Rollup merge of #142570 - jieyouxu:disunion, r=estebank
Reject union default field values Fixes rust-lang/rust#142555. The [`default_field_values` RFC][rfc] does not specify that default field values may be used on `union`s, and it's not clear how default field values may be used with `union`s without an design extension to the RFC. So, for now, reject trying to use default field values with `union`s. ### Review notes - The first commit adds the `union` with default field values test case to `tests/ui/structs/default-field-values/failures.rs`, where `union`s with default field values are currently accepted. - The second commit rejects trying to supply default field values to `union` definitions. - When `default_field_values` feature gate is disabled, we show the feature gate error when the user tries to write `union`s with default field values. When the feature gate is enabled, we reject this usage with > unions cannot have default field values ``@rustbot`` label: +F-default_field_values [rfc]: https://rust-lang.github.io/rfcs/3681-default-field-values.html
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d4f23cdc91
7 changed files with 115 additions and 36 deletions
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@ -179,6 +179,8 @@ ast_lowering_underscore_expr_lhs_assign =
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in expressions, `_` can only be used on the left-hand side of an assignment
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.label = `_` not allowed here
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ast_lowering_union_default_field_values = unions cannot have default field values
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ast_lowering_unstable_inline_assembly = inline assembly is not stable yet on this architecture
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ast_lowering_unstable_inline_assembly_label_operand_with_outputs =
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using both label and output operands for inline assembly is unstable
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@ -475,3 +475,10 @@ pub(crate) struct UseConstGenericArg {
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#[suggestion_part(code = "{other_args}")]
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pub call_args: Span,
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}
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#[derive(Diagnostic)]
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#[diag(ast_lowering_union_default_field_values)]
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pub(crate) struct UnionWithDefault {
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#[primary_span]
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pub span: Span,
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}
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@ -17,6 +17,7 @@ use tracing::instrument;
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use super::errors::{
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InvalidAbi, InvalidAbiSuggestion, MisplacedRelaxTraitBound, TupleStructWithDefault,
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UnionWithDefault,
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};
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use super::stability::{enabled_names, gate_unstable_abi};
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use super::{
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@ -316,7 +317,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
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ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
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|this| {
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this.arena.alloc_from_iter(
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enum_definition.variants.iter().map(|x| this.lower_variant(x)),
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enum_definition.variants.iter().map(|x| this.lower_variant(i, x)),
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)
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},
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);
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@ -328,7 +329,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
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generics,
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id,
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ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
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|this| this.lower_variant_data(hir_id, struct_def),
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|this| this.lower_variant_data(hir_id, i, struct_def),
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);
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hir::ItemKind::Struct(ident, generics, struct_def)
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}
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@ -338,7 +339,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
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generics,
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id,
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ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
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|this| this.lower_variant_data(hir_id, vdata),
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|this| this.lower_variant_data(hir_id, i, vdata),
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);
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hir::ItemKind::Union(ident, generics, vdata)
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}
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@ -714,13 +715,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
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}
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}
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fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
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fn lower_variant(&mut self, item_kind: &ItemKind, v: &Variant) -> hir::Variant<'hir> {
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let hir_id = self.lower_node_id(v.id);
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self.lower_attrs(hir_id, &v.attrs, v.span);
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hir::Variant {
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hir_id,
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def_id: self.local_def_id(v.id),
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data: self.lower_variant_data(hir_id, &v.data),
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data: self.lower_variant_data(hir_id, item_kind, &v.data),
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disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const_to_anon_const(e)),
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ident: self.lower_ident(v.ident),
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span: self.lower_span(v.span),
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@ -730,15 +731,36 @@ impl<'hir> LoweringContext<'_, 'hir> {
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fn lower_variant_data(
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&mut self,
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parent_id: hir::HirId,
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item_kind: &ItemKind,
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vdata: &VariantData,
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) -> hir::VariantData<'hir> {
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match vdata {
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VariantData::Struct { fields, recovered } => hir::VariantData::Struct {
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fields: self
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VariantData::Struct { fields, recovered } => {
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let fields = self
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.arena
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.alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_field_def(f))),
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recovered: *recovered,
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},
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.alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_field_def(f)));
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if let ItemKind::Union(..) = item_kind {
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for field in &fields[..] {
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if let Some(default) = field.default {
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// Unions cannot derive `Default`, and it's not clear how to use default
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// field values of unions if that was supported. Therefore, blanket reject
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// trying to use field values with unions.
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if self.tcx.features().default_field_values() {
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self.dcx().emit_err(UnionWithDefault { span: default.span });
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} else {
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let _ = self.dcx().span_delayed_bug(
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default.span,
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"expected union default field values feature gate error but none \
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was produced",
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);
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}
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}
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}
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}
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hir::VariantData::Struct { fields, recovered: *recovered }
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}
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VariantData::Tuple(fields, id) => {
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let ctor_id = self.lower_node_id(*id);
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self.alias_attrs(ctor_id, parent_id);
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@ -58,6 +58,16 @@ pub enum OptEnum {
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}
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}
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// Default field values may not be used on `union`s (at least, this is not described in the accepted
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// RFC, and it's not currently clear how to extend the design to do so). We emit a feature gate
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// error when the feature is not enabled, but syntactically reject default field values when used
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// with unions when the feature is enabled. This can be adjusted if there's an acceptable design
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// extension, or just unconditionally reject always.
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union U {
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x: i32 = 0, //~ ERROR default values on fields are experimental
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y: f32 = 0.0, //~ ERROR default values on fields are experimental
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}
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fn main () {
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let x = Foo { .. }; //~ ERROR base expression required after `..`
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let y = Foo::default();
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@ -124,8 +124,28 @@ LL | optional: () = (),
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= help: add `#![feature(default_field_values)]` to the crate attributes to enable
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= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
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error[E0658]: default values on fields are experimental
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--> $DIR/feature-gate-default-field-values.rs:67:11
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LL | x: i32 = 0,
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| ^^^^
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= note: see issue #132162 <https://github.com/rust-lang/rust/issues/132162> for more information
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= help: add `#![feature(default_field_values)]` to the crate attributes to enable
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= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
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error[E0658]: default values on fields are experimental
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--> $DIR/feature-gate-default-field-values.rs:68:11
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LL | y: f32 = 0.0,
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| ^^^^^^
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|
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= note: see issue #132162 <https://github.com/rust-lang/rust/issues/132162> for more information
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= help: add `#![feature(default_field_values)]` to the crate attributes to enable
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= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:62:21
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--> $DIR/feature-gate-default-field-values.rs:72:21
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LL | let x = Foo { .. };
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| ^
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@ -140,7 +160,7 @@ LL | let x = Foo { ../* expr */ };
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:64:29
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--> $DIR/feature-gate-default-field-values.rs:74:29
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LL | let z = Foo { baz: 1, .. };
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| ^
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@ -155,7 +175,7 @@ LL | let z = Foo { baz: 1, ../* expr */ };
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:70:26
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--> $DIR/feature-gate-default-field-values.rs:80:26
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|
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LL | let x = Bar::Foo { .. };
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| ^
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@ -170,7 +190,7 @@ LL | let x = Bar::Foo { ../* expr */ };
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:72:34
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--> $DIR/feature-gate-default-field-values.rs:82:34
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LL | let z = Bar::Foo { baz: 1, .. };
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| ^
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@ -185,7 +205,7 @@ LL | let z = Bar::Foo { baz: 1, ../* expr */ };
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:78:31
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--> $DIR/feature-gate-default-field-values.rs:88:31
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|
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LL | let x = Qux::<i32, 4> { .. };
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| ^
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@ -200,7 +220,7 @@ LL | let x = Qux::<i32, 4> { ../* expr */ };
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:79:73
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--> $DIR/feature-gate-default-field-values.rs:89:73
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LL | assert!(matches!(Qux::<i32, 4> { bar: S, baz: 42, bat: 2, bay: 4, .. }, x));
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| ^
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@ -215,7 +235,7 @@ LL | assert!(matches!(Qux::<i32, 4> { bar: S, baz: 42, bat: 2, bay: 4, ../*
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:82:38
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--> $DIR/feature-gate-default-field-values.rs:92:38
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|
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LL | let y = Opt { mandatory: None, .. };
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| ^
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@ -230,7 +250,7 @@ LL | let y = Opt { mandatory: None, ../* expr */ };
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:86:47
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--> $DIR/feature-gate-default-field-values.rs:96:47
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|
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LL | assert!(matches!(Opt { mandatory: None, .. }, z));
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| ^
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@ -245,7 +265,7 @@ LL | assert!(matches!(Opt { mandatory: None, ../* expr */ }, z));
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:88:30
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--> $DIR/feature-gate-default-field-values.rs:98:30
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|
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LL | assert!(matches!(Opt { .. }, z));
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| ^
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@ -256,7 +276,7 @@ LL | assert!(matches!(Opt { ../* expr */ }, z));
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:90:44
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--> $DIR/feature-gate-default-field-values.rs:100:44
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|
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LL | assert!(matches!(Opt { optional: (), .. }, z));
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| ^
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|
|
@ -267,7 +287,7 @@ LL | assert!(matches!(Opt { optional: (), ../* expr */ }, z));
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:92:61
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--> $DIR/feature-gate-default-field-values.rs:102:61
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|
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LL | assert!(matches!(Opt { optional: (), mandatory: None, .. }, z));
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| ^
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@ -279,7 +299,7 @@ LL + assert!(matches!(Opt { optional: (), mandatory: None, }, z));
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|
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:94:51
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--> $DIR/feature-gate-default-field-values.rs:104:51
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|
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LL | let y = OptEnum::Variant { mandatory: None, .. };
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| ^
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|
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@ -294,7 +314,7 @@ LL | let y = OptEnum::Variant { mandatory: None, ../* expr */ };
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| ++++++++++
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|
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:98:60
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--> $DIR/feature-gate-default-field-values.rs:108:60
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|
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LL | assert!(matches!(OptEnum::Variant { mandatory: None, .. }, z));
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| ^
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|
|
@ -309,7 +329,7 @@ LL | assert!(matches!(OptEnum::Variant { mandatory: None, ../* expr */ }, z)
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:100:43
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--> $DIR/feature-gate-default-field-values.rs:110:43
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|
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LL | assert!(matches!(OptEnum::Variant { .. }, z));
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| ^
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|
|
@ -320,7 +340,7 @@ LL | assert!(matches!(OptEnum::Variant { ../* expr */ }, z));
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| ++++++++++
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error[E0797]: base expression required after `..`
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--> $DIR/feature-gate-default-field-values.rs:102:57
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--> $DIR/feature-gate-default-field-values.rs:112:57
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|
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LL | assert!(matches!(OptEnum::Variant { optional: (), .. }, z));
|
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| ^
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|
|
@ -331,7 +351,7 @@ LL | assert!(matches!(OptEnum::Variant { optional: (), ../* expr */ }, z));
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| ++++++++++
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error[E0797]: base expression required after `..`
|
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--> $DIR/feature-gate-default-field-values.rs:104:74
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--> $DIR/feature-gate-default-field-values.rs:114:74
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|
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LL | assert!(matches!(OptEnum::Variant { optional: (), mandatory: None, .. }, z));
|
||||
| ^
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|
|
@ -342,7 +362,7 @@ LL - assert!(matches!(OptEnum::Variant { optional: (), mandatory: None, .. }
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LL + assert!(matches!(OptEnum::Variant { optional: (), mandatory: None, }, z));
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|
|
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error: aborting due to 29 previous errors
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error: aborting due to 31 previous errors
|
||||
|
||||
Some errors have detailed explanations: E0658, E0797.
|
||||
For more information about an error, try `rustc --explain E0658`.
|
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|
|
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|
|
@ -49,6 +49,12 @@ enum E {
|
|||
Variant {} //~ ERROR the `#[default]` attribute may only be used on unit enum variants
|
||||
}
|
||||
|
||||
union U
|
||||
{
|
||||
x: i32 = 1, //~ ERROR unions cannot have default field values
|
||||
y: f32 = 2., //~ ERROR unions cannot have default field values
|
||||
}
|
||||
|
||||
fn main () {
|
||||
let _ = Foo { .. }; // ok
|
||||
let _ = Foo::default(); // ok
|
||||
|
|
|
|||
|
|
@ -12,6 +12,18 @@ error: default fields are not supported in tuple structs
|
|||
LL | pub struct Rak(i32 = 42);
|
||||
| ^^ default fields are only supported on structs
|
||||
|
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error: unions cannot have default field values
|
||||
--> $DIR/failures.rs:54:14
|
||||
|
|
||||
LL | x: i32 = 1,
|
||||
| ^
|
||||
|
||||
error: unions cannot have default field values
|
||||
--> $DIR/failures.rs:55:14
|
||||
|
|
||||
LL | y: f32 = 2.,
|
||||
| ^^
|
||||
|
||||
error[E0277]: the trait bound `S: Default` is not satisfied
|
||||
--> $DIR/failures.rs:16:5
|
||||
|
|
||||
|
|
@ -28,19 +40,19 @@ LL | pub struct S;
|
|||
|
|
||||
|
||||
error: missing field `bar` in initializer
|
||||
--> $DIR/failures.rs:55:19
|
||||
--> $DIR/failures.rs:61:19
|
||||
|
|
||||
LL | let _ = Bar { .. };
|
||||
| ^ fields that do not have a defaulted value must be provided explicitly
|
||||
|
||||
error: missing field `bar` in initializer
|
||||
--> $DIR/failures.rs:56:27
|
||||
--> $DIR/failures.rs:62:27
|
||||
|
|
||||
LL | let _ = Bar { baz: 0, .. };
|
||||
| ^ fields that do not have a defaulted value must be provided explicitly
|
||||
|
||||
error[E0308]: mismatched types
|
||||
--> $DIR/failures.rs:60:17
|
||||
--> $DIR/failures.rs:66:17
|
||||
|
|
||||
LL | let _ = Rak(..);
|
||||
| --- ^^ expected `i32`, found `RangeFull`
|
||||
|
|
@ -53,19 +65,19 @@ note: tuple struct defined here
|
|||
LL | pub struct Rak(i32 = 42);
|
||||
| ^^^
|
||||
help: you might have meant to use `..` to skip providing a value for expected fields, but this is only supported on non-tuple struct literals; it is instead interpreted as a `std::ops::RangeFull` literal
|
||||
--> $DIR/failures.rs:60:17
|
||||
--> $DIR/failures.rs:66:17
|
||||
|
|
||||
LL | let _ = Rak(..);
|
||||
| ^^
|
||||
|
||||
error[E0061]: this struct takes 1 argument but 2 arguments were supplied
|
||||
--> $DIR/failures.rs:62:13
|
||||
--> $DIR/failures.rs:68:13
|
||||
|
|
||||
LL | let _ = Rak(0, ..);
|
||||
| ^^^ -- unexpected argument #2 of type `RangeFull`
|
||||
|
|
||||
help: you might have meant to use `..` to skip providing a value for expected fields, but this is only supported on non-tuple struct literals; it is instead interpreted as a `std::ops::RangeFull` literal
|
||||
--> $DIR/failures.rs:62:20
|
||||
--> $DIR/failures.rs:68:20
|
||||
|
|
||||
LL | let _ = Rak(0, ..);
|
||||
| ^^
|
||||
|
|
@ -81,13 +93,13 @@ LL + let _ = Rak(0);
|
|||
|
|
||||
|
||||
error[E0061]: this struct takes 1 argument but 2 arguments were supplied
|
||||
--> $DIR/failures.rs:64:13
|
||||
--> $DIR/failures.rs:70:13
|
||||
|
|
||||
LL | let _ = Rak(.., 0);
|
||||
| ^^^ -- unexpected argument #1 of type `RangeFull`
|
||||
|
|
||||
help: you might have meant to use `..` to skip providing a value for expected fields, but this is only supported on non-tuple struct literals; it is instead interpreted as a `std::ops::RangeFull` literal
|
||||
--> $DIR/failures.rs:64:17
|
||||
--> $DIR/failures.rs:70:17
|
||||
|
|
||||
LL | let _ = Rak(.., 0);
|
||||
| ^^
|
||||
|
|
@ -102,7 +114,7 @@ LL - let _ = Rak(.., 0);
|
|||
LL + let _ = Rak(0);
|
||||
|
|
||||
|
||||
error: aborting due to 8 previous errors
|
||||
error: aborting due to 10 previous errors
|
||||
|
||||
Some errors have detailed explanations: E0061, E0277, E0308.
|
||||
For more information about an error, try `rustc --explain E0061`.
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue