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Delegation: support coercion for target expression

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This commit is contained in:
Bryanskiy 2024-06-18 14:04:28 +03:00
parent 5572759b8d
commit 7ee97f93da
13 changed files with 264 additions and 37 deletions
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84
compiler/rustc_ast_lowering/src/delegation.rs
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@ -38,7 +38,7 @@
use crate::{ImplTraitPosition, ResolverAstLoweringExt};
use super::{ImplTraitContext, LoweringContext, ParamMode};
use super::{ImplTraitContext, LoweringContext, ParamMode, ParenthesizedGenericArgs};
use ast::visit::Visitor;
use hir::def::{DefKind, PartialRes, Res};
@ -259,8 +259,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
self_param_id: pat_node_id,
};
self_resolver.visit_block(block);
let block = this.lower_block(block, false);
this.mk_expr(hir::ExprKind::Block(block, None), block.span)
this.lower_target_expr(&block)
} else {
let pat_hir_id = this.lower_node_id(pat_node_id);
this.generate_arg(pat_hir_id, span)
@ -273,26 +272,81 @@ impl<'hir> LoweringContext<'_, 'hir> {
})
}
// Generates fully qualified call for the resulting body.
// FIXME(fn_delegation): Alternatives for target expression lowering:
// https://github.com/rust-lang/rfcs/pull/3530#issuecomment-2197170600.
fn lower_target_expr(&mut self, block: &Block) -> hir::Expr<'hir> {
if block.stmts.len() == 1
&& let StmtKind::Expr(expr) = &block.stmts[0].kind
{
return self.lower_expr_mut(expr);
}
let block = self.lower_block(block, false);
self.mk_expr(hir::ExprKind::Block(block, None), block.span)
}
// Generates expression for the resulting body. If possible, `MethodCall` is used
// to allow autoref/autoderef for target expression. For example in:
//
// trait Trait : Sized {
// fn by_value(self) -> i32 { 1 }
// fn by_mut_ref(&mut self) -> i32 { 2 }
// fn by_ref(&self) -> i32 { 3 }
// }
//
// struct NewType(SomeType);
// impl Trait for NewType {
// reuse Trait::* { self.0 }
// }
//
// `self.0` will automatically coerce.
fn finalize_body_lowering(
&mut self,
delegation: &Delegation,
args: Vec<hir::Expr<'hir>>,
span: Span,
) -> hir::Expr<'hir> {
let path = self.lower_qpath(
delegation.id,
&delegation.qself,
&delegation.path,
ParamMode::Optional,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
);
let args = self.arena.alloc_from_iter(args);
let path_expr = self.arena.alloc(self.mk_expr(hir::ExprKind::Path(path), span));
let call = self.arena.alloc(self.mk_expr(hir::ExprKind::Call(path_expr, args), span));
let has_generic_args =
delegation.path.segments.iter().rev().skip(1).any(|segment| segment.args.is_some());
let call = if self
.get_resolution_id(delegation.id, span)
.and_then(|def_id| Ok(self.has_self(def_id, span)))
.unwrap_or_default()
&& delegation.qself.is_none()
&& !has_generic_args
{
let ast_segment = delegation.path.segments.last().unwrap();
let segment = self.lower_path_segment(
delegation.path.span,
ast_segment,
ParamMode::Optional,
ParenthesizedGenericArgs::Err,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
);
let segment = self.arena.alloc(segment);
self.arena.alloc(hir::Expr {
hir_id: self.next_id(),
kind: hir::ExprKind::MethodCall(segment, &args[0], &args[1..], span),
span,
})
} else {
let path = self.lower_qpath(
delegation.id,
&delegation.qself,
&delegation.path,
ParamMode::Optional,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
);
let callee_path = self.arena.alloc(self.mk_expr(hir::ExprKind::Path(path), span));
self.arena.alloc(self.mk_expr(hir::ExprKind::Call(callee_path, args), span))
};
let block = self.arena.alloc(hir::Block {
stmts: &[],
expr: Some(call),