [u8; std::mem::size_of::<T>()]>`
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ForwardTyParamBanRibKind => {
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in_ty_param_default = true;
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continue;
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}
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ConstantItemRibKind => {
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if in_ty_param_default {
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if record_used {
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self.report_error(
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span,
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ResolutionError::ParamInAnonConstInTyDefault(
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rib_ident.name,
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),
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);
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}
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return Res::Err;
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} else {
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continue;
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}
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}
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ItemRibKind(has_generic_params) => has_generic_params,
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FnItemRibKind => HasGenericParams::Yes,
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ConstParamTyRibKind => {
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if record_used {
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self.report_error(
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span,
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ResolutionError::ParamInTyOfConstArg(rib_ident.name),
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ResolutionError::ParamInTyOfConstParam(rib_ident.name),
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);
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}
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return Res::Err;
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@ -0,0 +1,11 @@
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#![feature(const_generics)] //~ WARN the feature `const_generics` is incomplete
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struct Foo<T, U = [u8; std::mem::size_of::<T>()]>(T, U);
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//~^ ERROR constant values inside of type parameter defaults
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// FIXME(const_generics:defaults): We still don't know how to we deal with type defaults.
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struct Bar<T = [u8; N], const N: usize>(T);
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//~^ ERROR constant values inside of type parameter defaults
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//~| ERROR type parameters with a default
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fn main() {}
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@ -0,0 +1,31 @@
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error: type parameters with a default must be trailing
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--> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:7:12
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LL | struct Bar<T = [u8; N], const N: usize>(T);
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| ^
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= note: using type defaults and const parameters in the same parameter list is currently not permitted
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error: constant values inside of type parameter defaults must not depend on generic parameters
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--> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:3:44
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LL | struct Foo<T, U = [u8; std::mem::size_of::<T>()]>(T, U);
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| ^ the anonymous constant must not depend on the parameter `T`
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error: constant values inside of type parameter defaults must not depend on generic parameters
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--> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:7:21
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LL | struct Bar<T = [u8; N], const N: usize>(T);
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| ^ the anonymous constant must not depend on the parameter `N`
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warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
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--> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:1:12
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LL | #![feature(const_generics)]
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| ^^^^^^^^^^^^^^
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= note: `#[warn(incomplete_features)]` on by default
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= note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
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error: aborting due to 3 previous errors; 1 warning emitted
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4
src/test/ui/generic/param-in-ct-in-ty-param-default.rs
Normal file
4
src/test/ui/generic/param-in-ct-in-ty-param-default.rs
Normal file
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@ -0,0 +1,4 @@
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struct Foo<T, U = [u8; std::mem::size_of::<T>()]>(T, U);
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//~^ ERROR constant values inside of type parameter defaults
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fn main() {}
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@ -0,0 +1,8 @@
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error: constant values inside of type parameter defaults must not depend on generic parameters
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--> $DIR/param-in-ct-in-ty-param-default.rs:1:44
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LL | struct Foo<T, U = [u8; std::mem::size_of::<T>()]>(T, U);
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| ^ the anonymous constant must not depend on the parameter `T`
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error: aborting due to previous error
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