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Rollup merge of rust-lang#60417 - Centril:hir-exprkind-use-renamed-to…
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…-drop-temps, r=oli-obk

Rename hir::ExprKind::Use to ::DropTemps and improve docs.

Addresses rust-lang#60225 (comment).

r? @oli-obk

cc @eddyb @Manishearth
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Centril authored Apr 30, 2019
2 parents 4a2604d + d58cb93 commit 92e69cd
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Showing 12 changed files with 32 additions and 26 deletions.
2 changes: 1 addition & 1 deletion src/librustc/cfg/construct.rs
Original file line number Diff line number Diff line change
Expand Up @@ -369,7 +369,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
hir::ExprKind::AddrOf(_, ref e) |
hir::ExprKind::Cast(ref e, _) |
hir::ExprKind::Type(ref e, _) |
hir::ExprKind::Use(ref e) |
hir::ExprKind::DropTemps(ref e) |
hir::ExprKind::Unary(_, ref e) |
hir::ExprKind::Field(ref e, _) |
hir::ExprKind::Yield(ref e) |
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2 changes: 1 addition & 1 deletion src/librustc/hir/intravisit.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1029,7 +1029,7 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
visitor.visit_expr(subexpression);
visitor.visit_ty(typ)
}
ExprKind::Use(ref subexpression) => {
ExprKind::DropTemps(ref subexpression) => {
visitor.visit_expr(subexpression);
}
ExprKind::If(ref head_expression, ref if_block, ref optional_else) => {
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18 changes: 11 additions & 7 deletions src/librustc/hir/lowering.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4671,7 +4671,7 @@ impl<'a> LoweringContext<'a> {
// The construct was introduced in #21984.
// FIXME(60253): Is this still necessary?
// Also, add the attributes to the outer returned expr node.
return self.expr_use(head_sp, match_expr, e.attrs.clone())
return self.expr_drop_temps(head_sp, match_expr, e.attrs.clone())
}

// Desugar `ExprKind::Try`
Expand Down Expand Up @@ -5030,15 +5030,19 @@ impl<'a> LoweringContext<'a> {
)
}

/// Wrap the given `expr` in `hir::ExprKind::Use`.
/// Wrap the given `expr` in a terminating scope using `hir::ExprKind::DropTemps`.
///
/// In terms of drop order, it has the same effect as
/// wrapping `expr` in `{ let _t = $expr; _t }` but
/// should provide better compile-time performance.
/// In terms of drop order, it has the same effect as wrapping `expr` in
/// `{ let _t = $expr; _t }` but should provide better compile-time performance.
///
/// The drop order can be important in e.g. `if expr { .. }`.
fn expr_use(&mut self, span: Span, expr: P<hir::Expr>, attrs: ThinVec<Attribute>) -> hir::Expr {
self.expr(span, hir::ExprKind::Use(expr), attrs)
fn expr_drop_temps(
&mut self,
span: Span,
expr: P<hir::Expr>,
attrs: ThinVec<Attribute>
) -> hir::Expr {
self.expr(span, hir::ExprKind::DropTemps(expr), attrs)
}

fn expr_match(
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14 changes: 8 additions & 6 deletions src/librustc/hir/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1366,7 +1366,7 @@ impl Expr {
ExprKind::Unary(..) => ExprPrecedence::Unary,
ExprKind::Lit(_) => ExprPrecedence::Lit,
ExprKind::Type(..) | ExprKind::Cast(..) => ExprPrecedence::Cast,
ExprKind::Use(ref expr, ..) => expr.precedence(),
ExprKind::DropTemps(ref expr, ..) => expr.precedence(),
ExprKind::If(..) => ExprPrecedence::If,
ExprKind::While(..) => ExprPrecedence::While,
ExprKind::Loop(..) => ExprPrecedence::Loop,
Expand Down Expand Up @@ -1438,7 +1438,7 @@ impl Expr {
ExprKind::Binary(..) |
ExprKind::Yield(..) |
ExprKind::Cast(..) |
ExprKind::Use(..) |
ExprKind::DropTemps(..) |
ExprKind::Err => {
false
}
Expand Down Expand Up @@ -1488,10 +1488,12 @@ pub enum ExprKind {
Cast(P<Expr>, P<Ty>),
/// A type reference (e.g., `Foo`).
Type(P<Expr>, P<Ty>),
/// Semantically equivalent to `{ let _t = expr; _t }`.
/// Maps directly to `hair::ExprKind::Use`.
/// Only exists to tweak the drop order in HIR.
Use(P<Expr>),
/// Wraps the expression in a terminating scope.
/// This makes it semantically equivalent to `{ let _t = expr; _t }`.
///
/// This construct only exists to tweak the drop order in HIR lowering.
/// An example of that is the desugaring of `for` loops.
DropTemps(P<Expr>),
/// An `if` block, with an optional else block.
///
/// I.e., `if <expr> { <expr> } else { <expr> }`.
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2 changes: 1 addition & 1 deletion src/librustc/hir/print.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1388,7 +1388,7 @@ impl<'a> State<'a> {
self.word_space(":")?;
self.print_type(&ty)?;
}
hir::ExprKind::Use(ref init) => {
hir::ExprKind::DropTemps(ref init) => {
// Print `{`:
self.cbox(indent_unit)?;
self.ibox(0)?;
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2 changes: 1 addition & 1 deletion src/librustc/middle/expr_use_visitor.rs
Original file line number Diff line number Diff line change
Expand Up @@ -520,7 +520,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
self.consume_expr(&base);
}

hir::ExprKind::Use(ref expr) => {
hir::ExprKind::DropTemps(ref expr) => {
self.consume_expr(&expr);
}

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6 changes: 3 additions & 3 deletions src/librustc/middle/liveness.rs
Original file line number Diff line number Diff line change
Expand Up @@ -521,7 +521,7 @@ fn visit_expr<'a, 'tcx>(ir: &mut IrMaps<'a, 'tcx>, expr: &'tcx Expr) {
hir::ExprKind::Binary(..) |
hir::ExprKind::AddrOf(..) |
hir::ExprKind::Cast(..) |
hir::ExprKind::Use(..) |
hir::ExprKind::DropTemps(..) |
hir::ExprKind::Unary(..) |
hir::ExprKind::Break(..) |
hir::ExprKind::Continue(_) |
Expand Down Expand Up @@ -1222,7 +1222,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
hir::ExprKind::AddrOf(_, ref e) |
hir::ExprKind::Cast(ref e, _) |
hir::ExprKind::Type(ref e, _) |
hir::ExprKind::Use(ref e) |
hir::ExprKind::DropTemps(ref e) |
hir::ExprKind::Unary(_, ref e) |
hir::ExprKind::Yield(ref e) |
hir::ExprKind::Repeat(ref e, _) => {
Expand Down Expand Up @@ -1526,7 +1526,7 @@ fn check_expr<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, expr: &'tcx Expr) {
hir::ExprKind::Match(..) | hir::ExprKind::While(..) | hir::ExprKind::Loop(..) |
hir::ExprKind::Index(..) | hir::ExprKind::Field(..) |
hir::ExprKind::Array(..) | hir::ExprKind::Tup(..) | hir::ExprKind::Binary(..) |
hir::ExprKind::Cast(..) | hir::ExprKind::Use(..) | hir::ExprKind::Unary(..) |
hir::ExprKind::Cast(..) | hir::ExprKind::DropTemps(..) | hir::ExprKind::Unary(..) |
hir::ExprKind::Ret(..) | hir::ExprKind::Break(..) | hir::ExprKind::Continue(..) |
hir::ExprKind::Lit(_) | hir::ExprKind::Block(..) | hir::ExprKind::AddrOf(..) |
hir::ExprKind::Struct(..) | hir::ExprKind::Repeat(..) |
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2 changes: 1 addition & 1 deletion src/librustc/middle/mem_categorization.rs
Original file line number Diff line number Diff line change
Expand Up @@ -677,7 +677,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
hir::ExprKind::Assign(..) | hir::ExprKind::AssignOp(..) |
hir::ExprKind::Closure(..) | hir::ExprKind::Ret(..) |
hir::ExprKind::Unary(..) | hir::ExprKind::Yield(..) |
hir::ExprKind::MethodCall(..) | hir::ExprKind::Cast(..) | hir::ExprKind::Use(..) |
hir::ExprKind::MethodCall(..) | hir::ExprKind::Cast(..) | hir::ExprKind::DropTemps(..) |
hir::ExprKind::Array(..) | hir::ExprKind::Tup(..) | hir::ExprKind::If(..) |
hir::ExprKind::Binary(..) | hir::ExprKind::While(..) |
hir::ExprKind::Block(..) | hir::ExprKind::Loop(..) | hir::ExprKind::Match(..) |
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4 changes: 2 additions & 2 deletions src/librustc/middle/region.rs
Original file line number Diff line number Diff line change
Expand Up @@ -908,8 +908,8 @@ fn resolve_expr<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, expr:
visitor.cx.var_parent = visitor.cx.parent;
}

hir::ExprKind::Use(ref expr) => {
// `Use(expr)` does not denote a conditional scope.
hir::ExprKind::DropTemps(ref expr) => {
// `DropTemps(expr)` does not denote a conditional scope.
// Rather, we want to achieve the same behavior as `{ let _t = expr; _t }`.
terminating(expr.hir_id.local_id);
}
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2 changes: 1 addition & 1 deletion src/librustc_mir/hair/cx/expr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -759,7 +759,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
}
}
}
hir::ExprKind::Use(ref source) => {
hir::ExprKind::DropTemps(ref source) => {
ExprKind::Use { source: source.to_ref() }
}
hir::ExprKind::Box(ref value) => {
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2 changes: 1 addition & 1 deletion src/librustc_passes/rvalue_promotion.rs
Original file line number Diff line number Diff line change
Expand Up @@ -437,7 +437,7 @@ fn check_expr_kind<'a, 'tcx>(
hir::ExprKind::AddrOf(_, ref expr) |
hir::ExprKind::Repeat(ref expr, _) |
hir::ExprKind::Type(ref expr, _) |
hir::ExprKind::Use(ref expr) => {
hir::ExprKind::DropTemps(ref expr) => {
v.check_expr(&expr)
}

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2 changes: 1 addition & 1 deletion src/librustc_typeck/check/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4538,7 +4538,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
self.check_expr_eq_type(&e, ty);
ty
}
ExprKind::Use(ref e) => {
ExprKind::DropTemps(ref e) => {
self.check_expr_with_expectation(e, expected)
}
ExprKind::Array(ref args) => {
Expand Down

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