666 lines
23 KiB
Rust
666 lines
23 KiB
Rust
//! A different sort of visitor for walking fn bodies. Unlike the
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//! normal visitor, which just walks the entire body in one shot, the
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//! `ExprUseVisitor` determines how expressions are being used.
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pub use self::ConsumeMode::*;
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use self::OverloadedCallType::*;
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use crate::hir::def::Res;
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use crate::hir::def_id::DefId;
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use crate::hir::ptr::P;
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use crate::infer::InferCtxt;
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use crate::middle::mem_categorization as mc;
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use crate::middle::region;
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use crate::ty::{self, TyCtxt, adjustment};
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use crate::hir::{self, PatKind};
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use std::rc::Rc;
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use syntax_pos::Span;
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///////////////////////////////////////////////////////////////////////////
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// The Delegate trait
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/// This trait defines the callbacks you can expect to receive when
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/// employing the ExprUseVisitor.
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pub trait Delegate<'tcx> {
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// The value found at `cmt` is either copied or moved, depending
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// on mode.
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fn consume(&mut self, cmt: &mc::cmt_<'tcx>, mode: ConsumeMode);
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// The value found at `cmt` is being borrowed with kind `bk`.
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fn borrow(&mut self, cmt: &mc::cmt_<'tcx>, bk: ty::BorrowKind);
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// The path at `cmt` is being assigned to.
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fn mutate(&mut self, assignee_cmt: &mc::cmt_<'tcx>);
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}
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#[derive(Copy, Clone, PartialEq, Debug)]
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pub enum ConsumeMode {
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Copy, // reference to x where x has a type that copies
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Move, // reference to x where x has a type that moves
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}
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#[derive(Copy, Clone, PartialEq, Debug)]
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pub enum MutateMode {
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Init,
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JustWrite, // x = y
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WriteAndRead, // x += y
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}
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#[derive(Copy, Clone)]
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enum OverloadedCallType {
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FnOverloadedCall,
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FnMutOverloadedCall,
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FnOnceOverloadedCall,
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}
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impl OverloadedCallType {
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fn from_trait_id(tcx: TyCtxt<'_>, trait_id: DefId) -> OverloadedCallType {
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for &(maybe_function_trait, overloaded_call_type) in &[
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(tcx.lang_items().fn_once_trait(), FnOnceOverloadedCall),
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(tcx.lang_items().fn_mut_trait(), FnMutOverloadedCall),
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(tcx.lang_items().fn_trait(), FnOverloadedCall)
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] {
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match maybe_function_trait {
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Some(function_trait) if function_trait == trait_id => {
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return overloaded_call_type
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}
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_ => continue,
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}
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}
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bug!("overloaded call didn't map to known function trait")
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}
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fn from_method_id(tcx: TyCtxt<'_>, method_id: DefId) -> OverloadedCallType {
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let method = tcx.associated_item(method_id);
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OverloadedCallType::from_trait_id(tcx, method.container.id())
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}
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}
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///////////////////////////////////////////////////////////////////////////
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// The ExprUseVisitor type
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//
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// This is the code that actually walks the tree.
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pub struct ExprUseVisitor<'a, 'tcx> {
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mc: mc::MemCategorizationContext<'a, 'tcx>,
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delegate: &'a mut dyn Delegate<'tcx>,
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param_env: ty::ParamEnv<'tcx>,
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}
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// If the MC results in an error, it's because the type check
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// failed (or will fail, when the error is uncovered and reported
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// during writeback). In this case, we just ignore this part of the
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// code.
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//
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// Note that this macro appears similar to try!(), but, unlike try!(),
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// it does not propagate the error.
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macro_rules! return_if_err {
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($inp: expr) => (
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match $inp {
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Ok(v) => v,
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Err(()) => {
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debug!("mc reported err");
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return
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}
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}
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)
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}
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impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
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/// Creates the ExprUseVisitor, configuring it with the various options provided:
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///
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/// - `delegate` -- who receives the callbacks
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/// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`)
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/// - `region_scope_tree` --- region scope tree for the code being analyzed
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/// - `tables` --- typeck results for the code being analyzed
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///
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/// See also `with_infer`, which is used *during* typeck.
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pub fn new(
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delegate: &'a mut (dyn Delegate<'tcx> + 'a),
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tcx: TyCtxt<'tcx>,
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body_owner: DefId,
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param_env: ty::ParamEnv<'tcx>,
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region_scope_tree: &'a region::ScopeTree,
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tables: &'a ty::TypeckTables<'tcx>,
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) -> Self {
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ExprUseVisitor {
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mc: mc::MemCategorizationContext::new(tcx,
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param_env,
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body_owner,
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region_scope_tree,
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tables),
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delegate,
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param_env,
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}
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}
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}
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impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
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pub fn with_infer(
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delegate: &'a mut (dyn Delegate<'tcx> + 'a),
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infcx: &'a InferCtxt<'a, 'tcx>,
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body_owner: DefId,
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param_env: ty::ParamEnv<'tcx>,
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region_scope_tree: &'a region::ScopeTree,
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tables: &'a ty::TypeckTables<'tcx>,
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) -> Self {
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ExprUseVisitor {
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mc: mc::MemCategorizationContext::with_infer(
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infcx,
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param_env,
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body_owner,
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region_scope_tree,
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tables,
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),
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delegate,
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param_env,
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}
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}
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pub fn consume_body(&mut self, body: &hir::Body) {
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debug!("consume_body(body={:?})", body);
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for param in &body.params {
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let param_ty = return_if_err!(self.mc.pat_ty_adjusted(¶m.pat));
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debug!("consume_body: param_ty = {:?}", param_ty);
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let param_cmt = Rc::new(self.mc.cat_rvalue(
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param.hir_id,
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param.pat.span,
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param_ty));
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self.walk_irrefutable_pat(param_cmt, ¶m.pat);
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}
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self.consume_expr(&body.value);
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}
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fn tcx(&self) -> TyCtxt<'tcx> {
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self.mc.tcx
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}
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fn delegate_consume(&mut self, cmt: &mc::cmt_<'tcx>) {
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debug!("delegate_consume(cmt={:?})", cmt);
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let mode = copy_or_move(&self.mc, self.param_env, cmt);
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self.delegate.consume(cmt, mode);
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}
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fn consume_exprs(&mut self, exprs: &[hir::Expr]) {
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for expr in exprs {
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self.consume_expr(&expr);
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}
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}
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pub fn consume_expr(&mut self, expr: &hir::Expr) {
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debug!("consume_expr(expr={:?})", expr);
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let cmt = return_if_err!(self.mc.cat_expr(expr));
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self.delegate_consume(&cmt);
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self.walk_expr(expr);
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}
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fn mutate_expr(&mut self, expr: &hir::Expr) {
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let cmt = return_if_err!(self.mc.cat_expr(expr));
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self.delegate.mutate(&cmt);
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self.walk_expr(expr);
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}
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fn borrow_expr(&mut self, expr: &hir::Expr, bk: ty::BorrowKind) {
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debug!("borrow_expr(expr={:?}, bk={:?})", expr, bk);
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let cmt = return_if_err!(self.mc.cat_expr(expr));
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self.delegate.borrow(&cmt, bk);
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self.walk_expr(expr)
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}
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fn select_from_expr(&mut self, expr: &hir::Expr) {
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self.walk_expr(expr)
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}
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pub fn walk_expr(&mut self, expr: &hir::Expr) {
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debug!("walk_expr(expr={:?})", expr);
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self.walk_adjustment(expr);
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match expr.kind {
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hir::ExprKind::Path(_) => { }
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hir::ExprKind::Type(ref subexpr, _) => {
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self.walk_expr(subexpr)
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}
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hir::ExprKind::Unary(hir::UnDeref, ref base) => { // *base
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self.select_from_expr(base);
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}
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hir::ExprKind::Field(ref base, _) => { // base.f
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self.select_from_expr(base);
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}
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hir::ExprKind::Index(ref lhs, ref rhs) => { // lhs[rhs]
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self.select_from_expr(lhs);
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self.consume_expr(rhs);
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}
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hir::ExprKind::Call(ref callee, ref args) => { // callee(args)
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self.walk_callee(expr, callee);
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self.consume_exprs(args);
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}
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hir::ExprKind::MethodCall(.., ref args) => { // callee.m(args)
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self.consume_exprs(args);
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}
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hir::ExprKind::Struct(_, ref fields, ref opt_with) => {
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self.walk_struct_expr(fields, opt_with);
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}
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hir::ExprKind::Tup(ref exprs) => {
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self.consume_exprs(exprs);
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}
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hir::ExprKind::Match(ref discr, ref arms, _) => {
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let discr_cmt = Rc::new(return_if_err!(self.mc.cat_expr(&discr)));
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self.borrow_expr(&discr, ty::ImmBorrow);
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// treatment of the discriminant is handled while walking the arms.
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for arm in arms {
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self.walk_arm(discr_cmt.clone(), arm);
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}
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}
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hir::ExprKind::Array(ref exprs) => {
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self.consume_exprs(exprs);
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}
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hir::ExprKind::AddrOf(m, ref base) => { // &base
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// make sure that the thing we are pointing out stays valid
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// for the lifetime `scope_r` of the resulting ptr:
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let bk = ty::BorrowKind::from_mutbl(m);
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self.borrow_expr(&base, bk);
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}
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hir::ExprKind::InlineAsm(ref ia, ref outputs, ref inputs) => {
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for (o, output) in ia.outputs.iter().zip(outputs) {
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if o.is_indirect {
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self.consume_expr(output);
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} else {
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self.mutate_expr(output);
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}
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}
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self.consume_exprs(inputs);
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}
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hir::ExprKind::Continue(..) |
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hir::ExprKind::Lit(..) |
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hir::ExprKind::Err => {}
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hir::ExprKind::Loop(ref blk, _, _) => {
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self.walk_block(blk);
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}
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hir::ExprKind::Unary(_, ref lhs) => {
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self.consume_expr(lhs);
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}
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hir::ExprKind::Binary(_, ref lhs, ref rhs) => {
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self.consume_expr(lhs);
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self.consume_expr(rhs);
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}
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hir::ExprKind::Block(ref blk, _) => {
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self.walk_block(blk);
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}
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hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
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if let Some(ref expr) = *opt_expr {
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self.consume_expr(expr);
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}
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}
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hir::ExprKind::Assign(ref lhs, ref rhs) => {
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self.mutate_expr(lhs);
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self.consume_expr(rhs);
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}
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hir::ExprKind::Cast(ref base, _) => {
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self.consume_expr(base);
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}
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hir::ExprKind::DropTemps(ref expr) => {
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self.consume_expr(expr);
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}
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hir::ExprKind::AssignOp(_, ref lhs, ref rhs) => {
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if self.mc.tables.is_method_call(expr) {
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self.consume_expr(lhs);
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} else {
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self.mutate_expr(lhs);
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}
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self.consume_expr(rhs);
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}
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hir::ExprKind::Repeat(ref base, _) => {
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self.consume_expr(base);
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}
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hir::ExprKind::Closure(_, _, _, fn_decl_span, _) => {
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self.walk_captures(expr, fn_decl_span);
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}
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hir::ExprKind::Box(ref base) => {
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self.consume_expr(base);
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}
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hir::ExprKind::Yield(ref value, _) => {
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self.consume_expr(value);
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}
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}
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}
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fn walk_callee(&mut self, call: &hir::Expr, callee: &hir::Expr) {
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let callee_ty = return_if_err!(self.mc.expr_ty_adjusted(callee));
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debug!("walk_callee: callee={:?} callee_ty={:?}",
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callee, callee_ty);
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match callee_ty.kind {
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ty::FnDef(..) | ty::FnPtr(_) => {
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self.consume_expr(callee);
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}
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ty::Error => { }
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_ => {
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if let Some(def_id) = self.mc.tables.type_dependent_def_id(call.hir_id) {
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match OverloadedCallType::from_method_id(self.tcx(), def_id) {
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FnMutOverloadedCall => {
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self.borrow_expr(callee, ty::MutBorrow);
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}
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FnOverloadedCall => {
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self.borrow_expr(callee, ty::ImmBorrow);
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}
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FnOnceOverloadedCall => self.consume_expr(callee),
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}
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} else {
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self.tcx().sess.delay_span_bug(call.span,
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"no type-dependent def for overloaded call");
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}
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}
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}
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}
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fn walk_stmt(&mut self, stmt: &hir::Stmt) {
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match stmt.kind {
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hir::StmtKind::Local(ref local) => {
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self.walk_local(&local);
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}
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hir::StmtKind::Item(_) => {
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// We don't visit nested items in this visitor,
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// only the fn body we were given.
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}
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hir::StmtKind::Expr(ref expr) |
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hir::StmtKind::Semi(ref expr) => {
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self.consume_expr(&expr);
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}
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}
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}
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fn walk_local(&mut self, local: &hir::Local) {
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if let Some(ref expr) = local.init {
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// Variable declarations with
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// initializers are considered
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// "assigns", which is handled by
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// `walk_pat`:
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self.walk_expr(&expr);
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let init_cmt = Rc::new(return_if_err!(self.mc.cat_expr(&expr)));
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self.walk_irrefutable_pat(init_cmt, &local.pat);
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}
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}
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/// Indicates that the value of `blk` will be consumed, meaning either copied or moved
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/// depending on its type.
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fn walk_block(&mut self, blk: &hir::Block) {
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debug!("walk_block(blk.hir_id={})", blk.hir_id);
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for stmt in &blk.stmts {
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self.walk_stmt(stmt);
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}
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if let Some(ref tail_expr) = blk.expr {
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self.consume_expr(&tail_expr);
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}
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}
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fn walk_struct_expr(&mut self,
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fields: &[hir::Field],
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opt_with: &Option<P<hir::Expr>>) {
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// Consume the expressions supplying values for each field.
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for field in fields {
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self.consume_expr(&field.expr);
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}
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let with_expr = match *opt_with {
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Some(ref w) => &**w,
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None => { return; }
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};
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let with_cmt = Rc::new(return_if_err!(self.mc.cat_expr(&with_expr)));
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// Select just those fields of the `with`
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// expression that will actually be used
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match with_cmt.ty.kind {
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ty::Adt(adt, substs) if adt.is_struct() => {
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// Consume those fields of the with expression that are needed.
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for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
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let is_mentioned = fields.iter().any(|f| {
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self.tcx().field_index(f.hir_id, self.mc.tables) == f_index
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});
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if !is_mentioned {
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let cmt_field = self.mc.cat_field(
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&*with_expr,
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with_cmt.clone(),
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f_index,
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with_field.ident,
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with_field.ty(self.tcx(), substs)
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);
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self.delegate_consume(&cmt_field);
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}
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}
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}
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_ => {
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// the base expression should always evaluate to a
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// struct; however, when EUV is run during typeck, it
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// may not. This will generate an error earlier in typeck,
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// so we can just ignore it.
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if !self.tcx().sess.has_errors() {
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span_bug!(
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with_expr.span,
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"with expression doesn't evaluate to a struct");
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}
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}
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}
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// walk the with expression so that complex expressions
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// are properly handled.
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self.walk_expr(with_expr);
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}
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// Invoke the appropriate delegate calls for anything that gets
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// consumed or borrowed as part of the automatic adjustment
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// process.
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fn walk_adjustment(&mut self, expr: &hir::Expr) {
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let adjustments = self.mc.tables.expr_adjustments(expr);
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let mut cmt = return_if_err!(self.mc.cat_expr_unadjusted(expr));
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for adjustment in adjustments {
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debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
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match adjustment.kind {
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adjustment::Adjust::NeverToAny |
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adjustment::Adjust::Pointer(_) => {
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// Creating a closure/fn-pointer or unsizing consumes
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// the input and stores it into the resulting rvalue.
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self.delegate_consume(&cmt);
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}
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adjustment::Adjust::Deref(None) => {}
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|
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// Autoderefs for overloaded Deref calls in fact reference
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// their receiver. That is, if we have `(*x)` where `x`
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|
// is of type `Rc<T>`, then this in fact is equivalent to
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// `x.deref()`. Since `deref()` is declared with `&self`,
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|
// this is an autoref of `x`.
|
|
adjustment::Adjust::Deref(Some(ref deref)) => {
|
|
let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
|
|
self.delegate.borrow(&cmt, bk);
|
|
}
|
|
|
|
adjustment::Adjust::Borrow(ref autoref) => {
|
|
self.walk_autoref(expr, &cmt, autoref);
|
|
}
|
|
}
|
|
cmt = return_if_err!(self.mc.cat_expr_adjusted(expr, cmt, &adjustment));
|
|
}
|
|
}
|
|
|
|
/// Walks the autoref `autoref` applied to the autoderef'd
|
|
/// `expr`. `cmt_base` is the mem-categorized form of `expr`
|
|
/// after all relevant autoderefs have occurred.
|
|
fn walk_autoref(&mut self,
|
|
expr: &hir::Expr,
|
|
cmt_base: &mc::cmt_<'tcx>,
|
|
autoref: &adjustment::AutoBorrow<'tcx>) {
|
|
debug!("walk_autoref(expr.hir_id={} cmt_base={:?} autoref={:?})",
|
|
expr.hir_id,
|
|
cmt_base,
|
|
autoref);
|
|
|
|
match *autoref {
|
|
adjustment::AutoBorrow::Ref(_, m) => {
|
|
self.delegate.borrow(cmt_base, ty::BorrowKind::from_mutbl(m.into()));
|
|
}
|
|
|
|
adjustment::AutoBorrow::RawPtr(m) => {
|
|
debug!("walk_autoref: expr.hir_id={} cmt_base={:?}",
|
|
expr.hir_id,
|
|
cmt_base);
|
|
|
|
|
|
self.delegate.borrow(cmt_base, ty::BorrowKind::from_mutbl(m));
|
|
}
|
|
}
|
|
}
|
|
|
|
fn walk_arm(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm) {
|
|
self.walk_pat(discr_cmt.clone(), &arm.pat);
|
|
|
|
if let Some(hir::Guard::If(ref e)) = arm.guard {
|
|
self.consume_expr(e)
|
|
}
|
|
|
|
self.consume_expr(&arm.body);
|
|
}
|
|
|
|
/// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
|
|
/// let binding, and *not* a match arm or nested pat.)
|
|
fn walk_irrefutable_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat) {
|
|
self.walk_pat(cmt_discr, pat);
|
|
}
|
|
|
|
|
|
/// The core driver for walking a pattern
|
|
fn walk_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat) {
|
|
debug!("walk_pat(cmt_discr={:?}, pat={:?})", cmt_discr, pat);
|
|
|
|
let tcx = self.tcx();
|
|
let ExprUseVisitor { ref mc, ref mut delegate, param_env } = *self;
|
|
return_if_err!(mc.cat_pattern(cmt_discr.clone(), pat, |cmt_pat, pat| {
|
|
if let PatKind::Binding(_, canonical_id, ..) = pat.kind {
|
|
debug!(
|
|
"walk_pat: binding cmt_pat={:?} pat={:?}",
|
|
cmt_pat,
|
|
pat,
|
|
);
|
|
if let Some(&bm) = mc.tables.pat_binding_modes().get(pat.hir_id) {
|
|
debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
|
|
|
|
// pat_ty: the type of the binding being produced.
|
|
let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
|
|
debug!("walk_pat: pat_ty={:?}", pat_ty);
|
|
|
|
// Each match binding is effectively an assignment to the
|
|
// binding being produced.
|
|
let def = Res::Local(canonical_id);
|
|
if let Ok(ref binding_cmt) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
|
|
delegate.mutate(binding_cmt);
|
|
}
|
|
|
|
// It is also a borrow or copy/move of the value being matched.
|
|
match bm {
|
|
ty::BindByReference(m) => {
|
|
let bk = ty::BorrowKind::from_mutbl(m);
|
|
delegate.borrow(&cmt_pat, bk);
|
|
}
|
|
ty::BindByValue(..) => {
|
|
let mode = copy_or_move(mc, param_env, &cmt_pat);
|
|
debug!("walk_pat binding consuming pat");
|
|
delegate.consume(&cmt_pat, mode);
|
|
}
|
|
}
|
|
} else {
|
|
tcx.sess.delay_span_bug(pat.span, "missing binding mode");
|
|
}
|
|
}
|
|
}));
|
|
}
|
|
|
|
fn walk_captures(&mut self, closure_expr: &hir::Expr, fn_decl_span: Span) {
|
|
debug!("walk_captures({:?})", closure_expr);
|
|
|
|
let closure_def_id = self.tcx().hir().local_def_id(closure_expr.hir_id);
|
|
if let Some(upvars) = self.tcx().upvars(closure_def_id) {
|
|
for &var_id in upvars.keys() {
|
|
let upvar_id = ty::UpvarId {
|
|
var_path: ty::UpvarPath { hir_id: var_id },
|
|
closure_expr_id: closure_def_id.to_local(),
|
|
};
|
|
let upvar_capture = self.mc.tables.upvar_capture(upvar_id);
|
|
let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.hir_id,
|
|
fn_decl_span,
|
|
var_id));
|
|
match upvar_capture {
|
|
ty::UpvarCapture::ByValue => {
|
|
let mode = copy_or_move(&self.mc, self.param_env, &cmt_var);
|
|
self.delegate.consume(&cmt_var, mode);
|
|
}
|
|
ty::UpvarCapture::ByRef(upvar_borrow) => {
|
|
self.delegate.borrow(&cmt_var, upvar_borrow.kind);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn cat_captured_var(&mut self,
|
|
closure_hir_id: hir::HirId,
|
|
closure_span: Span,
|
|
var_id: hir::HirId)
|
|
-> mc::McResult<mc::cmt_<'tcx>> {
|
|
// Create the cmt for the variable being borrowed, from the
|
|
// perspective of the creator (parent) of the closure.
|
|
let var_ty = self.mc.node_ty(var_id)?;
|
|
self.mc.cat_res(closure_hir_id, closure_span, var_ty, Res::Local(var_id))
|
|
}
|
|
}
|
|
|
|
fn copy_or_move<'a, 'tcx>(
|
|
mc: &mc::MemCategorizationContext<'a, 'tcx>,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
cmt: &mc::cmt_<'tcx>,
|
|
) -> ConsumeMode {
|
|
if !mc.type_is_copy_modulo_regions(param_env, cmt.ty, cmt.span) {
|
|
Move
|
|
} else {
|
|
Copy
|
|
}
|
|
}
|