Commit 6a64501

dingxiangfei2009 dingxiangfei2009

committed

do not materialise X in [X; 0] when X is unsizing a const

1 parent fce0e74 commit 6a64501Copy full SHA for 6a64501

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2 files changed

+50

-1

lines changed

compiler/rustc_mir_build/src/builder/expr
- as_rvalue.rs
tests/ui/coercion
- issue-143671.rs

2 files changed

+50

-1

lines changed

`‎compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs`

Lines changed: 20 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -8,6 +8,7 @@ use rustc_middle::middle::region;`
`8`	`8`	`use rustc_middle::mir::interpret::Scalar;`
`9`	`9`	`use rustc_middle::mir::*;`
`10`	`10`	`use rustc_middle::thir::*;`
	`11`	`+use rustc_middle::ty::adjustment::PointerCoercion;`
`11`	`12`	`use rustc_middle::ty::cast::{CastTy, mir_cast_kind};`
`12`	`13`	`use rustc_middle::ty::util::IntTypeExt;`
`13`	`14`	`use rustc_middle::ty::{self, Ty, UpvarArgs};`
`@@ -656,6 +657,24 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {`
`656`	`657`	`block.and(rvalue)`
`657`	`658`	`}`
`658`	`659`
	`660`	`+ /// Recursively inspect a THIR expression and probe through unsizing`
	`661`	`+ /// operations that can be const-folded today.`
	`662`	`+ fn check_constness(&self, mut ek: &'a ExprKind<'tcx>) -> bool {`
	`663`	`+ loop {`
	`664`	`+ match ek {`
	`665`	`+ &ExprKind::PointerCoercion {`
	`666`	`+ cast: PointerCoercion::Unsize,`
	`667`	`+ source: eid,`
	`668`	`+ is_from_as_cast: _,`
	`669`	`+ }`
	`670`	`+ \| &ExprKind::Scope { region_scope: _, lint_level: _, value: eid } => {`
	`671`	`+ ek = &self.thir[eid].kind`
	`672`	`+ }`
	`673`	`+ _ => return matches!(Category::of(&ek), Some(Category::Constant)),`
	`674`	`+ }`
	`675`	`+ }`
	`676`	`+ }`
	`677`	`+`
`659`	`678`	`fn build_zero_repeat(`
`660`	`679`	`&mut self,`
`661`	`680`	`mut block: BasicBlock,`
`@@ -666,7 +685,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {`
`666`	`685`	`let this = self;`
`667`	`686`	`let value_expr = &this.thir[value];`
`668`	`687`	`let elem_ty = value_expr.ty;`
`669`		`- if letSome(Category::Constant) = Category::of(&value_expr.kind) {`
	`688`	`+ if this.check_constness(&value_expr.kind) {`
`670`	`689`	`// Repeating a const does nothing`
`671`	`690`	`} else {`
`672`	`691`	// For a non-const, we may need to generate an appropriate `Drop`

`‎tests/ui/coercion/issue-143671.rs`

Lines changed: 30 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,30 @@`
	`1`	`+//@ run-pass`
	`2`	`+`
	`3`	`+#![feature(unsize)]`
	`4`	`+#![feature(coerce_unsized)]`
	`5`	`+`
	`6`	`+use std::fmt::Display;`
	`7`	`+use std::marker::Unsize;`
	`8`	`+use std::ops::CoerceUnsized;`
	`9`	`+`
	`10`	`+#[repr(transparent)]`
	`11`	`+struct X<'a, T: ?Sized> {`
	`12`	`+ f: &'a T,`
	`13`	`+}`
	`14`	`+`
	`15`	`+impl<'a, T: ?Sized> Drop for X<'a, T> {`
	`16`	`+ fn drop(&mut self) {`
	`17`	`+ panic!()`
	`18`	`+ }`
	`19`	`+}`
	`20`	`+`
	`21`	`+impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<X<'a, U>> for X<'a, T> where`
	`22`	`+ &'a T: CoerceUnsized<&'a U>`
	`23`	`+{`
	`24`	`+}`
	`25`	`+`
	`26`	`+const Y: X<'static, i32> = X { f: &0 };`
	`27`	`+`
	`28`	`+fn main() {`
	`29`	`+ let _: [X<'static, dyn Display>; 0] = [Y; 0];`
	`30`	`+}`

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Commit 6a64501

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2 files changed

2 files changed

`‎compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs`

`‎tests/ui/coercion/issue-143671.rs`

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