498 lines
22 KiB
Rust
498 lines
22 KiB
Rust
//! See docs in build/expr/mod.rs
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use crate::build::expr::category::{Category, RvalueFunc};
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use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
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use crate::thir::*;
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use rustc_ast::InlineAsmOptions;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_data_structures::stack::ensure_sufficient_stack;
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use rustc_hir as hir;
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use rustc_index::vec::Idx;
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use rustc_middle::mir::*;
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use rustc_middle::ty::{self, CanonicalUserTypeAnnotation};
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impl<'a, 'tcx> Builder<'a, 'tcx> {
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/// Compile `expr`, storing the result into `destination`, which
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/// is assumed to be uninitialized.
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crate fn expr_into_dest(
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&mut self,
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destination: Place<'tcx>,
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mut block: BasicBlock,
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expr: &Expr<'_, 'tcx>,
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) -> BlockAnd<()> {
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debug!("expr_into_dest(destination={:?}, block={:?}, expr={:?})", destination, block, expr);
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// since we frequently have to reference `self` from within a
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// closure, where `self` would be shadowed, it's easier to
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// just use the name `this` uniformly
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let this = self;
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let expr_span = expr.span;
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let source_info = this.source_info(expr_span);
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let expr_is_block_or_scope =
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matches!(expr.kind, ExprKind::Block { .. } | ExprKind::Scope { .. });
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if !expr_is_block_or_scope {
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this.block_context.push(BlockFrame::SubExpr);
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}
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let block_and = match expr.kind {
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ExprKind::Scope { region_scope, lint_level, value } => {
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let region_scope = (region_scope, source_info);
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ensure_sufficient_stack(|| {
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this.in_scope(region_scope, lint_level, |this| {
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this.expr_into_dest(destination, block, value)
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})
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})
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}
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ExprKind::Block { body: ref ast_block } => {
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this.ast_block(destination, block, ast_block, source_info)
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}
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ExprKind::Match { scrutinee, arms } => {
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this.match_expr(destination, expr_span, block, scrutinee, arms)
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}
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ExprKind::If { cond, then, else_opt } => {
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let place = unpack!(
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block = this.as_temp(block, Some(this.local_scope()), cond, Mutability::Mut)
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);
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let operand = Operand::Move(Place::from(place));
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let mut then_block = this.cfg.start_new_block();
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let mut else_block = this.cfg.start_new_block();
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let term = TerminatorKind::if_(this.tcx, operand, then_block, else_block);
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this.cfg.terminate(block, source_info, term);
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unpack!(then_block = this.expr_into_dest(destination, then_block, then));
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else_block = if let Some(else_opt) = else_opt {
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unpack!(this.expr_into_dest(destination, else_block, else_opt))
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} else {
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// Body of the `if` expression without an `else` clause must return `()`, thus
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// we implicitly generate a `else {}` if it is not specified.
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let correct_si = this.source_info(expr_span.shrink_to_hi());
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this.cfg.push_assign_unit(else_block, correct_si, destination, this.tcx);
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else_block
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};
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let join_block = this.cfg.start_new_block();
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this.cfg.terminate(
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then_block,
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source_info,
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TerminatorKind::Goto { target: join_block },
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);
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this.cfg.terminate(
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else_block,
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source_info,
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TerminatorKind::Goto { target: join_block },
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);
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join_block.unit()
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}
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ExprKind::NeverToAny { source } => {
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let is_call =
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matches!(source.kind, ExprKind::Call { .. } | ExprKind::InlineAsm { .. });
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// (#66975) Source could be a const of type `!`, so has to
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// exist in the generated MIR.
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unpack!(
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block = this.as_temp(block, Some(this.local_scope()), source, Mutability::Mut,)
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);
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// This is an optimization. If the expression was a call then we already have an
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// unreachable block. Don't bother to terminate it and create a new one.
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if is_call {
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block.unit()
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} else {
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this.cfg.terminate(block, source_info, TerminatorKind::Unreachable);
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let end_block = this.cfg.start_new_block();
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end_block.unit()
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}
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}
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ExprKind::LogicalOp { op, lhs, rhs } => {
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// And:
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//
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// [block: If(lhs)] -true-> [else_block: If(rhs)] -true-> [true_block]
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// | | (false)
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// +----------false-----------+------------------> [false_block]
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//
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// Or:
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//
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// [block: If(lhs)] -false-> [else_block: If(rhs)] -true-> [true_block]
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// | (true) | (false)
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// [true_block] [false_block]
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let (true_block, false_block, mut else_block, join_block) = (
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this.cfg.start_new_block(),
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this.cfg.start_new_block(),
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this.cfg.start_new_block(),
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this.cfg.start_new_block(),
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);
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let lhs = unpack!(block = this.as_local_operand(block, lhs));
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let blocks = match op {
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LogicalOp::And => (else_block, false_block),
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LogicalOp::Or => (true_block, else_block),
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};
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let term = TerminatorKind::if_(this.tcx, lhs, blocks.0, blocks.1);
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this.cfg.terminate(block, source_info, term);
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let rhs = unpack!(else_block = this.as_local_operand(else_block, rhs));
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let term = TerminatorKind::if_(this.tcx, rhs, true_block, false_block);
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this.cfg.terminate(else_block, source_info, term);
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this.cfg.push_assign_constant(
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true_block,
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source_info,
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destination,
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Constant {
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span: expr_span,
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user_ty: None,
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literal: ty::Const::from_bool(this.tcx, true).into(),
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},
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);
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this.cfg.push_assign_constant(
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false_block,
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source_info,
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destination,
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Constant {
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span: expr_span,
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user_ty: None,
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literal: ty::Const::from_bool(this.tcx, false).into(),
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},
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);
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// Link up both branches:
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this.cfg.goto(true_block, source_info, join_block);
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this.cfg.goto(false_block, source_info, join_block);
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join_block.unit()
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}
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ExprKind::Loop { body } => {
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// [block]
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// |
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// [loop_block] -> [body_block] -/eval. body/-> [body_block_end]
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// | ^ |
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// false link | |
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// | +-----------------------------------------+
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// +-> [diverge_cleanup]
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// The false link is required to make sure borrowck considers unwinds through the
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// body, even when the exact code in the body cannot unwind
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let loop_block = this.cfg.start_new_block();
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// Start the loop.
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this.cfg.goto(block, source_info, loop_block);
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this.in_breakable_scope(Some(loop_block), destination, expr_span, move |this| {
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// conduct the test, if necessary
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let body_block = this.cfg.start_new_block();
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this.cfg.terminate(
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loop_block,
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source_info,
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TerminatorKind::FalseUnwind { real_target: body_block, unwind: None },
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);
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this.diverge_from(loop_block);
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// The “return” value of the loop body must always be an unit. We therefore
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// introduce a unit temporary as the destination for the loop body.
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let tmp = this.get_unit_temp();
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// Execute the body, branching back to the test.
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let body_block_end = unpack!(this.expr_into_dest(tmp, body_block, body));
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this.cfg.goto(body_block_end, source_info, loop_block);
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// Loops are only exited by `break` expressions.
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None
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})
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}
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ExprKind::Call { ty: _, fun, args, from_hir_call, fn_span } => {
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let fun = unpack!(block = this.as_local_operand(block, fun));
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let args: Vec<_> = args
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.into_iter()
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.map(|arg| unpack!(block = this.as_local_call_operand(block, arg)))
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.collect();
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let success = this.cfg.start_new_block();
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this.record_operands_moved(&args);
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debug!("expr_into_dest: fn_span={:?}", fn_span);
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this.cfg.terminate(
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block,
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source_info,
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TerminatorKind::Call {
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func: fun,
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args,
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cleanup: None,
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// FIXME(varkor): replace this with an uninhabitedness-based check.
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// This requires getting access to the current module to call
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// `tcx.is_ty_uninhabited_from`, which is currently tricky to do.
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destination: if expr.ty.is_never() {
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None
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} else {
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Some((destination, success))
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},
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from_hir_call,
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fn_span,
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},
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);
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this.diverge_from(block);
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success.unit()
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}
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ExprKind::Use { source } => this.expr_into_dest(destination, block, source),
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ExprKind::Borrow { arg, borrow_kind } => {
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// We don't do this in `as_rvalue` because we use `as_place`
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// for borrow expressions, so we cannot create an `RValue` that
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// remains valid across user code. `as_rvalue` is usually called
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// by this method anyway, so this shouldn't cause too many
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// unnecessary temporaries.
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let arg_place = match borrow_kind {
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BorrowKind::Shared => unpack!(block = this.as_read_only_place(block, arg)),
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_ => unpack!(block = this.as_place(block, arg)),
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};
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let borrow = Rvalue::Ref(this.tcx.lifetimes.re_erased, borrow_kind, arg_place);
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this.cfg.push_assign(block, source_info, destination, borrow);
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block.unit()
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}
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ExprKind::AddressOf { mutability, arg } => {
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let place = match mutability {
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hir::Mutability::Not => this.as_read_only_place(block, arg),
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hir::Mutability::Mut => this.as_place(block, arg),
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};
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let address_of = Rvalue::AddressOf(mutability, unpack!(block = place));
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this.cfg.push_assign(block, source_info, destination, address_of);
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block.unit()
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}
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ExprKind::Adt { adt_def, variant_index, substs, user_ty, fields, ref base } => {
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// See the notes for `ExprKind::Array` in `as_rvalue` and for
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// `ExprKind::Borrow` above.
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let is_union = adt_def.is_union();
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let active_field_index = if is_union { Some(fields[0].name.index()) } else { None };
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let scope = this.local_scope();
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// first process the set of fields that were provided
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// (evaluating them in order given by user)
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let fields_map: FxHashMap<_, _> = fields
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.into_iter()
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.map(|f| (f.name, unpack!(block = this.as_operand(block, Some(scope), f.expr))))
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.collect();
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let field_names: Vec<_> =
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(0..adt_def.variants[variant_index].fields.len()).map(Field::new).collect();
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let fields: Vec<_> = if let Some(FruInfo { base, field_types }) = base {
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let place_builder = unpack!(block = this.as_place_builder(block, base));
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// MIR does not natively support FRU, so for each
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// base-supplied field, generate an operand that
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// reads it from the base.
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field_names
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.into_iter()
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.zip(field_types.into_iter())
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.map(|(n, ty)| match fields_map.get(&n) {
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Some(v) => v.clone(),
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None => {
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let place_builder = place_builder.clone();
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this.consume_by_copy_or_move(
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place_builder
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.field(n, ty)
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.into_place(this.tcx, this.typeck_results),
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)
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}
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})
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.collect()
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} else {
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field_names.iter().filter_map(|n| fields_map.get(n).cloned()).collect()
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};
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let inferred_ty = expr.ty;
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let user_ty = user_ty.map(|ty| {
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this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
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span: source_info.span,
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user_ty: ty,
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inferred_ty,
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})
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});
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let adt = box AggregateKind::Adt(
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adt_def,
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variant_index,
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substs,
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user_ty,
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active_field_index,
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);
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this.cfg.push_assign(
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block,
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source_info,
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destination,
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Rvalue::Aggregate(adt, fields),
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);
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block.unit()
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}
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ExprKind::InlineAsm { template, operands, options, line_spans } => {
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use crate::thir;
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use rustc_middle::mir;
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let operands = operands
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.into_iter()
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.map(|op| match *op {
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thir::InlineAsmOperand::In { reg, expr } => mir::InlineAsmOperand::In {
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reg,
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value: unpack!(block = this.as_local_operand(block, expr)),
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},
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thir::InlineAsmOperand::Out { reg, late, expr } => {
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mir::InlineAsmOperand::Out {
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reg,
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late,
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place: expr
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.as_ref()
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.map(|expr| unpack!(block = this.as_place(block, expr))),
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}
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}
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thir::InlineAsmOperand::InOut { reg, late, expr } => {
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let place = unpack!(block = this.as_place(block, expr));
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mir::InlineAsmOperand::InOut {
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reg,
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late,
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// This works because asm operands must be Copy
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in_value: Operand::Copy(place),
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out_place: Some(place),
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}
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}
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thir::InlineAsmOperand::SplitInOut { reg, late, in_expr, out_expr } => {
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mir::InlineAsmOperand::InOut {
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reg,
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late,
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in_value: unpack!(block = this.as_local_operand(block, in_expr)),
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out_place: out_expr.as_ref().map(|out_expr| {
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unpack!(block = this.as_place(block, out_expr))
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}),
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}
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}
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thir::InlineAsmOperand::Const { expr } => mir::InlineAsmOperand::Const {
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value: unpack!(block = this.as_local_operand(block, expr)),
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},
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thir::InlineAsmOperand::SymFn { expr } => {
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mir::InlineAsmOperand::SymFn { value: box this.as_constant(expr) }
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}
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thir::InlineAsmOperand::SymStatic { def_id } => {
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mir::InlineAsmOperand::SymStatic { def_id }
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}
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})
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.collect();
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let destination = this.cfg.start_new_block();
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this.cfg.terminate(
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block,
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source_info,
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TerminatorKind::InlineAsm {
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template,
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operands,
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options,
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line_spans,
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destination: if options.contains(InlineAsmOptions::NORETURN) {
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None
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} else {
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Some(destination)
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},
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},
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);
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destination.unit()
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}
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// These cases don't actually need a destination
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ExprKind::Assign { .. }
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| ExprKind::AssignOp { .. }
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| ExprKind::LlvmInlineAsm { .. } => {
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unpack!(block = this.stmt_expr(block, expr, None));
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this.cfg.push_assign_unit(block, source_info, destination, this.tcx);
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block.unit()
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}
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ExprKind::Continue { .. } | ExprKind::Break { .. } | ExprKind::Return { .. } => {
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unpack!(block = this.stmt_expr(block, expr, None));
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// No assign, as these have type `!`.
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block.unit()
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}
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// Avoid creating a temporary
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ExprKind::VarRef { .. }
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| ExprKind::UpvarRef { .. }
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| ExprKind::PlaceTypeAscription { .. }
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| ExprKind::ValueTypeAscription { .. } => {
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debug_assert!(Category::of(&expr.kind) == Some(Category::Place));
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let place = unpack!(block = this.as_place(block, expr));
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let rvalue = Rvalue::Use(this.consume_by_copy_or_move(place));
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this.cfg.push_assign(block, source_info, destination, rvalue);
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block.unit()
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}
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ExprKind::Index { .. } | ExprKind::Deref { .. } | ExprKind::Field { .. } => {
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debug_assert_eq!(Category::of(&expr.kind), Some(Category::Place));
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// Create a "fake" temporary variable so that we check that the
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// value is Sized. Usually, this is caught in type checking, but
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// in the case of box expr there is no such check.
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if !destination.projection.is_empty() {
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this.local_decls.push(LocalDecl::new(expr.ty, expr.span));
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}
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let place = unpack!(block = this.as_place(block, expr));
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let rvalue = Rvalue::Use(this.consume_by_copy_or_move(place));
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this.cfg.push_assign(block, source_info, destination, rvalue);
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block.unit()
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}
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ExprKind::Yield { value } => {
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let scope = this.local_scope();
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let value = unpack!(block = this.as_operand(block, Some(scope), value));
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let resume = this.cfg.start_new_block();
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this.cfg.terminate(
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block,
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source_info,
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TerminatorKind::Yield { value, resume, resume_arg: destination, drop: None },
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);
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this.generator_drop_cleanup(block);
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resume.unit()
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}
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// these are the cases that are more naturally handled by some other mode
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ExprKind::Unary { .. }
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| ExprKind::Binary { .. }
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| ExprKind::Box { .. }
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| ExprKind::Cast { .. }
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| ExprKind::Pointer { .. }
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| ExprKind::Repeat { .. }
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| ExprKind::Array { .. }
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| ExprKind::Tuple { .. }
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| ExprKind::Closure { .. }
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| ExprKind::ConstBlock { .. }
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| ExprKind::Literal { .. }
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| ExprKind::ThreadLocalRef(_)
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| ExprKind::StaticRef { .. } => {
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debug_assert!(match Category::of(&expr.kind).unwrap() {
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// should be handled above
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Category::Rvalue(RvalueFunc::Into) => false,
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// must be handled above or else we get an
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// infinite loop in the builder; see
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|
// e.g., `ExprKind::VarRef` above
|
|
Category::Place => false,
|
|
|
|
_ => true,
|
|
});
|
|
|
|
let rvalue = unpack!(block = this.as_local_rvalue(block, expr));
|
|
this.cfg.push_assign(block, source_info, destination, rvalue);
|
|
block.unit()
|
|
}
|
|
};
|
|
|
|
if !expr_is_block_or_scope {
|
|
let popped = this.block_context.pop();
|
|
assert!(popped.is_some());
|
|
}
|
|
|
|
block_and
|
|
}
|
|
}
|