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Commit | Line | Data |
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9fa01778 | 1 | //! A classic liveness analysis based on dataflow over the AST. Computes, |
1a4d82fc | 2 | //! for each local variable in a function, whether that variable is live |
9fa01778 XL |
3 | //! at a given point. Program execution points are identified by their |
4 | //! IDs. | |
1a4d82fc JJ |
5 | //! |
6 | //! # Basic idea | |
7 | //! | |
9fa01778 | 8 | //! The basic model is that each local variable is assigned an index. We |
1a4d82fc | 9 | //! represent sets of local variables using a vector indexed by this |
9fa01778 XL |
10 | //! index. The value in the vector is either 0, indicating the variable |
11 | //! is dead, or the ID of an expression that uses the variable. | |
1a4d82fc | 12 | //! |
9fa01778 XL |
13 | //! We conceptually walk over the AST in reverse execution order. If we |
14 | //! find a use of a variable, we add it to the set of live variables. If | |
1a4d82fc | 15 | //! we find an assignment to a variable, we remove it from the set of live |
9fa01778 XL |
16 | //! variables. When we have to merge two flows, we take the union of |
17 | //! those two flows -- if the variable is live on both paths, we simply | |
18 | //! pick one ID. In the event of loops, we continue doing this until a | |
1a4d82fc JJ |
19 | //! fixed point is reached. |
20 | //! | |
21 | //! ## Checking initialization | |
22 | //! | |
9fa01778 XL |
23 | //! At the function entry point, all variables must be dead. If this is |
24 | //! not the case, we can report an error using the ID found in the set of | |
1a4d82fc JJ |
25 | //! live variables, which identifies a use of the variable which is not |
26 | //! dominated by an assignment. | |
27 | //! | |
28 | //! ## Checking moves | |
29 | //! | |
30 | //! After each explicit move, the variable must be dead. | |
31 | //! | |
32 | //! ## Computing last uses | |
33 | //! | |
34 | //! Any use of the variable where the variable is dead afterwards is a | |
35 | //! last use. | |
36 | //! | |
37 | //! # Implementation details | |
38 | //! | |
39 | //! The actual implementation contains two (nested) walks over the AST. | |
40 | //! The outer walk has the job of building up the ir_maps instance for the | |
9fa01778 | 41 | //! enclosing function. On the way down the tree, it identifies those AST |
1a4d82fc | 42 | //! nodes and variable IDs that will be needed for the liveness analysis |
9fa01778 XL |
43 | //! and assigns them contiguous IDs. The liveness ID for an AST node is |
44 | //! called a `live_node` (it's a newtype'd `u32`) and the ID for a variable | |
45 | //! is called a `variable` (another newtype'd `u32`). | |
1a4d82fc JJ |
46 | //! |
47 | //! On the way back up the tree, as we are about to exit from a function | |
9fa01778 | 48 | //! declaration we allocate a `liveness` instance. Now that we know |
1a4d82fc | 49 | //! precisely how many nodes and variables we need, we can allocate all |
9fa01778 | 50 | //! the various arrays that we will need to precisely the right size. We then |
1a4d82fc JJ |
51 | //! perform the actual propagation on the `liveness` instance. |
52 | //! | |
53 | //! This propagation is encoded in the various `propagate_through_*()` | |
9fa01778 | 54 | //! methods. It effectively does a reverse walk of the AST; whenever we |
1a4d82fc JJ |
55 | //! reach a loop node, we iterate until a fixed point is reached. |
56 | //! | |
0bf4aa26 | 57 | //! ## The `RWU` struct |
1a4d82fc JJ |
58 | //! |
59 | //! At each live node `N`, we track three pieces of information for each | |
0bf4aa26 | 60 | //! variable `V` (these are encapsulated in the `RWU` struct): |
1a4d82fc JJ |
61 | //! |
62 | //! - `reader`: the `LiveNode` ID of some node which will read the value | |
9fa01778 | 63 | //! that `V` holds on entry to `N`. Formally: a node `M` such |
1a4d82fc | 64 | //! that there exists a path `P` from `N` to `M` where `P` does not |
1b1a35ee | 65 | //! write `V`. If the `reader` is `None`, then the current |
1a4d82fc JJ |
66 | //! value will never be read (the variable is dead, essentially). |
67 | //! | |
68 | //! - `writer`: the `LiveNode` ID of some node which will write the | |
9fa01778 | 69 | //! variable `V` and which is reachable from `N`. Formally: a node `M` |
1a4d82fc | 70 | //! such that there exists a path `P` from `N` to `M` and `M` writes |
1b1a35ee | 71 | //! `V`. If the `writer` is `None`, then there is no writer |
1a4d82fc JJ |
72 | //! of `V` that follows `N`. |
73 | //! | |
9fa01778 | 74 | //! - `used`: a boolean value indicating whether `V` is *used*. We |
1a4d82fc | 75 | //! distinguish a *read* from a *use* in that a *use* is some read that |
9fa01778 XL |
76 | //! is not just used to generate a new value. For example, `x += 1` is |
77 | //! a read but not a use. This is used to generate better warnings. | |
1a4d82fc | 78 | //! |
f9f354fc | 79 | //! ## Special nodes and variables |
1a4d82fc | 80 | //! |
f9f354fc | 81 | //! We generate various special nodes for various, well, special purposes. |
1b1a35ee | 82 | //! These are described in the `Liveness` struct. |
b7449926 | 83 | |
1a4d82fc JJ |
84 | use self::LiveNodeKind::*; |
85 | use self::VarKind::*; | |
86 | ||
3dfed10e | 87 | use rustc_ast::InlineAsmOptions; |
e74abb32 | 88 | use rustc_data_structures::fx::FxIndexMap; |
dfeec247 XL |
89 | use rustc_errors::Applicability; |
90 | use rustc_hir as hir; | |
91 | use rustc_hir::def::*; | |
f035d41b | 92 | use rustc_hir::def_id::LocalDefId; |
5099ac24 | 93 | use rustc_hir::intravisit::{self, Visitor}; |
1b1a35ee XL |
94 | use rustc_hir::{Expr, HirId, HirIdMap, HirIdSet}; |
95 | use rustc_index::vec::IndexVec; | |
5099ac24 | 96 | use rustc_middle::hir::nested_filter; |
ba9703b0 | 97 | use rustc_middle::ty::query::Providers; |
94222f64 | 98 | use rustc_middle::ty::{self, DefIdTree, RootVariableMinCaptureList, Ty, TyCtxt}; |
ba9703b0 | 99 | use rustc_session::lint; |
1b1a35ee | 100 | use rustc_span::symbol::{kw, sym, Symbol}; |
dfeec247 | 101 | use rustc_span::Span; |
dfeec247 | 102 | |
e74abb32 | 103 | use std::collections::VecDeque; |
c34b1796 | 104 | use std::io; |
dfeec247 | 105 | use std::io::prelude::*; |
c34b1796 | 106 | use std::rc::Rc; |
e9174d1e | 107 | |
fc512014 XL |
108 | mod rwu_table; |
109 | ||
1b1a35ee XL |
110 | rustc_index::newtype_index! { |
111 | pub struct Variable { | |
112 | DEBUG_FORMAT = "v({})", | |
dfeec247 | 113 | } |
1a4d82fc JJ |
114 | } |
115 | ||
1b1a35ee XL |
116 | rustc_index::newtype_index! { |
117 | pub struct LiveNode { | |
118 | DEBUG_FORMAT = "ln({})", | |
dfeec247 | 119 | } |
1a4d82fc JJ |
120 | } |
121 | ||
c34b1796 | 122 | #[derive(Copy, Clone, PartialEq, Debug)] |
223e47cc | 123 | enum LiveNodeKind { |
48663c56 | 124 | UpvarNode(Span), |
94222f64 XL |
125 | ExprNode(Span, HirId), |
126 | VarDefNode(Span, HirId), | |
f9f354fc | 127 | ClosureNode, |
dfeec247 | 128 | ExitNode, |
223e47cc LB |
129 | } |
130 | ||
dc9dc135 | 131 | fn live_node_kind_to_string(lnk: LiveNodeKind, tcx: TyCtxt<'_>) -> String { |
74b04a01 | 132 | let sm = tcx.sess.source_map(); |
223e47cc | 133 | match lnk { |
17df50a5 | 134 | UpvarNode(s) => format!("Upvar node [{}]", sm.span_to_diagnostic_string(s)), |
94222f64 XL |
135 | ExprNode(s, _) => format!("Expr node [{}]", sm.span_to_diagnostic_string(s)), |
136 | VarDefNode(s, _) => format!("Var def node [{}]", sm.span_to_diagnostic_string(s)), | |
f9f354fc | 137 | ClosureNode => "Closure node".to_owned(), |
0bf4aa26 | 138 | ExitNode => "Exit node".to_owned(), |
223e47cc LB |
139 | } |
140 | } | |
141 | ||
f035d41b | 142 | fn check_mod_liveness(tcx: TyCtxt<'_>, module_def_id: LocalDefId) { |
1b1a35ee | 143 | tcx.hir().visit_item_likes_in_module(module_def_id, &mut IrMaps::new(tcx).as_deep_visitor()); |
9fa01778 XL |
144 | } |
145 | ||
f035d41b | 146 | pub fn provide(providers: &mut Providers) { |
dfeec247 | 147 | *providers = Providers { check_mod_liveness, ..*providers }; |
223e47cc LB |
148 | } |
149 | ||
223e47cc LB |
150 | // ______________________________________________________________________ |
151 | // Creating ir_maps | |
152 | // | |
153 | // This is the first pass and the one that drives the main | |
154 | // computation. It walks up and down the IR once. On the way down, | |
155 | // we count for each function the number of variables as well as | |
156 | // liveness nodes. A liveness node is basically an expression or | |
157 | // capture clause that does something of interest: either it has | |
158 | // interesting control flow or it uses/defines a local variable. | |
159 | // | |
160 | // On the way back up, at each function node we create liveness sets | |
161 | // (we now know precisely how big to make our various vectors and so | |
162 | // forth) and then do the data-flow propagation to compute the set | |
163 | // of live variables at each program point. | |
164 | // | |
165 | // Finally, we run back over the IR one last time and, using the | |
166 | // computed liveness, check various safety conditions. For example, | |
167 | // there must be no live nodes at the definition site for a variable | |
168 | // unless it has an initializer. Similarly, each non-mutable local | |
169 | // variable must not be assigned if there is some successor | |
170 | // assignment. And so forth. | |
171 | ||
223e47cc LB |
172 | struct CaptureInfo { |
173 | ln: LiveNode, | |
dfeec247 | 174 | var_hid: HirId, |
223e47cc LB |
175 | } |
176 | ||
c34b1796 | 177 | #[derive(Copy, Clone, Debug)] |
223e47cc | 178 | struct LocalInfo { |
94b46f34 | 179 | id: HirId, |
f9f354fc | 180 | name: Symbol, |
2c00a5a8 | 181 | is_shorthand: bool, |
223e47cc LB |
182 | } |
183 | ||
c34b1796 | 184 | #[derive(Copy, Clone, Debug)] |
223e47cc | 185 | enum VarKind { |
f9f354fc | 186 | Param(HirId, Symbol), |
223e47cc | 187 | Local(LocalInfo), |
f9f354fc | 188 | Upvar(HirId, Symbol), |
223e47cc LB |
189 | } |
190 | ||
dc9dc135 XL |
191 | struct IrMaps<'tcx> { |
192 | tcx: TyCtxt<'tcx>, | |
94b46f34 XL |
193 | live_node_map: HirIdMap<LiveNode>, |
194 | variable_map: HirIdMap<Variable>, | |
532ac7d7 | 195 | capture_info_map: HirIdMap<Rc<Vec<CaptureInfo>>>, |
1b1a35ee XL |
196 | var_kinds: IndexVec<Variable, VarKind>, |
197 | lnks: IndexVec<LiveNode, LiveNodeKind>, | |
223e47cc LB |
198 | } |
199 | ||
a2a8927a | 200 | impl<'tcx> IrMaps<'tcx> { |
1b1a35ee | 201 | fn new(tcx: TyCtxt<'tcx>) -> IrMaps<'tcx> { |
1a4d82fc | 202 | IrMaps { |
041b39d2 | 203 | tcx, |
a1dfa0c6 XL |
204 | live_node_map: HirIdMap::default(), |
205 | variable_map: HirIdMap::default(), | |
206 | capture_info_map: Default::default(), | |
1b1a35ee XL |
207 | var_kinds: IndexVec::new(), |
208 | lnks: IndexVec::new(), | |
1a4d82fc | 209 | } |
223e47cc | 210 | } |
223e47cc | 211 | |
1a4d82fc | 212 | fn add_live_node(&mut self, lnk: LiveNodeKind) -> LiveNode { |
1b1a35ee | 213 | let ln = self.lnks.push(lnk); |
223e47cc | 214 | |
dfeec247 | 215 | debug!("{:?} is of kind {}", ln, live_node_kind_to_string(lnk, self.tcx)); |
223e47cc LB |
216 | |
217 | ln | |
218 | } | |
219 | ||
94b46f34 | 220 | fn add_live_node_for_node(&mut self, hir_id: HirId, lnk: LiveNodeKind) { |
223e47cc | 221 | let ln = self.add_live_node(lnk); |
94b46f34 | 222 | self.live_node_map.insert(hir_id, ln); |
223e47cc | 223 | |
94b46f34 | 224 | debug!("{:?} is node {:?}", ln, hir_id); |
223e47cc LB |
225 | } |
226 | ||
1a4d82fc | 227 | fn add_variable(&mut self, vk: VarKind) -> Variable { |
1b1a35ee | 228 | let v = self.var_kinds.push(vk); |
223e47cc LB |
229 | |
230 | match vk { | |
f9f354fc | 231 | Local(LocalInfo { id: node_id, .. }) | Param(node_id, _) | Upvar(node_id, _) => { |
223e47cc | 232 | self.variable_map.insert(node_id, v); |
dfeec247 | 233 | } |
223e47cc LB |
234 | } |
235 | ||
1a4d82fc | 236 | debug!("{:?} is {:?}", v, vk); |
223e47cc LB |
237 | |
238 | v | |
239 | } | |
240 | ||
94b46f34 XL |
241 | fn variable(&self, hir_id: HirId, span: Span) -> Variable { |
242 | match self.variable_map.get(&hir_id) { | |
54a0048b SL |
243 | Some(&var) => var, |
244 | None => { | |
94b46f34 | 245 | span_bug!(span, "no variable registered for id {:?}", hir_id); |
54a0048b | 246 | } |
223e47cc LB |
247 | } |
248 | } | |
249 | ||
1b1a35ee XL |
250 | fn variable_name(&self, var: Variable) -> Symbol { |
251 | match self.var_kinds[var] { | |
252 | Local(LocalInfo { name, .. }) | Param(_, name) | Upvar(_, name) => name, | |
223e47cc LB |
253 | } |
254 | } | |
255 | ||
2c00a5a8 | 256 | fn variable_is_shorthand(&self, var: Variable) -> bool { |
1b1a35ee | 257 | match self.var_kinds[var] { |
2c00a5a8 | 258 | Local(LocalInfo { is_shorthand, .. }) => is_shorthand, |
f9f354fc | 259 | Param(..) | Upvar(..) => false, |
2c00a5a8 XL |
260 | } |
261 | } | |
262 | ||
532ac7d7 XL |
263 | fn set_captures(&mut self, hir_id: HirId, cs: Vec<CaptureInfo>) { |
264 | self.capture_info_map.insert(hir_id, Rc::new(cs)); | |
223e47cc LB |
265 | } |
266 | ||
c295e0f8 | 267 | fn collect_shorthand_field_ids(&self, pat: &hir::Pat<'tcx>) -> HirIdSet { |
1b1a35ee XL |
268 | // For struct patterns, take note of which fields used shorthand |
269 | // (`x` rather than `x: x`). | |
270 | let mut shorthand_field_ids = HirIdSet::default(); | |
271 | let mut pats = VecDeque::new(); | |
272 | pats.push_back(pat); | |
c295e0f8 | 273 | |
1b1a35ee XL |
274 | while let Some(pat) = pats.pop_front() { |
275 | use rustc_hir::PatKind::*; | |
276 | match &pat.kind { | |
277 | Binding(.., inner_pat) => { | |
278 | pats.extend(inner_pat.iter()); | |
279 | } | |
280 | Struct(_, fields, _) => { | |
c295e0f8 XL |
281 | let (short, not_short): (Vec<&_>, Vec<&_>) = |
282 | fields.iter().partition(|f| f.is_shorthand); | |
283 | shorthand_field_ids.extend(short.iter().map(|f| f.pat.hir_id)); | |
284 | pats.extend(not_short.iter().map(|f| f.pat)); | |
1b1a35ee XL |
285 | } |
286 | Ref(inner_pat, _) | Box(inner_pat) => { | |
287 | pats.push_back(inner_pat); | |
288 | } | |
289 | TupleStruct(_, inner_pats, _) | Tuple(inner_pats, _) | Or(inner_pats) => { | |
290 | pats.extend(inner_pats.iter()); | |
291 | } | |
292 | Slice(pre_pats, inner_pat, post_pats) => { | |
293 | pats.extend(pre_pats.iter()); | |
294 | pats.extend(inner_pat.iter()); | |
295 | pats.extend(post_pats.iter()); | |
296 | } | |
297 | _ => {} | |
298 | } | |
299 | } | |
300 | ||
c295e0f8 XL |
301 | return shorthand_field_ids; |
302 | } | |
303 | ||
304 | fn add_from_pat(&mut self, pat: &hir::Pat<'tcx>) { | |
305 | let shorthand_field_ids = self.collect_shorthand_field_ids(pat); | |
306 | ||
1b1a35ee | 307 | pat.each_binding(|_, hir_id, _, ident| { |
94222f64 | 308 | self.add_live_node_for_node(hir_id, VarDefNode(ident.span, hir_id)); |
1b1a35ee XL |
309 | self.add_variable(Local(LocalInfo { |
310 | id: hir_id, | |
311 | name: ident.name, | |
312 | is_shorthand: shorthand_field_ids.contains(&hir_id), | |
313 | })); | |
314 | }); | |
223e47cc | 315 | } |
1a4d82fc | 316 | } |
223e47cc | 317 | |
1b1a35ee | 318 | impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> { |
5099ac24 | 319 | type NestedFilter = nested_filter::OnlyBodies; |
1b1a35ee | 320 | |
5099ac24 FG |
321 | fn nested_visit_map(&mut self) -> Self::Map { |
322 | self.tcx.hir() | |
83c7162d XL |
323 | } |
324 | ||
1b1a35ee XL |
325 | fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) { |
326 | debug!("visit_body {:?}", body.id()); | |
223e47cc | 327 | |
1b1a35ee XL |
328 | // swap in a new set of IR maps for this body |
329 | let mut maps = IrMaps::new(self.tcx); | |
330 | let hir_id = maps.tcx.hir().body_owner(body.id()); | |
fc512014 XL |
331 | let local_def_id = maps.tcx.hir().local_def_id(hir_id); |
332 | let def_id = local_def_id.to_def_id(); | |
32a655c1 | 333 | |
1b1a35ee | 334 | // Don't run unused pass for #[derive()] |
5e7ed085 FG |
335 | if let Some(parent) = self.tcx.parent(def_id) |
336 | && let DefKind::Impl = self.tcx.def_kind(parent.expect_local()) | |
337 | && self.tcx.has_attr(parent, sym::automatically_derived) | |
338 | { | |
339 | return; | |
f9f354fc | 340 | } |
1b1a35ee | 341 | |
94222f64 XL |
342 | // Don't run unused pass for #[naked] |
343 | if self.tcx.has_attr(def_id, sym::naked) { | |
344 | return; | |
345 | } | |
346 | ||
347 | if let Some(upvars) = maps.tcx.upvars_mentioned(def_id) { | |
348 | for &var_hir_id in upvars.keys() { | |
1b1a35ee XL |
349 | let var_name = maps.tcx.hir().name(var_hir_id); |
350 | maps.add_variable(Upvar(var_hir_id, var_name)); | |
351 | } | |
352 | } | |
353 | ||
354 | // gather up the various local variables, significant expressions, | |
355 | // and so forth: | |
356 | intravisit::walk_body(&mut maps, body); | |
357 | ||
358 | // compute liveness | |
fc512014 | 359 | let mut lsets = Liveness::new(&mut maps, local_def_id); |
1b1a35ee XL |
360 | let entry_ln = lsets.compute(&body, hir_id); |
361 | lsets.log_liveness(entry_ln, body.id().hir_id); | |
362 | ||
363 | // check for various error conditions | |
364 | lsets.visit_body(body); | |
365 | lsets.warn_about_unused_upvars(entry_ln); | |
366 | lsets.warn_about_unused_args(body, entry_ln); | |
367 | } | |
368 | ||
369 | fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) { | |
370 | self.add_from_pat(&local.pat); | |
371 | intravisit::walk_local(self, local); | |
372 | } | |
373 | ||
374 | fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) { | |
375 | self.add_from_pat(&arm.pat); | |
fc512014 XL |
376 | if let Some(hir::Guard::IfLet(ref pat, _)) = arm.guard { |
377 | self.add_from_pat(pat); | |
378 | } | |
1b1a35ee | 379 | intravisit::walk_arm(self, arm); |
f9f354fc XL |
380 | } |
381 | ||
1b1a35ee | 382 | fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) { |
c295e0f8 | 383 | let shorthand_field_ids = self.collect_shorthand_field_ids(param.pat); |
e1599b0c | 384 | param.pat.each_binding(|_bm, hir_id, _x, ident| { |
6a06907d | 385 | let var = match param.pat.kind { |
c295e0f8 | 386 | rustc_hir::PatKind::Struct(..) => Local(LocalInfo { |
6a06907d XL |
387 | id: hir_id, |
388 | name: ident.name, | |
c295e0f8 | 389 | is_shorthand: shorthand_field_ids.contains(&hir_id), |
6a06907d XL |
390 | }), |
391 | _ => Param(hir_id, ident.name), | |
532ac7d7 | 392 | }; |
1b1a35ee XL |
393 | self.add_variable(var); |
394 | }); | |
395 | intravisit::walk_param(self, param); | |
dfeec247 | 396 | } |
223e47cc | 397 | |
1b1a35ee XL |
398 | fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { |
399 | match expr.kind { | |
400 | // live nodes required for uses or definitions of variables: | |
401 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { | |
402 | debug!("expr {}: path that leads to {:?}", expr.hir_id, path.res); | |
403 | if let Res::Local(_var_hir_id) = path.res { | |
94222f64 | 404 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id)); |
1b1a35ee XL |
405 | } |
406 | intravisit::walk_expr(self, expr); | |
94b46f34 | 407 | } |
1b1a35ee XL |
408 | hir::ExprKind::Closure(..) => { |
409 | // Interesting control flow (for loops can contain labeled | |
410 | // breaks or continues) | |
94222f64 | 411 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id)); |
1b1a35ee | 412 | |
94222f64 | 413 | // Make a live_node for each mentioned variable, with the span |
1b1a35ee XL |
414 | // being the location that the variable is used. This results |
415 | // in better error messages than just pointing at the closure | |
416 | // construction site. | |
417 | let mut call_caps = Vec::new(); | |
418 | let closure_def_id = self.tcx.hir().local_def_id(expr.hir_id); | |
94222f64 XL |
419 | if let Some(upvars) = self.tcx.upvars_mentioned(closure_def_id) { |
420 | call_caps.extend(upvars.keys().map(|var_id| { | |
fc512014 | 421 | let upvar = upvars[var_id]; |
1b1a35ee | 422 | let upvar_ln = self.add_live_node(UpvarNode(upvar.span)); |
fc512014 | 423 | CaptureInfo { ln: upvar_ln, var_hid: *var_id } |
1b1a35ee XL |
424 | })); |
425 | } | |
426 | self.set_captures(expr.hir_id, call_caps); | |
427 | intravisit::walk_expr(self, expr); | |
94b46f34 | 428 | } |
94b46f34 | 429 | |
a2a8927a XL |
430 | hir::ExprKind::Let(let_expr) => { |
431 | self.add_from_pat(let_expr.pat); | |
94222f64 XL |
432 | intravisit::walk_expr(self, expr); |
433 | } | |
434 | ||
1b1a35ee | 435 | // live nodes required for interesting control flow: |
94222f64 XL |
436 | hir::ExprKind::If(..) |
437 | | hir::ExprKind::Match(..) | |
438 | | hir::ExprKind::Loop(..) | |
439 | | hir::ExprKind::Yield(..) => { | |
440 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id)); | |
1b1a35ee | 441 | intravisit::walk_expr(self, expr); |
dc9dc135 | 442 | } |
1b1a35ee | 443 | hir::ExprKind::Binary(op, ..) if op.node.is_lazy() => { |
94222f64 | 444 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id)); |
1b1a35ee | 445 | intravisit::walk_expr(self, expr); |
dfeec247 | 446 | } |
dfeec247 | 447 | |
1b1a35ee XL |
448 | // otherwise, live nodes are not required: |
449 | hir::ExprKind::Index(..) | |
450 | | hir::ExprKind::Field(..) | |
451 | | hir::ExprKind::Array(..) | |
452 | | hir::ExprKind::Call(..) | |
453 | | hir::ExprKind::MethodCall(..) | |
454 | | hir::ExprKind::Tup(..) | |
455 | | hir::ExprKind::Binary(..) | |
456 | | hir::ExprKind::AddrOf(..) | |
457 | | hir::ExprKind::Cast(..) | |
458 | | hir::ExprKind::DropTemps(..) | |
459 | | hir::ExprKind::Unary(..) | |
460 | | hir::ExprKind::Break(..) | |
461 | | hir::ExprKind::Continue(_) | |
462 | | hir::ExprKind::Lit(_) | |
29967ef6 | 463 | | hir::ExprKind::ConstBlock(..) |
1b1a35ee XL |
464 | | hir::ExprKind::Ret(..) |
465 | | hir::ExprKind::Block(..) | |
466 | | hir::ExprKind::Assign(..) | |
467 | | hir::ExprKind::AssignOp(..) | |
468 | | hir::ExprKind::Struct(..) | |
469 | | hir::ExprKind::Repeat(..) | |
470 | | hir::ExprKind::InlineAsm(..) | |
1b1a35ee | 471 | | hir::ExprKind::Box(..) |
1b1a35ee XL |
472 | | hir::ExprKind::Type(..) |
473 | | hir::ExprKind::Err | |
474 | | hir::ExprKind::Path(hir::QPath::TypeRelative(..)) | |
475 | | hir::ExprKind::Path(hir::QPath::LangItem(..)) => { | |
476 | intravisit::walk_expr(self, expr); | |
477 | } | |
48663c56 | 478 | } |
223e47cc LB |
479 | } |
480 | } | |
481 | ||
482 | // ______________________________________________________________________ | |
483 | // Computing liveness sets | |
484 | // | |
485 | // Actually we compute just a bit more than just liveness, but we use | |
486 | // the same basic propagation framework in all cases. | |
487 | ||
c34b1796 AL |
488 | const ACC_READ: u32 = 1; |
489 | const ACC_WRITE: u32 = 2; | |
490 | const ACC_USE: u32 = 4; | |
223e47cc | 491 | |
dc9dc135 XL |
492 | struct Liveness<'a, 'tcx> { |
493 | ir: &'a mut IrMaps<'tcx>, | |
3dfed10e | 494 | typeck_results: &'a ty::TypeckResults<'tcx>, |
ba9703b0 | 495 | param_env: ty::ParamEnv<'tcx>, |
6a06907d | 496 | closure_min_captures: Option<&'tcx RootVariableMinCaptureList<'tcx>>, |
1b1a35ee | 497 | successors: IndexVec<LiveNode, Option<LiveNode>>, |
fc512014 | 498 | rwu_table: rwu_table::RWUTable, |
cc61c64b | 499 | |
1b1a35ee XL |
500 | /// A live node representing a point of execution before closure entry & |
501 | /// after closure exit. Used to calculate liveness of captured variables | |
502 | /// through calls to the same closure. Used for Fn & FnMut closures only. | |
503 | closure_ln: LiveNode, | |
504 | /// A live node representing every 'exit' from the function, whether it be | |
505 | /// by explicit return, panic, or other means. | |
506 | exit_ln: LiveNode, | |
507 | ||
223e47cc LB |
508 | // mappings from loop node ID to LiveNode |
509 | // ("break" label should map to loop node ID, | |
510 | // it probably doesn't now) | |
532ac7d7 XL |
511 | break_ln: HirIdMap<LiveNode>, |
512 | cont_ln: HirIdMap<LiveNode>, | |
223e47cc LB |
513 | } |
514 | ||
1a4d82fc | 515 | impl<'a, 'tcx> Liveness<'a, 'tcx> { |
1b1a35ee XL |
516 | fn new(ir: &'a mut IrMaps<'tcx>, body_owner: LocalDefId) -> Liveness<'a, 'tcx> { |
517 | let typeck_results = ir.tcx.typeck(body_owner); | |
518 | let param_env = ir.tcx.param_env(body_owner); | |
6a06907d | 519 | let closure_min_captures = typeck_results.closure_min_captures.get(&body_owner.to_def_id()); |
1b1a35ee XL |
520 | let closure_ln = ir.add_live_node(ClosureNode); |
521 | let exit_ln = ir.add_live_node(ExitNode); | |
32a655c1 | 522 | |
1b1a35ee XL |
523 | let num_live_nodes = ir.lnks.len(); |
524 | let num_vars = ir.var_kinds.len(); | |
32a655c1 | 525 | |
1a4d82fc | 526 | Liveness { |
041b39d2 | 527 | ir, |
3dfed10e | 528 | typeck_results, |
ba9703b0 | 529 | param_env, |
6a06907d | 530 | closure_min_captures, |
1b1a35ee | 531 | successors: IndexVec::from_elem_n(None, num_live_nodes), |
fc512014 | 532 | rwu_table: rwu_table::RWUTable::new(num_live_nodes, num_vars), |
1b1a35ee XL |
533 | closure_ln, |
534 | exit_ln, | |
a1dfa0c6 XL |
535 | break_ln: Default::default(), |
536 | cont_ln: Default::default(), | |
1a4d82fc | 537 | } |
223e47cc | 538 | } |
223e47cc | 539 | |
94b46f34 XL |
540 | fn live_node(&self, hir_id: HirId, span: Span) -> LiveNode { |
541 | match self.ir.live_node_map.get(&hir_id) { | |
dfeec247 XL |
542 | Some(&ln) => ln, |
543 | None => { | |
544 | // This must be a mismatch between the ir_map construction | |
545 | // above and the propagation code below; the two sets of | |
546 | // code have to agree about which AST nodes are worth | |
547 | // creating liveness nodes for. | |
548 | span_bug!(span, "no live node registered for node {:?}", hir_id); | |
549 | } | |
223e47cc LB |
550 | } |
551 | } | |
552 | ||
94b46f34 XL |
553 | fn variable(&self, hir_id: HirId, span: Span) -> Variable { |
554 | self.ir.variable(hir_id, span) | |
223e47cc LB |
555 | } |
556 | ||
dfeec247 | 557 | fn define_bindings_in_pat(&mut self, pat: &hir::Pat<'_>, mut succ: LiveNode) -> LiveNode { |
e74abb32 XL |
558 | // In an or-pattern, only consider the first pattern; any later patterns |
559 | // must have the same bindings, and we also consider the first pattern | |
560 | // to be the "authoritative" set of ids. | |
561 | pat.each_binding_or_first(&mut |_, hir_id, pat_sp, ident| { | |
562 | let ln = self.live_node(hir_id, pat_sp); | |
563 | let var = self.variable(hir_id, ident.span); | |
564 | self.init_from_succ(ln, succ); | |
565 | self.define(ln, var); | |
223e47cc | 566 | succ = ln; |
1a4d82fc | 567 | }); |
223e47cc LB |
568 | succ |
569 | } | |
570 | ||
fc512014 XL |
571 | fn live_on_entry(&self, ln: LiveNode, var: Variable) -> bool { |
572 | self.rwu_table.get_reader(ln, var) | |
223e47cc LB |
573 | } |
574 | ||
0bf4aa26 | 575 | // Is this variable live on entry to any of its successor nodes? |
fc512014 | 576 | fn live_on_exit(&self, ln: LiveNode, var: Variable) -> bool { |
1b1a35ee | 577 | let successor = self.successors[ln].unwrap(); |
1a4d82fc | 578 | self.live_on_entry(successor, var) |
223e47cc LB |
579 | } |
580 | ||
1a4d82fc | 581 | fn used_on_entry(&self, ln: LiveNode, var: Variable) -> bool { |
fc512014 | 582 | self.rwu_table.get_used(ln, var) |
223e47cc LB |
583 | } |
584 | ||
fc512014 XL |
585 | fn assigned_on_entry(&self, ln: LiveNode, var: Variable) -> bool { |
586 | self.rwu_table.get_writer(ln, var) | |
223e47cc LB |
587 | } |
588 | ||
fc512014 | 589 | fn assigned_on_exit(&self, ln: LiveNode, var: Variable) -> bool { |
1b1a35ee | 590 | let successor = self.successors[ln].unwrap(); |
1a4d82fc | 591 | self.assigned_on_entry(successor, var) |
223e47cc LB |
592 | } |
593 | ||
fc512014 | 594 | fn write_vars<F>(&self, wr: &mut dyn Write, mut test: F) -> io::Result<()> |
dfeec247 | 595 | where |
fc512014 | 596 | F: FnMut(Variable) -> bool, |
1a4d82fc | 597 | { |
1b1a35ee | 598 | for var_idx in 0..self.ir.var_kinds.len() { |
fc512014 XL |
599 | let var = Variable::from(var_idx); |
600 | if test(var) { | |
601 | write!(wr, " {:?}", var)?; | |
223e47cc LB |
602 | } |
603 | } | |
1a4d82fc | 604 | Ok(()) |
223e47cc LB |
605 | } |
606 | ||
1a4d82fc JJ |
607 | #[allow(unused_must_use)] |
608 | fn ln_str(&self, ln: LiveNode) -> String { | |
609 | let mut wr = Vec::new(); | |
610 | { | |
0531ce1d | 611 | let wr = &mut wr as &mut dyn Write; |
1b1a35ee | 612 | write!(wr, "[{:?} of kind {:?} reads", ln, self.ir.lnks[ln]); |
fc512014 | 613 | self.write_vars(wr, |var| self.rwu_table.get_reader(ln, var)); |
1a4d82fc | 614 | write!(wr, " writes"); |
fc512014 | 615 | self.write_vars(wr, |var| self.rwu_table.get_writer(ln, var)); |
f9f354fc | 616 | write!(wr, " uses"); |
fc512014 | 617 | self.write_vars(wr, |var| self.rwu_table.get_used(ln, var)); |
f9f354fc | 618 | |
1b1a35ee | 619 | write!(wr, " precedes {:?}]", self.successors[ln]); |
223e47cc | 620 | } |
1a4d82fc | 621 | String::from_utf8(wr).unwrap() |
223e47cc LB |
622 | } |
623 | ||
f9f354fc XL |
624 | fn log_liveness(&self, entry_ln: LiveNode, hir_id: hir::HirId) { |
625 | // hack to skip the loop unless debug! is enabled: | |
626 | debug!( | |
627 | "^^ liveness computation results for body {} (entry={:?})", | |
628 | { | |
1b1a35ee XL |
629 | for ln_idx in 0..self.ir.lnks.len() { |
630 | debug!("{:?}", self.ln_str(LiveNode::from(ln_idx))); | |
f9f354fc XL |
631 | } |
632 | hir_id | |
633 | }, | |
634 | entry_ln | |
635 | ); | |
636 | } | |
637 | ||
1a4d82fc | 638 | fn init_empty(&mut self, ln: LiveNode, succ_ln: LiveNode) { |
1b1a35ee | 639 | self.successors[ln] = Some(succ_ln); |
223e47cc | 640 | |
0bf4aa26 | 641 | // It is not necessary to initialize the RWUs here because they are all |
fc512014 | 642 | // empty when created, and the sets only grow during iterations. |
223e47cc LB |
643 | } |
644 | ||
1a4d82fc | 645 | fn init_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode) { |
223e47cc | 646 | // more efficient version of init_empty() / merge_from_succ() |
1b1a35ee | 647 | self.successors[ln] = Some(succ_ln); |
fc512014 | 648 | self.rwu_table.copy(ln, succ_ln); |
dfeec247 | 649 | debug!("init_from_succ(ln={}, succ={})", self.ln_str(ln), self.ln_str(succ_ln)); |
223e47cc LB |
650 | } |
651 | ||
fc512014 | 652 | fn merge_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode) -> bool { |
dfeec247 XL |
653 | if ln == succ_ln { |
654 | return false; | |
655 | } | |
223e47cc | 656 | |
fc512014 XL |
657 | let changed = self.rwu_table.union(ln, succ_ln); |
658 | debug!("merge_from_succ(ln={:?}, succ={}, changed={})", ln, self.ln_str(succ_ln), changed); | |
659 | changed | |
223e47cc LB |
660 | } |
661 | ||
662 | // Indicates that a local variable was *defined*; we know that no | |
663 | // uses of the variable can precede the definition (resolve checks | |
664 | // this) so we just clear out all the data. | |
1a4d82fc | 665 | fn define(&mut self, writer: LiveNode, var: Variable) { |
fc512014 XL |
666 | let used = self.rwu_table.get_used(writer, var); |
667 | self.rwu_table.set(writer, var, rwu_table::RWU { reader: false, writer: false, used }); | |
668 | debug!("{:?} defines {:?}: {}", writer, var, self.ln_str(writer)); | |
223e47cc LB |
669 | } |
670 | ||
671 | // Either read, write, or both depending on the acc bitset | |
c34b1796 | 672 | fn acc(&mut self, ln: LiveNode, var: Variable, acc: u32) { |
dfeec247 | 673 | debug!("{:?} accesses[{:x}] {:?}: {}", ln, acc, var, self.ln_str(ln)); |
1a4d82fc | 674 | |
fc512014 | 675 | let mut rwu = self.rwu_table.get(ln, var); |
223e47cc LB |
676 | |
677 | if (acc & ACC_WRITE) != 0 { | |
fc512014 XL |
678 | rwu.reader = false; |
679 | rwu.writer = true; | |
223e47cc LB |
680 | } |
681 | ||
682 | // Important: if we both read/write, must do read second | |
683 | // or else the write will override. | |
684 | if (acc & ACC_READ) != 0 { | |
fc512014 | 685 | rwu.reader = true; |
223e47cc LB |
686 | } |
687 | ||
688 | if (acc & ACC_USE) != 0 { | |
0bf4aa26 | 689 | rwu.used = true; |
223e47cc | 690 | } |
223e47cc | 691 | |
fc512014 | 692 | self.rwu_table.set(ln, var, rwu); |
0bf4aa26 | 693 | } |
223e47cc | 694 | |
1b1a35ee XL |
695 | fn compute(&mut self, body: &hir::Body<'_>, hir_id: HirId) -> LiveNode { |
696 | debug!("compute: for body {:?}", body.id().hir_id); | |
223e47cc | 697 | |
f9f354fc XL |
698 | // # Liveness of captured variables |
699 | // | |
700 | // When computing the liveness for captured variables we take into | |
701 | // account how variable is captured (ByRef vs ByValue) and what is the | |
702 | // closure kind (Generator / FnOnce vs Fn / FnMut). | |
703 | // | |
704 | // Variables captured by reference are assumed to be used on the exit | |
705 | // from the closure. | |
706 | // | |
707 | // In FnOnce closures, variables captured by value are known to be dead | |
708 | // on exit since it is impossible to call the closure again. | |
709 | // | |
710 | // In Fn / FnMut closures, variables captured by value are live on exit | |
711 | // if they are live on the entry to the closure, since only the closure | |
712 | // itself can access them on subsequent calls. | |
713 | ||
6a06907d | 714 | if let Some(closure_min_captures) = self.closure_min_captures { |
f9f354fc | 715 | // Mark upvars captured by reference as used after closure exits. |
6a06907d XL |
716 | for (&var_hir_id, min_capture_list) in closure_min_captures { |
717 | for captured_place in min_capture_list { | |
718 | match captured_place.info.capture_kind { | |
719 | ty::UpvarCapture::ByRef(_) => { | |
720 | let var = self.variable( | |
721 | var_hir_id, | |
722 | captured_place.get_capture_kind_span(self.ir.tcx), | |
723 | ); | |
724 | self.acc(self.exit_ln, var, ACC_READ | ACC_USE); | |
725 | } | |
5099ac24 | 726 | ty::UpvarCapture::ByValue => {} |
f9f354fc | 727 | } |
f9f354fc XL |
728 | } |
729 | } | |
730 | } | |
cc61c64b | 731 | |
1b1a35ee | 732 | let succ = self.propagate_through_expr(&body.value, self.exit_ln); |
223e47cc | 733 | |
6a06907d | 734 | if self.closure_min_captures.is_none() { |
1b1a35ee XL |
735 | // Either not a closure, or closure without any captured variables. |
736 | // No need to determine liveness of captured variables, since there | |
737 | // are none. | |
738 | return succ; | |
f9f354fc XL |
739 | } |
740 | ||
1b1a35ee XL |
741 | let ty = self.typeck_results.node_type(hir_id); |
742 | match ty.kind() { | |
f9f354fc XL |
743 | ty::Closure(_def_id, substs) => match substs.as_closure().kind() { |
744 | ty::ClosureKind::Fn => {} | |
745 | ty::ClosureKind::FnMut => {} | |
746 | ty::ClosureKind::FnOnce => return succ, | |
dfeec247 | 747 | }, |
f9f354fc XL |
748 | ty::Generator(..) => return succ, |
749 | _ => { | |
1b1a35ee XL |
750 | span_bug!( |
751 | body.value.span, | |
752 | "{} has upvars so it should have a closure type: {:?}", | |
753 | hir_id, | |
754 | ty | |
755 | ); | |
f9f354fc XL |
756 | } |
757 | }; | |
758 | ||
759 | // Propagate through calls to the closure. | |
f9f354fc | 760 | loop { |
1b1a35ee | 761 | self.init_from_succ(self.closure_ln, succ); |
f9f354fc XL |
762 | for param in body.params { |
763 | param.pat.each_binding(|_bm, hir_id, _x, ident| { | |
764 | let var = self.variable(hir_id, ident.span); | |
1b1a35ee | 765 | self.define(self.closure_ln, var); |
f9f354fc XL |
766 | }) |
767 | } | |
223e47cc | 768 | |
fc512014 | 769 | if !self.merge_from_succ(self.exit_ln, self.closure_ln) { |
f9f354fc XL |
770 | break; |
771 | } | |
1b1a35ee | 772 | assert_eq!(succ, self.propagate_through_expr(&body.value, self.exit_ln)); |
f9f354fc XL |
773 | } |
774 | ||
775 | succ | |
223e47cc LB |
776 | } |
777 | ||
dfeec247 | 778 | fn propagate_through_block(&mut self, blk: &hir::Block<'_>, succ: LiveNode) -> LiveNode { |
cc61c64b | 779 | if blk.targeted_by_break { |
532ac7d7 | 780 | self.break_ln.insert(blk.hir_id, succ); |
cc61c64b | 781 | } |
c295e0f8 | 782 | let succ = self.propagate_through_opt_expr(blk.expr, succ); |
dfeec247 | 783 | blk.stmts.iter().rev().fold(succ, |succ, stmt| self.propagate_through_stmt(stmt, succ)) |
223e47cc LB |
784 | } |
785 | ||
dfeec247 | 786 | fn propagate_through_stmt(&mut self, stmt: &hir::Stmt<'_>, succ: LiveNode) -> LiveNode { |
e74abb32 | 787 | match stmt.kind { |
9fa01778 XL |
788 | hir::StmtKind::Local(ref local) => { |
789 | // Note: we mark the variable as defined regardless of whether | |
790 | // there is an initializer. Initially I had thought to only mark | |
791 | // the live variable as defined if it was initialized, and then we | |
792 | // could check for uninit variables just by scanning what is live | |
793 | // at the start of the function. But that doesn't work so well for | |
794 | // immutable variables defined in a loop: | |
795 | // loop { let x; x = 5; } | |
796 | // because the "assignment" loops back around and generates an error. | |
797 | // | |
798 | // So now we just check that variables defined w/o an | |
799 | // initializer are not live at the point of their | |
800 | // initialization, which is mildly more complex than checking | |
801 | // once at the func header but otherwise equivalent. | |
223e47cc | 802 | |
c295e0f8 | 803 | let succ = self.propagate_through_opt_expr(local.init, succ); |
9fa01778 | 804 | self.define_bindings_in_pat(&local.pat, succ) |
1a4d82fc | 805 | } |
9fa01778 XL |
806 | hir::StmtKind::Item(..) => succ, |
807 | hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => { | |
808 | self.propagate_through_expr(&expr, succ) | |
223e47cc | 809 | } |
223e47cc LB |
810 | } |
811 | } | |
812 | ||
dfeec247 XL |
813 | fn propagate_through_exprs(&mut self, exprs: &[Expr<'_>], succ: LiveNode) -> LiveNode { |
814 | exprs.iter().rev().fold(succ, |succ, expr| self.propagate_through_expr(&expr, succ)) | |
223e47cc LB |
815 | } |
816 | ||
dfeec247 XL |
817 | fn propagate_through_opt_expr( |
818 | &mut self, | |
819 | opt_expr: Option<&Expr<'_>>, | |
820 | succ: LiveNode, | |
821 | ) -> LiveNode { | |
1a4d82fc | 822 | opt_expr.map_or(succ, |expr| self.propagate_through_expr(expr, succ)) |
223e47cc LB |
823 | } |
824 | ||
dfeec247 | 825 | fn propagate_through_expr(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode { |
ba9703b0 | 826 | debug!("propagate_through_expr: {:?}", expr); |
223e47cc | 827 | |
e74abb32 | 828 | match expr.kind { |
0bf4aa26 XL |
829 | // Interesting cases with control flow or which gen/kill |
830 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { | |
831 | self.access_path(expr.hir_id, path, succ, ACC_READ | ACC_USE) | |
832 | } | |
223e47cc | 833 | |
dfeec247 | 834 | hir::ExprKind::Field(ref e, _) => self.propagate_through_expr(&e, succ), |
1a4d82fc | 835 | |
9fa01778 | 836 | hir::ExprKind::Closure(..) => { |
ba9703b0 | 837 | debug!("{:?} is an ExprKind::Closure", expr); |
0bf4aa26 | 838 | |
0bf4aa26 XL |
839 | // the construction of a closure itself is not important, |
840 | // but we have to consider the closed over variables. | |
dfeec247 XL |
841 | let caps = self |
842 | .ir | |
843 | .capture_info_map | |
844 | .get(&expr.hir_id) | |
845 | .cloned() | |
846 | .unwrap_or_else(|| span_bug!(expr.span, "no registered caps")); | |
0bf4aa26 XL |
847 | |
848 | caps.iter().rev().fold(succ, |succ, cap| { | |
849 | self.init_from_succ(cap.ln, succ); | |
850 | let var = self.variable(cap.var_hid, expr.span); | |
851 | self.acc(cap.ln, var, ACC_READ | ACC_USE); | |
852 | cap.ln | |
853 | }) | |
854 | } | |
223e47cc | 855 | |
a2a8927a XL |
856 | hir::ExprKind::Let(let_expr) => { |
857 | let succ = self.propagate_through_expr(let_expr.init, succ); | |
858 | self.define_bindings_in_pat(let_expr.pat, succ) | |
94222f64 XL |
859 | } |
860 | ||
0bf4aa26 XL |
861 | // Note that labels have been resolved, so we don't need to look |
862 | // at the label ident | |
5869c6ff XL |
863 | hir::ExprKind::Loop(ref blk, ..) => self.propagate_through_loop(expr, &blk, succ), |
864 | ||
94222f64 XL |
865 | hir::ExprKind::Yield(ref e, ..) => { |
866 | let yield_ln = self.live_node(expr.hir_id, expr.span); | |
867 | self.init_from_succ(yield_ln, succ); | |
868 | self.merge_from_succ(yield_ln, self.exit_ln); | |
869 | self.propagate_through_expr(e, yield_ln) | |
870 | } | |
871 | ||
5869c6ff XL |
872 | hir::ExprKind::If(ref cond, ref then, ref else_opt) => { |
873 | // | |
874 | // (cond) | |
875 | // | | |
876 | // v | |
877 | // (expr) | |
878 | // / \ | |
879 | // | | | |
880 | // v v | |
881 | // (then)(els) | |
882 | // | | | |
883 | // v v | |
884 | // ( succ ) | |
885 | // | |
886 | let else_ln = | |
887 | self.propagate_through_opt_expr(else_opt.as_ref().map(|e| &**e), succ); | |
888 | let then_ln = self.propagate_through_expr(&then, succ); | |
889 | let ln = self.live_node(expr.hir_id, expr.span); | |
890 | self.init_from_succ(ln, else_ln); | |
891 | self.merge_from_succ(ln, then_ln); | |
892 | self.propagate_through_expr(&cond, ln) | |
893 | } | |
223e47cc | 894 | |
dfeec247 | 895 | hir::ExprKind::Match(ref e, arms, _) => { |
0bf4aa26 XL |
896 | // |
897 | // (e) | |
898 | // | | |
899 | // v | |
900 | // (expr) | |
901 | // / | \ | |
902 | // | | | | |
903 | // v v v | |
904 | // (..arms..) | |
905 | // | | | | |
906 | // v v v | |
907 | // ( succ ) | |
908 | // | |
909 | // | |
910 | let ln = self.live_node(expr.hir_id, expr.span); | |
911 | self.init_empty(ln, succ); | |
0bf4aa26 XL |
912 | for arm in arms { |
913 | let body_succ = self.propagate_through_expr(&arm.body, succ); | |
914 | ||
fc512014 XL |
915 | let guard_succ = arm.guard.as_ref().map_or(body_succ, |g| match g { |
916 | hir::Guard::If(e) => self.propagate_through_expr(e, body_succ), | |
917 | hir::Guard::IfLet(pat, e) => { | |
918 | let let_bind = self.define_bindings_in_pat(pat, body_succ); | |
919 | self.propagate_through_expr(e, let_bind) | |
920 | } | |
921 | }); | |
e74abb32 | 922 | let arm_succ = self.define_bindings_in_pat(&arm.pat, guard_succ); |
fc512014 | 923 | self.merge_from_succ(ln, arm_succ); |
dfeec247 | 924 | } |
0bf4aa26 XL |
925 | self.propagate_through_expr(&e, ln) |
926 | } | |
223e47cc | 927 | |
0bf4aa26 | 928 | hir::ExprKind::Ret(ref o_e) => { |
1b1a35ee XL |
929 | // Ignore succ and subst exit_ln. |
930 | self.propagate_through_opt_expr(o_e.as_ref().map(|e| &**e), self.exit_ln) | |
0bf4aa26 | 931 | } |
223e47cc | 932 | |
0bf4aa26 XL |
933 | hir::ExprKind::Break(label, ref opt_expr) => { |
934 | // Find which label this break jumps to | |
935 | let target = match label.target_id { | |
532ac7d7 | 936 | Ok(hir_id) => self.break_ln.get(&hir_id), |
94b46f34 | 937 | Err(err) => span_bug!(expr.span, "loop scope error: {}", err), |
dfeec247 XL |
938 | } |
939 | .cloned(); | |
223e47cc | 940 | |
0bf4aa26 XL |
941 | // Now that we know the label we're going to, |
942 | // look it up in the break loop nodes table | |
8bb4bdeb | 943 | |
0bf4aa26 XL |
944 | match target { |
945 | Some(b) => self.propagate_through_opt_expr(opt_expr.as_ref().map(|e| &**e), b), | |
f035d41b | 946 | None => span_bug!(expr.span, "`break` to unknown label"), |
0bf4aa26 XL |
947 | } |
948 | } | |
223e47cc | 949 | |
0bf4aa26 XL |
950 | hir::ExprKind::Continue(label) => { |
951 | // Find which label this expr continues to | |
dfeec247 XL |
952 | let sc = label |
953 | .target_id | |
954 | .unwrap_or_else(|err| span_bug!(expr.span, "loop scope error: {}", err)); | |
223e47cc | 955 | |
0bf4aa26 XL |
956 | // Now that we know the label we're going to, |
957 | // look it up in the continue loop nodes table | |
dfeec247 XL |
958 | self.cont_ln |
959 | .get(&sc) | |
960 | .cloned() | |
961 | .unwrap_or_else(|| span_bug!(expr.span, "continue to unknown label")) | |
0bf4aa26 | 962 | } |
223e47cc | 963 | |
dfeec247 | 964 | hir::ExprKind::Assign(ref l, ref r, _) => { |
2c00a5a8 XL |
965 | // see comment on places in |
966 | // propagate_through_place_components() | |
0bf4aa26 XL |
967 | let succ = self.write_place(&l, succ, ACC_WRITE); |
968 | let succ = self.propagate_through_place_components(&l, succ); | |
969 | self.propagate_through_expr(&r, succ) | |
54a0048b | 970 | } |
223e47cc | 971 | |
0bf4aa26 XL |
972 | hir::ExprKind::AssignOp(_, ref l, ref r) => { |
973 | // an overloaded assign op is like a method call | |
3dfed10e | 974 | if self.typeck_results.is_method_call(expr) { |
0bf4aa26 XL |
975 | let succ = self.propagate_through_expr(&l, succ); |
976 | self.propagate_through_expr(&r, succ) | |
977 | } else { | |
978 | // see comment on places in | |
979 | // propagate_through_place_components() | |
dfeec247 | 980 | let succ = self.write_place(&l, succ, ACC_WRITE | ACC_READ); |
0bf4aa26 XL |
981 | let succ = self.propagate_through_expr(&r, succ); |
982 | self.propagate_through_place_components(&l, succ) | |
983 | } | |
984 | } | |
223e47cc | 985 | |
0bf4aa26 | 986 | // Uninteresting cases: just propagate in rev exec order |
dfeec247 | 987 | hir::ExprKind::Array(ref exprs) => self.propagate_through_exprs(exprs, succ), |
223e47cc | 988 | |
0bf4aa26 XL |
989 | hir::ExprKind::Struct(_, ref fields, ref with_expr) => { |
990 | let succ = self.propagate_through_opt_expr(with_expr.as_ref().map(|e| &**e), succ); | |
dfeec247 XL |
991 | fields |
992 | .iter() | |
993 | .rev() | |
994 | .fold(succ, |succ, field| self.propagate_through_expr(&field.expr, succ)) | |
0bf4aa26 | 995 | } |
223e47cc | 996 | |
0bf4aa26 | 997 | hir::ExprKind::Call(ref f, ref args) => { |
94222f64 | 998 | let succ = self.check_is_ty_uninhabited(expr, succ); |
0bf4aa26 XL |
999 | let succ = self.propagate_through_exprs(args, succ); |
1000 | self.propagate_through_expr(&f, succ) | |
1001 | } | |
223e47cc | 1002 | |
f035d41b | 1003 | hir::ExprKind::MethodCall(.., ref args, _) => { |
94222f64 | 1004 | let succ = self.check_is_ty_uninhabited(expr, succ); |
0bf4aa26 XL |
1005 | self.propagate_through_exprs(args, succ) |
1006 | } | |
223e47cc | 1007 | |
dfeec247 | 1008 | hir::ExprKind::Tup(ref exprs) => self.propagate_through_exprs(exprs, succ), |
223e47cc | 1009 | |
0bf4aa26 XL |
1010 | hir::ExprKind::Binary(op, ref l, ref r) if op.node.is_lazy() => { |
1011 | let r_succ = self.propagate_through_expr(&r, succ); | |
223e47cc | 1012 | |
0bf4aa26 XL |
1013 | let ln = self.live_node(expr.hir_id, expr.span); |
1014 | self.init_from_succ(ln, succ); | |
fc512014 | 1015 | self.merge_from_succ(ln, r_succ); |
223e47cc | 1016 | |
0bf4aa26 XL |
1017 | self.propagate_through_expr(&l, ln) |
1018 | } | |
1a4d82fc | 1019 | |
dfeec247 | 1020 | hir::ExprKind::Index(ref l, ref r) | hir::ExprKind::Binary(_, ref l, ref r) => { |
0bf4aa26 XL |
1021 | let r_succ = self.propagate_through_expr(&r, succ); |
1022 | self.propagate_through_expr(&l, r_succ) | |
1023 | } | |
1024 | ||
dfeec247 XL |
1025 | hir::ExprKind::Box(ref e) |
1026 | | hir::ExprKind::AddrOf(_, _, ref e) | |
1027 | | hir::ExprKind::Cast(ref e, _) | |
1028 | | hir::ExprKind::Type(ref e, _) | |
1029 | | hir::ExprKind::DropTemps(ref e) | |
1030 | | hir::ExprKind::Unary(_, ref e) | |
dfeec247 | 1031 | | hir::ExprKind::Repeat(ref e, _) => self.propagate_through_expr(&e, succ), |
0bf4aa26 | 1032 | |
f9f354fc XL |
1033 | hir::ExprKind::InlineAsm(ref asm) => { |
1034 | // Handle non-returning asm | |
1035 | let mut succ = if asm.options.contains(InlineAsmOptions::NORETURN) { | |
1b1a35ee | 1036 | self.exit_ln |
f9f354fc XL |
1037 | } else { |
1038 | succ | |
1039 | }; | |
1040 | ||
1041 | // Do a first pass for writing outputs only | |
fc512014 | 1042 | for (op, _op_sp) in asm.operands.iter().rev() { |
f9f354fc XL |
1043 | match op { |
1044 | hir::InlineAsmOperand::In { .. } | |
1045 | | hir::InlineAsmOperand::Const { .. } | |
1046 | | hir::InlineAsmOperand::Sym { .. } => {} | |
1047 | hir::InlineAsmOperand::Out { expr, .. } => { | |
1048 | if let Some(expr) = expr { | |
1049 | succ = self.write_place(expr, succ, ACC_WRITE); | |
1050 | } | |
1051 | } | |
1052 | hir::InlineAsmOperand::InOut { expr, .. } => { | |
29967ef6 | 1053 | succ = self.write_place(expr, succ, ACC_READ | ACC_WRITE | ACC_USE); |
f9f354fc XL |
1054 | } |
1055 | hir::InlineAsmOperand::SplitInOut { out_expr, .. } => { | |
1056 | if let Some(expr) = out_expr { | |
1057 | succ = self.write_place(expr, succ, ACC_WRITE); | |
1058 | } | |
1059 | } | |
1060 | } | |
1061 | } | |
1062 | ||
1063 | // Then do a second pass for inputs | |
1064 | let mut succ = succ; | |
fc512014 | 1065 | for (op, _op_sp) in asm.operands.iter().rev() { |
f9f354fc XL |
1066 | match op { |
1067 | hir::InlineAsmOperand::In { expr, .. } | |
f9f354fc XL |
1068 | | hir::InlineAsmOperand::Sym { expr, .. } => { |
1069 | succ = self.propagate_through_expr(expr, succ) | |
1070 | } | |
1071 | hir::InlineAsmOperand::Out { expr, .. } => { | |
1072 | if let Some(expr) = expr { | |
1073 | succ = self.propagate_through_place_components(expr, succ); | |
1074 | } | |
1075 | } | |
1076 | hir::InlineAsmOperand::InOut { expr, .. } => { | |
1077 | succ = self.propagate_through_place_components(expr, succ); | |
1078 | } | |
1079 | hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => { | |
1080 | if let Some(expr) = out_expr { | |
1081 | succ = self.propagate_through_place_components(expr, succ); | |
1082 | } | |
1083 | succ = self.propagate_through_expr(in_expr, succ); | |
1084 | } | |
cdc7bbd5 | 1085 | hir::InlineAsmOperand::Const { .. } => {} |
f9f354fc XL |
1086 | } |
1087 | } | |
1088 | succ | |
1089 | } | |
1090 | ||
dfeec247 | 1091 | hir::ExprKind::Lit(..) |
29967ef6 | 1092 | | hir::ExprKind::ConstBlock(..) |
dfeec247 | 1093 | | hir::ExprKind::Err |
3dfed10e XL |
1094 | | hir::ExprKind::Path(hir::QPath::TypeRelative(..)) |
1095 | | hir::ExprKind::Path(hir::QPath::LangItem(..)) => succ, | |
223e47cc | 1096 | |
0bf4aa26 XL |
1097 | // Note that labels have been resolved, so we don't need to look |
1098 | // at the label ident | |
dfeec247 | 1099 | hir::ExprKind::Block(ref blk, _) => self.propagate_through_block(&blk, succ), |
223e47cc LB |
1100 | } |
1101 | } | |
1102 | ||
dfeec247 | 1103 | fn propagate_through_place_components(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode { |
2c00a5a8 | 1104 | // # Places |
223e47cc LB |
1105 | // |
1106 | // In general, the full flow graph structure for an | |
1107 | // assignment/move/etc can be handled in one of two ways, | |
1108 | // depending on whether what is being assigned is a "tracked | |
1109 | // value" or not. A tracked value is basically a local | |
1110 | // variable or argument. | |
1111 | // | |
1112 | // The two kinds of graphs are: | |
1113 | // | |
2c00a5a8 | 1114 | // Tracked place Untracked place |
223e47cc LB |
1115 | // ----------------------++----------------------- |
1116 | // || | |
1117 | // | || | | |
1118 | // v || v | |
1119 | // (rvalue) || (rvalue) | |
1120 | // | || | | |
1121 | // v || v | |
2c00a5a8 | 1122 | // (write of place) || (place components) |
223e47cc LB |
1123 | // | || | |
1124 | // v || v | |
1125 | // (succ) || (succ) | |
1126 | // || | |
1127 | // ----------------------++----------------------- | |
1128 | // | |
1129 | // I will cover the two cases in turn: | |
1130 | // | |
2c00a5a8 | 1131 | // # Tracked places |
223e47cc | 1132 | // |
2c00a5a8 | 1133 | // A tracked place is a local variable/argument `x`. In |
223e47cc | 1134 | // these cases, the link_node where the write occurs is linked |
2c00a5a8 | 1135 | // to node id of `x`. The `write_place()` routine generates |
223e47cc LB |
1136 | // the contents of this node. There are no subcomponents to |
1137 | // consider. | |
1138 | // | |
2c00a5a8 | 1139 | // # Non-tracked places |
223e47cc | 1140 | // |
2c00a5a8 | 1141 | // These are places like `x[5]` or `x.f`. In that case, we |
223e47cc LB |
1142 | // basically ignore the value which is written to but generate |
1143 | // reads for the components---`x` in these two examples. The | |
1144 | // components reads are generated by | |
2c00a5a8 | 1145 | // `propagate_through_place_components()` (this fn). |
223e47cc | 1146 | // |
2c00a5a8 | 1147 | // # Illegal places |
223e47cc | 1148 | // |
2c00a5a8 | 1149 | // It is still possible to observe assignments to non-places; |
223e47cc LB |
1150 | // these errors are detected in the later pass borrowck. We |
1151 | // just ignore such cases and treat them as reads. | |
1152 | ||
e74abb32 | 1153 | match expr.kind { |
8faf50e0 XL |
1154 | hir::ExprKind::Path(_) => succ, |
1155 | hir::ExprKind::Field(ref e, _) => self.propagate_through_expr(&e, succ), | |
dfeec247 | 1156 | _ => self.propagate_through_expr(expr, succ), |
223e47cc LB |
1157 | } |
1158 | } | |
1159 | ||
2c00a5a8 | 1160 | // see comment on propagate_through_place() |
dfeec247 | 1161 | fn write_place(&mut self, expr: &Expr<'_>, succ: LiveNode, acc: u32) -> LiveNode { |
e74abb32 | 1162 | match expr.kind { |
0bf4aa26 XL |
1163 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { |
1164 | self.access_path(expr.hir_id, path, succ, acc) | |
1165 | } | |
223e47cc | 1166 | |
0bf4aa26 XL |
1167 | // We do not track other places, so just propagate through |
1168 | // to their subcomponents. Also, it may happen that | |
1169 | // non-places occur here, because those are detected in the | |
1170 | // later pass borrowck. | |
dfeec247 | 1171 | _ => succ, |
223e47cc LB |
1172 | } |
1173 | } | |
1174 | ||
dfeec247 XL |
1175 | fn access_var( |
1176 | &mut self, | |
1177 | hir_id: HirId, | |
1178 | var_hid: HirId, | |
1179 | succ: LiveNode, | |
1180 | acc: u32, | |
1181 | span: Span, | |
1182 | ) -> LiveNode { | |
94b46f34 | 1183 | let ln = self.live_node(hir_id, span); |
ea8adc8c XL |
1184 | if acc != 0 { |
1185 | self.init_from_succ(ln, succ); | |
94b46f34 | 1186 | let var = self.variable(var_hid, span); |
ea8adc8c XL |
1187 | self.acc(ln, var, acc); |
1188 | } | |
1189 | ln | |
1190 | } | |
1191 | ||
dfeec247 XL |
1192 | fn access_path( |
1193 | &mut self, | |
1194 | hir_id: HirId, | |
1195 | path: &hir::Path<'_>, | |
1196 | succ: LiveNode, | |
1197 | acc: u32, | |
1198 | ) -> LiveNode { | |
48663c56 | 1199 | match path.res { |
94222f64 | 1200 | Res::Local(hid) => self.access_var(hir_id, hid, succ, acc, path.span), |
dfeec247 | 1201 | _ => succ, |
223e47cc LB |
1202 | } |
1203 | } | |
1204 | ||
416331ca XL |
1205 | fn propagate_through_loop( |
1206 | &mut self, | |
dfeec247 XL |
1207 | expr: &Expr<'_>, |
1208 | body: &hir::Block<'_>, | |
1209 | succ: LiveNode, | |
416331ca | 1210 | ) -> LiveNode { |
223e47cc | 1211 | /* |
223e47cc LB |
1212 | We model control flow like this: |
1213 | ||
416331ca XL |
1214 | (expr) <-+ |
1215 | | | | |
1216 | v | | |
1217 | (body) --+ | |
223e47cc | 1218 | |
416331ca XL |
1219 | Note that a `continue` expression targeting the `loop` will have a successor of `expr`. |
1220 | Meanwhile, a `break` expression will have a successor of `succ`. | |
223e47cc LB |
1221 | */ |
1222 | ||
223e47cc | 1223 | // first iteration: |
94b46f34 | 1224 | let ln = self.live_node(expr.hir_id, expr.span); |
223e47cc | 1225 | self.init_empty(ln, succ); |
ba9703b0 | 1226 | debug!("propagate_through_loop: using id for loop body {} {:?}", expr.hir_id, body); |
9fa01778 | 1227 | |
532ac7d7 | 1228 | self.break_ln.insert(expr.hir_id, succ); |
cc61c64b | 1229 | |
416331ca | 1230 | self.cont_ln.insert(expr.hir_id, ln); |
9fa01778 | 1231 | |
416331ca | 1232 | let body_ln = self.propagate_through_block(body, ln); |
223e47cc LB |
1233 | |
1234 | // repeat until fixed point is reached: | |
fc512014 | 1235 | while self.merge_from_succ(ln, body_ln) { |
416331ca | 1236 | assert_eq!(body_ln, self.propagate_through_block(body, ln)); |
223e47cc LB |
1237 | } |
1238 | ||
416331ca | 1239 | ln |
223e47cc | 1240 | } |
94222f64 XL |
1241 | |
1242 | fn check_is_ty_uninhabited(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode { | |
1243 | let ty = self.typeck_results.expr_ty(expr); | |
1244 | let m = self.ir.tcx.parent_module(expr.hir_id).to_def_id(); | |
1245 | if self.ir.tcx.is_ty_uninhabited_from(m, ty, self.param_env) { | |
1246 | match self.ir.lnks[succ] { | |
1247 | LiveNodeKind::ExprNode(succ_span, succ_id) => { | |
1248 | self.warn_about_unreachable(expr.span, ty, succ_span, succ_id, "expression"); | |
1249 | } | |
1250 | LiveNodeKind::VarDefNode(succ_span, succ_id) => { | |
1251 | self.warn_about_unreachable(expr.span, ty, succ_span, succ_id, "definition"); | |
1252 | } | |
1253 | _ => {} | |
1254 | }; | |
1255 | self.exit_ln | |
1256 | } else { | |
1257 | succ | |
1258 | } | |
1259 | } | |
1260 | ||
1261 | fn warn_about_unreachable( | |
1262 | &mut self, | |
1263 | orig_span: Span, | |
1264 | orig_ty: Ty<'tcx>, | |
1265 | expr_span: Span, | |
1266 | expr_id: HirId, | |
1267 | descr: &str, | |
1268 | ) { | |
1269 | if !orig_ty.is_never() { | |
1270 | // Unreachable code warnings are already emitted during type checking. | |
1271 | // However, during type checking, full type information is being | |
1272 | // calculated but not yet available, so the check for diverging | |
1273 | // expressions due to uninhabited result types is pretty crude and | |
1274 | // only checks whether ty.is_never(). Here, we have full type | |
1275 | // information available and can issue warnings for less obviously | |
1276 | // uninhabited types (e.g. empty enums). The check above is used so | |
1277 | // that we do not emit the same warning twice if the uninhabited type | |
1278 | // is indeed `!`. | |
1279 | ||
1280 | self.ir.tcx.struct_span_lint_hir( | |
1281 | lint::builtin::UNREACHABLE_CODE, | |
1282 | expr_id, | |
1283 | expr_span, | |
1284 | |lint| { | |
1285 | let msg = format!("unreachable {}", descr); | |
1286 | lint.build(&msg) | |
1287 | .span_label(expr_span, &msg) | |
1288 | .span_label(orig_span, "any code following this expression is unreachable") | |
1289 | .span_note( | |
1290 | orig_span, | |
1291 | &format!( | |
1292 | "this expression has type `{}`, which is uninhabited", | |
1293 | orig_ty | |
1294 | ), | |
1295 | ) | |
1296 | .emit(); | |
1297 | }, | |
1298 | ); | |
1299 | } | |
1300 | } | |
223e47cc LB |
1301 | } |
1302 | ||
1303 | // _______________________________________________________________________ | |
1304 | // Checking for error conditions | |
1305 | ||
32a655c1 | 1306 | impl<'a, 'tcx> Visitor<'tcx> for Liveness<'a, 'tcx> { |
dfeec247 | 1307 | fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) { |
e74abb32 XL |
1308 | self.check_unused_vars_in_pat(&local.pat, None, |spans, hir_id, ln, var| { |
1309 | if local.init.is_some() { | |
1310 | self.warn_about_dead_assign(spans, hir_id, ln, var); | |
1311 | } | |
1312 | }); | |
32a655c1 | 1313 | |
e74abb32 | 1314 | intravisit::walk_local(self, local); |
223e47cc LB |
1315 | } |
1316 | ||
dfeec247 | 1317 | fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) { |
e74abb32 | 1318 | check_expr(self, ex); |
94222f64 | 1319 | intravisit::walk_expr(self, ex); |
9fa01778 XL |
1320 | } |
1321 | ||
dfeec247 | 1322 | fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) { |
e74abb32 XL |
1323 | self.check_unused_vars_in_pat(&arm.pat, None, |_, _, _, _| {}); |
1324 | intravisit::walk_arm(self, arm); | |
9fa01778 | 1325 | } |
223e47cc LB |
1326 | } |
1327 | ||
dfeec247 | 1328 | fn check_expr<'tcx>(this: &mut Liveness<'_, 'tcx>, expr: &'tcx Expr<'tcx>) { |
e74abb32 | 1329 | match expr.kind { |
dfeec247 | 1330 | hir::ExprKind::Assign(ref l, ..) => { |
2c00a5a8 | 1331 | this.check_place(&l); |
54a0048b | 1332 | } |
223e47cc | 1333 | |
0bf4aa26 | 1334 | hir::ExprKind::AssignOp(_, ref l, _) => { |
3dfed10e | 1335 | if !this.typeck_results.is_method_call(expr) { |
0bf4aa26 XL |
1336 | this.check_place(&l); |
1337 | } | |
223e47cc LB |
1338 | } |
1339 | ||
f9f354fc | 1340 | hir::ExprKind::InlineAsm(ref asm) => { |
fc512014 | 1341 | for (op, _op_sp) in asm.operands { |
f9f354fc XL |
1342 | match op { |
1343 | hir::InlineAsmOperand::Out { expr, .. } => { | |
1344 | if let Some(expr) = expr { | |
1345 | this.check_place(expr); | |
1346 | } | |
1347 | } | |
1348 | hir::InlineAsmOperand::InOut { expr, .. } => { | |
1349 | this.check_place(expr); | |
1350 | } | |
1351 | hir::InlineAsmOperand::SplitInOut { out_expr, .. } => { | |
1352 | if let Some(out_expr) = out_expr { | |
1353 | this.check_place(out_expr); | |
1354 | } | |
1355 | } | |
1356 | _ => {} | |
1357 | } | |
1358 | } | |
1359 | } | |
1360 | ||
a2a8927a XL |
1361 | hir::ExprKind::Let(let_expr) => { |
1362 | this.check_unused_vars_in_pat(let_expr.pat, None, |_, _, _, _| {}); | |
94222f64 XL |
1363 | } |
1364 | ||
0bf4aa26 | 1365 | // no correctness conditions related to liveness |
dfeec247 XL |
1366 | hir::ExprKind::Call(..) |
1367 | | hir::ExprKind::MethodCall(..) | |
1368 | | hir::ExprKind::Match(..) | |
1369 | | hir::ExprKind::Loop(..) | |
1370 | | hir::ExprKind::Index(..) | |
1371 | | hir::ExprKind::Field(..) | |
1372 | | hir::ExprKind::Array(..) | |
1373 | | hir::ExprKind::Tup(..) | |
1374 | | hir::ExprKind::Binary(..) | |
1375 | | hir::ExprKind::Cast(..) | |
5869c6ff | 1376 | | hir::ExprKind::If(..) |
dfeec247 XL |
1377 | | hir::ExprKind::DropTemps(..) |
1378 | | hir::ExprKind::Unary(..) | |
1379 | | hir::ExprKind::Ret(..) | |
1380 | | hir::ExprKind::Break(..) | |
1381 | | hir::ExprKind::Continue(..) | |
1382 | | hir::ExprKind::Lit(_) | |
29967ef6 | 1383 | | hir::ExprKind::ConstBlock(..) |
dfeec247 XL |
1384 | | hir::ExprKind::Block(..) |
1385 | | hir::ExprKind::AddrOf(..) | |
1386 | | hir::ExprKind::Struct(..) | |
1387 | | hir::ExprKind::Repeat(..) | |
1388 | | hir::ExprKind::Closure(..) | |
1389 | | hir::ExprKind::Path(_) | |
1390 | | hir::ExprKind::Yield(..) | |
1391 | | hir::ExprKind::Box(..) | |
1392 | | hir::ExprKind::Type(..) | |
1393 | | hir::ExprKind::Err => {} | |
223e47cc LB |
1394 | } |
1395 | } | |
1396 | ||
e74abb32 | 1397 | impl<'tcx> Liveness<'_, 'tcx> { |
dfeec247 | 1398 | fn check_place(&mut self, expr: &'tcx Expr<'tcx>) { |
e74abb32 | 1399 | match expr.kind { |
8faf50e0 | 1400 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { |
48663c56 | 1401 | if let Res::Local(var_hid) = path.res { |
f9f354fc XL |
1402 | // Assignment to an immutable variable or argument: only legal |
1403 | // if there is no later assignment. If this local is actually | |
1404 | // mutable, then check for a reassignment to flag the mutability | |
1405 | // as being used. | |
1406 | let ln = self.live_node(expr.hir_id, expr.span); | |
1407 | let var = self.variable(var_hid, expr.span); | |
1408 | self.warn_about_dead_assign(vec![expr.span], expr.hir_id, ln, var); | |
223e47cc | 1409 | } |
223e47cc | 1410 | } |
1a4d82fc | 1411 | _ => { |
2c00a5a8 | 1412 | // For other kinds of places, no checks are required, |
1a4d82fc | 1413 | // and any embedded expressions are actually rvalues |
92a42be0 | 1414 | intravisit::walk_expr(self, expr); |
1a4d82fc | 1415 | } |
223e47cc LB |
1416 | } |
1417 | } | |
1418 | ||
1a4d82fc | 1419 | fn should_warn(&self, var: Variable) -> Option<String> { |
223e47cc | 1420 | let name = self.ir.variable_name(var); |
5869c6ff | 1421 | if name == kw::Empty { |
1b1a35ee XL |
1422 | return None; |
1423 | } | |
a2a8927a | 1424 | let name = name.as_str(); |
1b1a35ee XL |
1425 | if name.as_bytes()[0] == b'_' { |
1426 | return None; | |
1427 | } | |
1428 | Some(name.to_owned()) | |
223e47cc LB |
1429 | } |
1430 | ||
f9f354fc | 1431 | fn warn_about_unused_upvars(&self, entry_ln: LiveNode) { |
5e7ed085 FG |
1432 | let Some(closure_min_captures) = self.closure_min_captures else { |
1433 | return; | |
f9f354fc | 1434 | }; |
fc512014 | 1435 | |
6a06907d XL |
1436 | // If closure_min_captures is Some(), upvars must be Some() too. |
1437 | for (&var_hir_id, min_capture_list) in closure_min_captures { | |
1438 | for captured_place in min_capture_list { | |
1439 | match captured_place.info.capture_kind { | |
5099ac24 | 1440 | ty::UpvarCapture::ByValue => {} |
6a06907d XL |
1441 | ty::UpvarCapture::ByRef(..) => continue, |
1442 | }; | |
1443 | let span = captured_place.get_capture_kind_span(self.ir.tcx); | |
1444 | let var = self.variable(var_hir_id, span); | |
1445 | if self.used_on_entry(entry_ln, var) { | |
1446 | if !self.live_on_entry(entry_ln, var) { | |
1447 | if let Some(name) = self.should_warn(var) { | |
1448 | self.ir.tcx.struct_span_lint_hir( | |
1449 | lint::builtin::UNUSED_ASSIGNMENTS, | |
1450 | var_hir_id, | |
1451 | vec![span], | |
1452 | |lint| { | |
1453 | lint.build(&format!( | |
1454 | "value captured by `{}` is never read", | |
1455 | name | |
1456 | )) | |
1457 | .help("did you mean to capture by reference instead?") | |
1458 | .emit(); | |
1459 | }, | |
1460 | ); | |
1461 | } | |
1462 | } | |
1463 | } else { | |
f9f354fc XL |
1464 | if let Some(name) = self.should_warn(var) { |
1465 | self.ir.tcx.struct_span_lint_hir( | |
6a06907d | 1466 | lint::builtin::UNUSED_VARIABLES, |
f9f354fc | 1467 | var_hir_id, |
6a06907d | 1468 | vec![span], |
f9f354fc | 1469 | |lint| { |
6a06907d | 1470 | lint.build(&format!("unused variable: `{}`", name)) |
f9f354fc XL |
1471 | .help("did you mean to capture by reference instead?") |
1472 | .emit(); | |
1473 | }, | |
1474 | ); | |
1475 | } | |
1476 | } | |
f9f354fc XL |
1477 | } |
1478 | } | |
1479 | } | |
1480 | ||
dfeec247 XL |
1481 | fn warn_about_unused_args(&self, body: &hir::Body<'_>, entry_ln: LiveNode) { |
1482 | for p in body.params { | |
e74abb32 | 1483 | self.check_unused_vars_in_pat(&p.pat, Some(entry_ln), |spans, hir_id, ln, var| { |
fc512014 | 1484 | if !self.live_on_entry(ln, var) { |
cdc7bbd5 | 1485 | self.report_unused_assign(hir_id, spans, var, |name| { |
f9f354fc XL |
1486 | format!("value passed to `{}` is never read", name) |
1487 | }); | |
1a4d82fc | 1488 | } |
e74abb32 | 1489 | }); |
223e47cc LB |
1490 | } |
1491 | } | |
1492 | ||
e74abb32 XL |
1493 | fn check_unused_vars_in_pat( |
1494 | &self, | |
dfeec247 | 1495 | pat: &hir::Pat<'_>, |
e74abb32 XL |
1496 | entry_ln: Option<LiveNode>, |
1497 | on_used_on_entry: impl Fn(Vec<Span>, HirId, LiveNode, Variable), | |
1498 | ) { | |
1499 | // In an or-pattern, only consider the variable; any later patterns must have the same | |
1500 | // bindings, and we also consider the first pattern to be the "authoritative" set of ids. | |
ba9703b0 | 1501 | // However, we should take the ids and spans of variables with the same name from the later |
e74abb32 | 1502 | // patterns so the suggestions to prefix with underscores will apply to those too. |
6a06907d XL |
1503 | let mut vars: FxIndexMap<Symbol, (LiveNode, Variable, Vec<(HirId, Span, Span)>)> = |
1504 | <_>::default(); | |
e74abb32 XL |
1505 | |
1506 | pat.each_binding(|_, hir_id, pat_sp, ident| { | |
1507 | let ln = entry_ln.unwrap_or_else(|| self.live_node(hir_id, pat_sp)); | |
1508 | let var = self.variable(hir_id, ident.span); | |
6a06907d | 1509 | let id_and_sp = (hir_id, pat_sp, ident.span); |
e74abb32 | 1510 | vars.entry(self.ir.variable_name(var)) |
ba9703b0 XL |
1511 | .and_modify(|(.., hir_ids_and_spans)| hir_ids_and_spans.push(id_and_sp)) |
1512 | .or_insert_with(|| (ln, var, vec![id_and_sp])); | |
e74abb32 XL |
1513 | }); |
1514 | ||
ba9703b0 | 1515 | for (_, (ln, var, hir_ids_and_spans)) in vars { |
e74abb32 | 1516 | if self.used_on_entry(ln, var) { |
ba9703b0 | 1517 | let id = hir_ids_and_spans[0].0; |
6a06907d XL |
1518 | let spans = |
1519 | hir_ids_and_spans.into_iter().map(|(_, _, ident_span)| ident_span).collect(); | |
e74abb32 XL |
1520 | on_used_on_entry(spans, id, ln, var); |
1521 | } else { | |
ba9703b0 | 1522 | self.report_unused(hir_ids_and_spans, ln, var); |
223e47cc | 1523 | } |
e74abb32 | 1524 | } |
223e47cc LB |
1525 | } |
1526 | ||
6a06907d XL |
1527 | fn report_unused( |
1528 | &self, | |
1529 | hir_ids_and_spans: Vec<(HirId, Span, Span)>, | |
1530 | ln: LiveNode, | |
1531 | var: Variable, | |
1532 | ) { | |
ba9703b0 XL |
1533 | let first_hir_id = hir_ids_and_spans[0].0; |
1534 | ||
e74abb32 XL |
1535 | if let Some(name) = self.should_warn(var).filter(|name| name != "self") { |
1536 | // annoying: for parameters in funcs like `fn(x: i32) | |
1537 | // {ret}`, there is only one node, so asking about | |
1538 | // assigned_on_exit() is not meaningful. | |
dfeec247 | 1539 | let is_assigned = |
fc512014 | 1540 | if ln == self.exit_ln { false } else { self.assigned_on_exit(ln, var) }; |
223e47cc | 1541 | |
e74abb32 | 1542 | if is_assigned { |
74b04a01 XL |
1543 | self.ir.tcx.struct_span_lint_hir( |
1544 | lint::builtin::UNUSED_VARIABLES, | |
ba9703b0 | 1545 | first_hir_id, |
6a06907d XL |
1546 | hir_ids_and_spans |
1547 | .into_iter() | |
1548 | .map(|(_, _, ident_span)| ident_span) | |
1549 | .collect::<Vec<_>>(), | |
74b04a01 XL |
1550 | |lint| { |
1551 | lint.build(&format!("variable `{}` is assigned to, but never used", name)) | |
1552 | .note(&format!("consider using `_{}` instead", name)) | |
1553 | .emit(); | |
1554 | }, | |
1555 | ) | |
e74abb32 | 1556 | } else { |
6a06907d XL |
1557 | let (shorthands, non_shorthands): (Vec<_>, Vec<_>) = |
1558 | hir_ids_and_spans.iter().copied().partition(|(hir_id, _, ident_span)| { | |
1559 | let var = self.variable(*hir_id, *ident_span); | |
1560 | self.ir.variable_is_shorthand(var) | |
1561 | }); | |
ba9703b0 | 1562 | |
6a06907d XL |
1563 | // If we have both shorthand and non-shorthand, prefer the "try ignoring |
1564 | // the field" message, and suggest `_` for the non-shorthands. If we only | |
1565 | // have non-shorthand, then prefix with an underscore instead. | |
1566 | if !shorthands.is_empty() { | |
1567 | let shorthands = shorthands | |
1568 | .into_iter() | |
1569 | .map(|(_, pat_span, _)| (pat_span, format!("{}: _", name))) | |
1570 | .chain( | |
1571 | non_shorthands | |
1572 | .into_iter() | |
1573 | .map(|(_, pat_span, _)| (pat_span, "_".to_string())), | |
1574 | ) | |
1575 | .collect::<Vec<_>>(); | |
1576 | ||
1577 | self.ir.tcx.struct_span_lint_hir( | |
1578 | lint::builtin::UNUSED_VARIABLES, | |
1579 | first_hir_id, | |
1580 | hir_ids_and_spans | |
1581 | .iter() | |
1582 | .map(|(_, pat_span, _)| *pat_span) | |
1583 | .collect::<Vec<_>>(), | |
1584 | |lint| { | |
1585 | let mut err = lint.build(&format!("unused variable: `{}`", name)); | |
ba9703b0 XL |
1586 | err.multipart_suggestion( |
1587 | "try ignoring the field", | |
1588 | shorthands, | |
1589 | Applicability::MachineApplicable, | |
1590 | ); | |
5e7ed085 | 1591 | err.emit(); |
6a06907d XL |
1592 | }, |
1593 | ); | |
1594 | } else { | |
1595 | let non_shorthands = non_shorthands | |
1596 | .into_iter() | |
1597 | .map(|(_, _, ident_span)| (ident_span, format!("_{}", name))) | |
1598 | .collect::<Vec<_>>(); | |
1599 | ||
1600 | self.ir.tcx.struct_span_lint_hir( | |
1601 | lint::builtin::UNUSED_VARIABLES, | |
1602 | first_hir_id, | |
1603 | hir_ids_and_spans | |
1604 | .iter() | |
1605 | .map(|(_, _, ident_span)| *ident_span) | |
1606 | .collect::<Vec<_>>(), | |
1607 | |lint| { | |
1608 | let mut err = lint.build(&format!("unused variable: `{}`", name)); | |
74b04a01 | 1609 | err.multipart_suggestion( |
ba9703b0 | 1610 | "if this is intentional, prefix it with an underscore", |
6a06907d | 1611 | non_shorthands, |
74b04a01 XL |
1612 | Applicability::MachineApplicable, |
1613 | ); | |
5e7ed085 | 1614 | err.emit(); |
6a06907d XL |
1615 | }, |
1616 | ); | |
1617 | } | |
223e47cc | 1618 | } |
223e47cc | 1619 | } |
223e47cc LB |
1620 | } |
1621 | ||
e74abb32 | 1622 | fn warn_about_dead_assign(&self, spans: Vec<Span>, hir_id: HirId, ln: LiveNode, var: Variable) { |
fc512014 | 1623 | if !self.live_on_exit(ln, var) { |
cdc7bbd5 | 1624 | self.report_unused_assign(hir_id, spans, var, |name| { |
f9f354fc XL |
1625 | format!("value assigned to `{}` is never read", name) |
1626 | }); | |
92a42be0 SL |
1627 | } |
1628 | } | |
1629 | ||
cdc7bbd5 | 1630 | fn report_unused_assign( |
f9f354fc XL |
1631 | &self, |
1632 | hir_id: HirId, | |
1633 | spans: Vec<Span>, | |
1634 | var: Variable, | |
1635 | message: impl Fn(&str) -> String, | |
1636 | ) { | |
92a42be0 | 1637 | if let Some(name) = self.should_warn(var) { |
f9f354fc XL |
1638 | self.ir.tcx.struct_span_lint_hir( |
1639 | lint::builtin::UNUSED_ASSIGNMENTS, | |
1640 | hir_id, | |
1641 | spans, | |
1642 | |lint| { | |
1643 | lint.build(&message(&name)) | |
1644 | .help("maybe it is overwritten before being read?") | |
1645 | .emit(); | |
1646 | }, | |
1647 | ) | |
223e47cc LB |
1648 | } |
1649 | } | |
92a42be0 | 1650 | } |