Rollup merge of #69901 - RalfJung:rustc_layout, r=eddyb
add #[rustc_layout(debug)] @eddyb recently told me about the `#[rustc_layout]` attribute, and I think it would be very useful if it could be used to print all the layout information Rust has about a type. When working with layouts (e.g. in Miri), it is often not clear how certain surface language features get represented internally. I have some awful hacks locally to be able to dump this debug information; with this attribute I could get it on the playground which is so much better. :)
This commit is contained in:
Dylan DPC
GitHub
commit
fd3f9176c3
4 changed files with 356 additions and 8 deletions
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@ -17,32 +17,38 @@ use rustc_span::symbol::sym;
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pub fn test_layout(tcx: TyCtxt<'_>) {
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if tcx.features().rustc_attrs {
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// if the `rustc_attrs` feature is not enabled, don't bother testing layout
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tcx.hir().krate().visit_all_item_likes(&mut VarianceTest { tcx });
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tcx.hir().krate().visit_all_item_likes(&mut LayoutTest { tcx });
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}
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}
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struct VarianceTest<'tcx> {
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struct LayoutTest<'tcx> {
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tcx: TyCtxt<'tcx>,
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}
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impl ItemLikeVisitor<'tcx> for VarianceTest<'tcx> {
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impl ItemLikeVisitor<'tcx> for LayoutTest<'tcx> {
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fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
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let item_def_id = self.tcx.hir().local_def_id(item.hir_id);
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if let ItemKind::TyAlias(..) = item.kind {
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match item.kind {
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ItemKind::TyAlias(..)
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| ItemKind::Enum(..)
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| ItemKind::Struct(..)
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| ItemKind::Union(..) => {
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for attr in self.tcx.get_attrs(item_def_id).iter() {
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if attr.check_name(sym::rustc_layout) {
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self.dump_layout_of(item_def_id, item, attr);
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}
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}
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}
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_ => {}
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}
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}
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fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem<'tcx>) {}
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fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem<'tcx>) {}
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}
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impl VarianceTest<'tcx> {
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impl LayoutTest<'tcx> {
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fn dump_layout_of(&self, item_def_id: DefId, item: &hir::Item<'tcx>, attr: &Attribute) {
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let tcx = self.tcx;
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let param_env = self.tcx.param_env(item_def_id);
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@ -81,6 +87,13 @@ impl VarianceTest<'tcx> {
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);
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}
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sym::debug => {
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self.tcx.sess.span_err(
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item.span,
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&format!("layout debugging: {:#?}", *ty_layout),
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);
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}
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name => {
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self.tcx.sess.span_err(
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meta_item.span(),
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@ -253,6 +253,7 @@ symbols! {
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debug_trait,
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declare_lint_pass,
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decl_macro,
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debug,
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Debug,
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Decodable,
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Default,
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15
src/test/ui/layout/debug.rs
Normal file
15
src/test/ui/layout/debug.rs
Normal file
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@ -0,0 +1,15 @@
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// normalize-stderr-test "pref: Align \{\n *pow2: [1-3],\n *\}" -> "pref: $$PREF_ALIGN"
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#![feature(never_type, rustc_attrs)]
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#![crate_type = "lib"]
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#[rustc_layout(debug)]
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enum E { Foo, Bar(!, i32, i32) } //~ ERROR: layout debugging
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#[rustc_layout(debug)]
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struct S { f1: i32, f2: (), f3: i32 } //~ ERROR: layout debugging
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#[rustc_layout(debug)]
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union U { f1: (i32, i32), f3: i32 } //~ ERROR: layout debugging
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#[rustc_layout(debug)]
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type Test = Result<i32, i32>; //~ ERROR: layout debugging
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319
src/test/ui/layout/debug.stderr
Normal file
319
src/test/ui/layout/debug.stderr
Normal file
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@ -0,0 +1,319 @@
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error: layout debugging: LayoutDetails {
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fields: Arbitrary {
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offsets: [
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Size {
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raw: 0,
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},
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],
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memory_index: [
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0,
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],
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},
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variants: Multiple {
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discr: Scalar {
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value: Int(
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I32,
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false,
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),
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valid_range: 0..=0,
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},
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discr_kind: Tag,
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discr_index: 0,
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variants: [
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LayoutDetails {
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fields: Arbitrary {
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offsets: [],
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memory_index: [],
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},
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variants: Single {
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index: 0,
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},
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abi: Aggregate {
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sized: true,
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},
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largest_niche: None,
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align: AbiAndPrefAlign {
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abi: Align {
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pow2: 0,
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},
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pref: $PREF_ALIGN,
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},
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size: Size {
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raw: 4,
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},
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},
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LayoutDetails {
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fields: Arbitrary {
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offsets: [
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Size {
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raw: 4,
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},
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Size {
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raw: 4,
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},
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Size {
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raw: 8,
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},
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],
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memory_index: [
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0,
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1,
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2,
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],
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},
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variants: Single {
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index: 1,
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},
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abi: Uninhabited,
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largest_niche: None,
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align: AbiAndPrefAlign {
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abi: Align {
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pow2: 2,
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},
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pref: $PREF_ALIGN,
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},
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size: Size {
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raw: 12,
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},
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},
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],
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},
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abi: Aggregate {
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sized: true,
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},
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largest_niche: Some(
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Niche {
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offset: Size {
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raw: 0,
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},
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scalar: Scalar {
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value: Int(
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I32,
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false,
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),
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valid_range: 0..=0,
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},
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},
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),
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align: AbiAndPrefAlign {
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abi: Align {
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pow2: 2,
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},
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pref: $PREF_ALIGN,
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},
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size: Size {
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raw: 12,
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},
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}
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--> $DIR/debug.rs:6:1
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LL | enum E { Foo, Bar(!, i32, i32) }
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: layout debugging: LayoutDetails {
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fields: Arbitrary {
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offsets: [
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Size {
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raw: 0,
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},
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Size {
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raw: 0,
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},
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Size {
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raw: 4,
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},
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],
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memory_index: [
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1,
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0,
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2,
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],
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},
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variants: Single {
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index: 0,
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},
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abi: ScalarPair(
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Scalar {
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value: Int(
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I32,
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true,
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),
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valid_range: 0..=4294967295,
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},
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Scalar {
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value: Int(
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I32,
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true,
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),
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valid_range: 0..=4294967295,
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},
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),
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largest_niche: None,
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align: AbiAndPrefAlign {
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abi: Align {
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pow2: 2,
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},
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pref: $PREF_ALIGN,
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},
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size: Size {
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raw: 8,
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},
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}
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--> $DIR/debug.rs:9:1
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LL | struct S { f1: i32, f2: (), f3: i32 }
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: layout debugging: LayoutDetails {
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fields: Union(
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2,
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),
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variants: Single {
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index: 0,
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},
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abi: Aggregate {
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sized: true,
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},
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largest_niche: None,
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align: AbiAndPrefAlign {
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abi: Align {
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pow2: 2,
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},
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pref: $PREF_ALIGN,
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},
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size: Size {
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raw: 8,
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},
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}
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--> $DIR/debug.rs:12:1
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LL | union U { f1: (i32, i32), f3: i32 }
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: layout debugging: LayoutDetails {
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fields: Arbitrary {
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offsets: [
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Size {
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raw: 0,
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},
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],
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memory_index: [
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0,
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],
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},
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variants: Multiple {
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discr: Scalar {
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value: Int(
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I32,
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false,
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),
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valid_range: 0..=1,
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},
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discr_kind: Tag,
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discr_index: 0,
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variants: [
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LayoutDetails {
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fields: Arbitrary {
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offsets: [
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Size {
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raw: 4,
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},
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],
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memory_index: [
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0,
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],
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},
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variants: Single {
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index: 0,
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},
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abi: Aggregate {
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sized: true,
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},
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largest_niche: None,
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align: AbiAndPrefAlign {
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abi: Align {
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pow2: 2,
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},
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pref: $PREF_ALIGN,
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},
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size: Size {
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raw: 8,
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},
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},
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LayoutDetails {
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fields: Arbitrary {
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offsets: [
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Size {
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raw: 4,
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},
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],
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memory_index: [
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0,
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],
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},
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variants: Single {
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index: 1,
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},
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abi: Aggregate {
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sized: true,
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},
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largest_niche: None,
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align: AbiAndPrefAlign {
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abi: Align {
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pow2: 2,
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},
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pref: $PREF_ALIGN,
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},
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size: Size {
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raw: 8,
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},
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},
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],
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},
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abi: ScalarPair(
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Scalar {
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value: Int(
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I32,
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false,
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),
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valid_range: 0..=1,
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},
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Scalar {
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value: Int(
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I32,
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true,
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),
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valid_range: 0..=4294967295,
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},
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),
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largest_niche: Some(
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Niche {
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offset: Size {
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raw: 0,
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},
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scalar: Scalar {
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value: Int(
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I32,
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false,
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),
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valid_range: 0..=1,
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},
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},
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),
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align: AbiAndPrefAlign {
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abi: Align {
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pow2: 2,
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},
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pref: $PREF_ALIGN,
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},
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size: Size {
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raw: 8,
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},
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}
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--> $DIR/debug.rs:15:1
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LL | type Test = Result<i32, i32>;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to 4 previous errors
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