Auto merge of #32232 - jonas-schievink:issue31511, r=eddyb
Give a more accurate error on thin-to-fat ptr cast Fixes #31511
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af8f85cc39
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@ -100,6 +100,8 @@ enum CastError {
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CastToBool,
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CastToChar,
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DifferingKinds,
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/// Cast of thin to fat raw ptr (eg. `*const () as *const [u8]`)
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SizedUnsizedCast,
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IllegalCast,
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NeedViaPtr,
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NeedViaThinPtr,
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@ -165,6 +167,13 @@ impl<'tcx> CastCheck<'tcx> {
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fcx.infcx().ty_to_string(self.cast_ty))
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}, self.expr_ty, None);
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}
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CastError::SizedUnsizedCast => {
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fcx.type_error_message(self.span, |actual| {
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format!("cannot cast thin pointer `{}` to fat pointer `{}`",
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actual,
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fcx.infcx().ty_to_string(self.cast_ty))
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}, self.expr_ty, None)
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}
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CastError::DifferingKinds => {
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fcx.type_error_struct(self.span, |actual| {
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format!("casting `{}` as `{}` is invalid",
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@ -312,7 +321,7 @@ impl<'tcx> CastCheck<'tcx> {
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// sized -> unsized? report invalid cast (don't complain about vtable kinds)
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if fcx.type_is_known_to_be_sized(m_expr.ty, self.span) {
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return Err(CastError::IllegalCast);
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return Err(CastError::SizedUnsizedCast);
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}
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// vtable kinds must match
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@ -87,7 +87,7 @@ fn main()
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//~^^ HELP through a usize first
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let _ = 42usize as *const [u8]; //~ ERROR casting
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let _ = v as *const [u8]; //~ ERROR casting
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let _ = v as *const [u8]; //~ ERROR cannot cast
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let _ = fat_v as *const Foo;
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//~^ ERROR `core::marker::Sized` is not implemented for the type `[u8]`
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let _ = foo as *const str; //~ ERROR casting
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@ -24,7 +24,7 @@ fn main() {
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//~^^ HELP cast through a thin pointer
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// #22955
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q as *const [i32]; //~ ERROR casting
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q as *const [i32]; //~ ERROR cannot cast
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// #21397
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let t: *mut (Trait + 'static) = 0 as *mut _; //~ ERROR casting
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@ -0,0 +1,16 @@
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// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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fn cast_thin_to_fat(x: *const ()) {
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x as *const [u8];
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//~^ ERROR: cannot cast thin pointer `*const ()` to fat pointer `*const [u8]`
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}
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fn main() {}
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