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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 | 89 | use rustc_errors::Applicability; |
6522a427 | 90 | use rustc_errors::Diagnostic; |
dfeec247 XL |
91 | use rustc_hir as hir; |
92 | use rustc_hir::def::*; | |
f2b60f7d | 93 | use rustc_hir::def_id::{DefId, LocalDefId}; |
5099ac24 | 94 | use rustc_hir::intravisit::{self, Visitor}; |
1b1a35ee XL |
95 | use rustc_hir::{Expr, HirId, HirIdMap, HirIdSet}; |
96 | use rustc_index::vec::IndexVec; | |
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}; |
f2b60f7d | 101 | use rustc_span::{BytePos, 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 | 110 | rustc_index::newtype_index! { |
6522a427 EL |
111 | #[debug_format = "v({})"] |
112 | pub struct Variable {} | |
1a4d82fc JJ |
113 | } |
114 | ||
1b1a35ee | 115 | rustc_index::newtype_index! { |
6522a427 EL |
116 | #[debug_format = "ln({})"] |
117 | pub struct LiveNode {} | |
1a4d82fc JJ |
118 | } |
119 | ||
c34b1796 | 120 | #[derive(Copy, Clone, PartialEq, Debug)] |
223e47cc | 121 | enum LiveNodeKind { |
48663c56 | 122 | UpvarNode(Span), |
94222f64 XL |
123 | ExprNode(Span, HirId), |
124 | VarDefNode(Span, HirId), | |
f9f354fc | 125 | ClosureNode, |
dfeec247 | 126 | ExitNode, |
223e47cc LB |
127 | } |
128 | ||
dc9dc135 | 129 | fn live_node_kind_to_string(lnk: LiveNodeKind, tcx: TyCtxt<'_>) -> String { |
74b04a01 | 130 | let sm = tcx.sess.source_map(); |
223e47cc | 131 | match lnk { |
17df50a5 | 132 | UpvarNode(s) => format!("Upvar node [{}]", sm.span_to_diagnostic_string(s)), |
94222f64 XL |
133 | ExprNode(s, _) => format!("Expr node [{}]", sm.span_to_diagnostic_string(s)), |
134 | VarDefNode(s, _) => format!("Var def node [{}]", sm.span_to_diagnostic_string(s)), | |
f9f354fc | 135 | ClosureNode => "Closure node".to_owned(), |
0bf4aa26 | 136 | ExitNode => "Exit node".to_owned(), |
223e47cc LB |
137 | } |
138 | } | |
139 | ||
f2b60f7d FG |
140 | fn check_liveness(tcx: TyCtxt<'_>, def_id: DefId) { |
141 | let local_def_id = match def_id.as_local() { | |
142 | None => return, | |
143 | Some(def_id) => def_id, | |
144 | }; | |
145 | ||
146 | // Don't run unused pass for #[derive()] | |
147 | let parent = tcx.local_parent(local_def_id); | |
148 | if let DefKind::Impl = tcx.def_kind(parent) | |
149 | && tcx.has_attr(parent.to_def_id(), sym::automatically_derived) | |
150 | { | |
151 | return; | |
152 | } | |
153 | ||
154 | // Don't run unused pass for #[naked] | |
155 | if tcx.has_attr(def_id, sym::naked) { | |
156 | return; | |
157 | } | |
158 | ||
159 | let mut maps = IrMaps::new(tcx); | |
160 | let body_id = tcx.hir().body_owned_by(local_def_id); | |
161 | let hir_id = tcx.hir().body_owner(body_id); | |
162 | let body = tcx.hir().body(body_id); | |
163 | ||
164 | if let Some(upvars) = tcx.upvars_mentioned(def_id) { | |
165 | for &var_hir_id in upvars.keys() { | |
166 | let var_name = tcx.hir().name(var_hir_id); | |
167 | maps.add_variable(Upvar(var_hir_id, var_name)); | |
168 | } | |
169 | } | |
170 | ||
171 | // gather up the various local variables, significant expressions, | |
172 | // and so forth: | |
173 | maps.visit_body(body); | |
174 | ||
175 | // compute liveness | |
176 | let mut lsets = Liveness::new(&mut maps, local_def_id); | |
177 | let entry_ln = lsets.compute(&body, hir_id); | |
178 | lsets.log_liveness(entry_ln, body_id.hir_id); | |
179 | ||
180 | // check for various error conditions | |
181 | lsets.visit_body(body); | |
182 | lsets.warn_about_unused_upvars(entry_ln); | |
183 | lsets.warn_about_unused_args(body, entry_ln); | |
9fa01778 XL |
184 | } |
185 | ||
f035d41b | 186 | pub fn provide(providers: &mut Providers) { |
f2b60f7d | 187 | *providers = Providers { check_liveness, ..*providers }; |
223e47cc LB |
188 | } |
189 | ||
223e47cc LB |
190 | // ______________________________________________________________________ |
191 | // Creating ir_maps | |
192 | // | |
193 | // This is the first pass and the one that drives the main | |
6522a427 | 194 | // computation. It walks up and down the IR once. On the way down, |
223e47cc | 195 | // we count for each function the number of variables as well as |
6522a427 | 196 | // liveness nodes. A liveness node is basically an expression or |
223e47cc LB |
197 | // capture clause that does something of interest: either it has |
198 | // interesting control flow or it uses/defines a local variable. | |
199 | // | |
200 | // On the way back up, at each function node we create liveness sets | |
201 | // (we now know precisely how big to make our various vectors and so | |
202 | // forth) and then do the data-flow propagation to compute the set | |
203 | // of live variables at each program point. | |
204 | // | |
205 | // Finally, we run back over the IR one last time and, using the | |
6522a427 | 206 | // computed liveness, check various safety conditions. For example, |
223e47cc | 207 | // there must be no live nodes at the definition site for a variable |
6522a427 | 208 | // unless it has an initializer. Similarly, each non-mutable local |
223e47cc | 209 | // variable must not be assigned if there is some successor |
6522a427 | 210 | // assignment. And so forth. |
223e47cc | 211 | |
223e47cc LB |
212 | struct CaptureInfo { |
213 | ln: LiveNode, | |
dfeec247 | 214 | var_hid: HirId, |
223e47cc LB |
215 | } |
216 | ||
c34b1796 | 217 | #[derive(Copy, Clone, Debug)] |
223e47cc | 218 | struct LocalInfo { |
94b46f34 | 219 | id: HirId, |
f9f354fc | 220 | name: Symbol, |
2c00a5a8 | 221 | is_shorthand: bool, |
223e47cc LB |
222 | } |
223 | ||
c34b1796 | 224 | #[derive(Copy, Clone, Debug)] |
223e47cc | 225 | enum VarKind { |
f9f354fc | 226 | Param(HirId, Symbol), |
223e47cc | 227 | Local(LocalInfo), |
f9f354fc | 228 | Upvar(HirId, Symbol), |
223e47cc LB |
229 | } |
230 | ||
f2b60f7d FG |
231 | struct CollectLitsVisitor<'tcx> { |
232 | lit_exprs: Vec<&'tcx hir::Expr<'tcx>>, | |
233 | } | |
234 | ||
235 | impl<'tcx> Visitor<'tcx> for CollectLitsVisitor<'tcx> { | |
236 | fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { | |
237 | if let hir::ExprKind::Lit(_) = expr.kind { | |
238 | self.lit_exprs.push(expr); | |
239 | } | |
240 | intravisit::walk_expr(self, expr); | |
241 | } | |
242 | } | |
243 | ||
dc9dc135 XL |
244 | struct IrMaps<'tcx> { |
245 | tcx: TyCtxt<'tcx>, | |
94b46f34 XL |
246 | live_node_map: HirIdMap<LiveNode>, |
247 | variable_map: HirIdMap<Variable>, | |
532ac7d7 | 248 | capture_info_map: HirIdMap<Rc<Vec<CaptureInfo>>>, |
1b1a35ee XL |
249 | var_kinds: IndexVec<Variable, VarKind>, |
250 | lnks: IndexVec<LiveNode, LiveNodeKind>, | |
223e47cc LB |
251 | } |
252 | ||
a2a8927a | 253 | impl<'tcx> IrMaps<'tcx> { |
1b1a35ee | 254 | fn new(tcx: TyCtxt<'tcx>) -> IrMaps<'tcx> { |
1a4d82fc | 255 | IrMaps { |
041b39d2 | 256 | tcx, |
a1dfa0c6 XL |
257 | live_node_map: HirIdMap::default(), |
258 | variable_map: HirIdMap::default(), | |
259 | capture_info_map: Default::default(), | |
1b1a35ee XL |
260 | var_kinds: IndexVec::new(), |
261 | lnks: IndexVec::new(), | |
1a4d82fc | 262 | } |
223e47cc | 263 | } |
223e47cc | 264 | |
1a4d82fc | 265 | fn add_live_node(&mut self, lnk: LiveNodeKind) -> LiveNode { |
1b1a35ee | 266 | let ln = self.lnks.push(lnk); |
223e47cc | 267 | |
dfeec247 | 268 | debug!("{:?} is of kind {}", ln, live_node_kind_to_string(lnk, self.tcx)); |
223e47cc LB |
269 | |
270 | ln | |
271 | } | |
272 | ||
94b46f34 | 273 | fn add_live_node_for_node(&mut self, hir_id: HirId, lnk: LiveNodeKind) { |
223e47cc | 274 | let ln = self.add_live_node(lnk); |
94b46f34 | 275 | self.live_node_map.insert(hir_id, ln); |
223e47cc | 276 | |
94b46f34 | 277 | debug!("{:?} is node {:?}", ln, hir_id); |
223e47cc LB |
278 | } |
279 | ||
1a4d82fc | 280 | fn add_variable(&mut self, vk: VarKind) -> Variable { |
1b1a35ee | 281 | let v = self.var_kinds.push(vk); |
223e47cc LB |
282 | |
283 | match vk { | |
f9f354fc | 284 | Local(LocalInfo { id: node_id, .. }) | Param(node_id, _) | Upvar(node_id, _) => { |
223e47cc | 285 | self.variable_map.insert(node_id, v); |
dfeec247 | 286 | } |
223e47cc LB |
287 | } |
288 | ||
1a4d82fc | 289 | debug!("{:?} is {:?}", v, vk); |
223e47cc LB |
290 | |
291 | v | |
292 | } | |
293 | ||
94b46f34 XL |
294 | fn variable(&self, hir_id: HirId, span: Span) -> Variable { |
295 | match self.variable_map.get(&hir_id) { | |
54a0048b SL |
296 | Some(&var) => var, |
297 | None => { | |
94b46f34 | 298 | span_bug!(span, "no variable registered for id {:?}", hir_id); |
54a0048b | 299 | } |
223e47cc LB |
300 | } |
301 | } | |
302 | ||
1b1a35ee XL |
303 | fn variable_name(&self, var: Variable) -> Symbol { |
304 | match self.var_kinds[var] { | |
305 | Local(LocalInfo { name, .. }) | Param(_, name) | Upvar(_, name) => name, | |
223e47cc LB |
306 | } |
307 | } | |
308 | ||
2c00a5a8 | 309 | fn variable_is_shorthand(&self, var: Variable) -> bool { |
1b1a35ee | 310 | match self.var_kinds[var] { |
2c00a5a8 | 311 | Local(LocalInfo { is_shorthand, .. }) => is_shorthand, |
f9f354fc | 312 | Param(..) | Upvar(..) => false, |
2c00a5a8 XL |
313 | } |
314 | } | |
315 | ||
532ac7d7 XL |
316 | fn set_captures(&mut self, hir_id: HirId, cs: Vec<CaptureInfo>) { |
317 | self.capture_info_map.insert(hir_id, Rc::new(cs)); | |
223e47cc LB |
318 | } |
319 | ||
c295e0f8 | 320 | fn collect_shorthand_field_ids(&self, pat: &hir::Pat<'tcx>) -> HirIdSet { |
1b1a35ee XL |
321 | // For struct patterns, take note of which fields used shorthand |
322 | // (`x` rather than `x: x`). | |
323 | let mut shorthand_field_ids = HirIdSet::default(); | |
324 | let mut pats = VecDeque::new(); | |
325 | pats.push_back(pat); | |
c295e0f8 | 326 | |
1b1a35ee XL |
327 | while let Some(pat) = pats.pop_front() { |
328 | use rustc_hir::PatKind::*; | |
329 | match &pat.kind { | |
330 | Binding(.., inner_pat) => { | |
331 | pats.extend(inner_pat.iter()); | |
332 | } | |
333 | Struct(_, fields, _) => { | |
064997fb | 334 | let (short, not_short): (Vec<_>, _) = |
c295e0f8 XL |
335 | fields.iter().partition(|f| f.is_shorthand); |
336 | shorthand_field_ids.extend(short.iter().map(|f| f.pat.hir_id)); | |
337 | pats.extend(not_short.iter().map(|f| f.pat)); | |
1b1a35ee XL |
338 | } |
339 | Ref(inner_pat, _) | Box(inner_pat) => { | |
340 | pats.push_back(inner_pat); | |
341 | } | |
342 | TupleStruct(_, inner_pats, _) | Tuple(inner_pats, _) | Or(inner_pats) => { | |
343 | pats.extend(inner_pats.iter()); | |
344 | } | |
345 | Slice(pre_pats, inner_pat, post_pats) => { | |
346 | pats.extend(pre_pats.iter()); | |
347 | pats.extend(inner_pat.iter()); | |
348 | pats.extend(post_pats.iter()); | |
349 | } | |
350 | _ => {} | |
351 | } | |
352 | } | |
353 | ||
064997fb | 354 | shorthand_field_ids |
c295e0f8 XL |
355 | } |
356 | ||
357 | fn add_from_pat(&mut self, pat: &hir::Pat<'tcx>) { | |
358 | let shorthand_field_ids = self.collect_shorthand_field_ids(pat); | |
359 | ||
1b1a35ee | 360 | pat.each_binding(|_, hir_id, _, ident| { |
94222f64 | 361 | self.add_live_node_for_node(hir_id, VarDefNode(ident.span, hir_id)); |
1b1a35ee XL |
362 | self.add_variable(Local(LocalInfo { |
363 | id: hir_id, | |
364 | name: ident.name, | |
365 | is_shorthand: shorthand_field_ids.contains(&hir_id), | |
366 | })); | |
367 | }); | |
223e47cc | 368 | } |
1a4d82fc | 369 | } |
223e47cc | 370 | |
1b1a35ee | 371 | impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> { |
1b1a35ee XL |
372 | fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) { |
373 | self.add_from_pat(&local.pat); | |
064997fb FG |
374 | if local.els.is_some() { |
375 | self.add_live_node_for_node(local.hir_id, ExprNode(local.span, local.hir_id)); | |
376 | } | |
1b1a35ee XL |
377 | intravisit::walk_local(self, local); |
378 | } | |
379 | ||
380 | fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) { | |
381 | self.add_from_pat(&arm.pat); | |
923072b8 FG |
382 | if let Some(hir::Guard::IfLet(ref let_expr)) = arm.guard { |
383 | self.add_from_pat(let_expr.pat); | |
fc512014 | 384 | } |
1b1a35ee | 385 | intravisit::walk_arm(self, arm); |
f9f354fc XL |
386 | } |
387 | ||
1b1a35ee | 388 | fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) { |
c295e0f8 | 389 | let shorthand_field_ids = self.collect_shorthand_field_ids(param.pat); |
e1599b0c | 390 | param.pat.each_binding(|_bm, hir_id, _x, ident| { |
6a06907d | 391 | let var = match param.pat.kind { |
c295e0f8 | 392 | rustc_hir::PatKind::Struct(..) => Local(LocalInfo { |
6a06907d XL |
393 | id: hir_id, |
394 | name: ident.name, | |
c295e0f8 | 395 | is_shorthand: shorthand_field_ids.contains(&hir_id), |
6a06907d XL |
396 | }), |
397 | _ => Param(hir_id, ident.name), | |
532ac7d7 | 398 | }; |
1b1a35ee XL |
399 | self.add_variable(var); |
400 | }); | |
401 | intravisit::walk_param(self, param); | |
dfeec247 | 402 | } |
223e47cc | 403 | |
1b1a35ee XL |
404 | fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { |
405 | match expr.kind { | |
406 | // live nodes required for uses or definitions of variables: | |
407 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { | |
408 | debug!("expr {}: path that leads to {:?}", expr.hir_id, path.res); | |
409 | if let Res::Local(_var_hir_id) = path.res { | |
94222f64 | 410 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id)); |
1b1a35ee XL |
411 | } |
412 | intravisit::walk_expr(self, expr); | |
94b46f34 | 413 | } |
6522a427 | 414 | hir::ExprKind::Closure(closure) => { |
1b1a35ee XL |
415 | // Interesting control flow (for loops can contain labeled |
416 | // breaks or continues) | |
94222f64 | 417 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id)); |
1b1a35ee | 418 | |
94222f64 | 419 | // Make a live_node for each mentioned variable, with the span |
6522a427 | 420 | // being the location that the variable is used. This results |
1b1a35ee XL |
421 | // in better error messages than just pointing at the closure |
422 | // construction site. | |
423 | let mut call_caps = Vec::new(); | |
6522a427 | 424 | if let Some(upvars) = self.tcx.upvars_mentioned(closure.def_id) { |
94222f64 | 425 | call_caps.extend(upvars.keys().map(|var_id| { |
fc512014 | 426 | let upvar = upvars[var_id]; |
1b1a35ee | 427 | let upvar_ln = self.add_live_node(UpvarNode(upvar.span)); |
fc512014 | 428 | CaptureInfo { ln: upvar_ln, var_hid: *var_id } |
1b1a35ee XL |
429 | })); |
430 | } | |
431 | self.set_captures(expr.hir_id, call_caps); | |
432 | intravisit::walk_expr(self, expr); | |
94b46f34 | 433 | } |
94b46f34 | 434 | |
a2a8927a XL |
435 | hir::ExprKind::Let(let_expr) => { |
436 | self.add_from_pat(let_expr.pat); | |
94222f64 XL |
437 | intravisit::walk_expr(self, expr); |
438 | } | |
439 | ||
1b1a35ee | 440 | // live nodes required for interesting control flow: |
94222f64 XL |
441 | hir::ExprKind::If(..) |
442 | | hir::ExprKind::Match(..) | |
443 | | hir::ExprKind::Loop(..) | |
444 | | hir::ExprKind::Yield(..) => { | |
445 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id)); | |
1b1a35ee | 446 | intravisit::walk_expr(self, expr); |
dc9dc135 | 447 | } |
1b1a35ee | 448 | hir::ExprKind::Binary(op, ..) if op.node.is_lazy() => { |
94222f64 | 449 | self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id)); |
1b1a35ee | 450 | intravisit::walk_expr(self, expr); |
dfeec247 | 451 | } |
dfeec247 | 452 | |
1b1a35ee XL |
453 | // otherwise, live nodes are not required: |
454 | hir::ExprKind::Index(..) | |
455 | | hir::ExprKind::Field(..) | |
456 | | hir::ExprKind::Array(..) | |
457 | | hir::ExprKind::Call(..) | |
458 | | hir::ExprKind::MethodCall(..) | |
459 | | hir::ExprKind::Tup(..) | |
460 | | hir::ExprKind::Binary(..) | |
461 | | hir::ExprKind::AddrOf(..) | |
462 | | hir::ExprKind::Cast(..) | |
463 | | hir::ExprKind::DropTemps(..) | |
464 | | hir::ExprKind::Unary(..) | |
465 | | hir::ExprKind::Break(..) | |
466 | | hir::ExprKind::Continue(_) | |
467 | | hir::ExprKind::Lit(_) | |
29967ef6 | 468 | | hir::ExprKind::ConstBlock(..) |
1b1a35ee XL |
469 | | hir::ExprKind::Ret(..) |
470 | | hir::ExprKind::Block(..) | |
471 | | hir::ExprKind::Assign(..) | |
472 | | hir::ExprKind::AssignOp(..) | |
473 | | hir::ExprKind::Struct(..) | |
474 | | hir::ExprKind::Repeat(..) | |
475 | | hir::ExprKind::InlineAsm(..) | |
1b1a35ee | 476 | | hir::ExprKind::Box(..) |
1b1a35ee XL |
477 | | hir::ExprKind::Type(..) |
478 | | hir::ExprKind::Err | |
479 | | hir::ExprKind::Path(hir::QPath::TypeRelative(..)) | |
480 | | hir::ExprKind::Path(hir::QPath::LangItem(..)) => { | |
481 | intravisit::walk_expr(self, expr); | |
482 | } | |
48663c56 | 483 | } |
223e47cc LB |
484 | } |
485 | } | |
486 | ||
487 | // ______________________________________________________________________ | |
488 | // Computing liveness sets | |
489 | // | |
490 | // Actually we compute just a bit more than just liveness, but we use | |
491 | // the same basic propagation framework in all cases. | |
492 | ||
c34b1796 AL |
493 | const ACC_READ: u32 = 1; |
494 | const ACC_WRITE: u32 = 2; | |
495 | const ACC_USE: u32 = 4; | |
223e47cc | 496 | |
dc9dc135 XL |
497 | struct Liveness<'a, 'tcx> { |
498 | ir: &'a mut IrMaps<'tcx>, | |
3dfed10e | 499 | typeck_results: &'a ty::TypeckResults<'tcx>, |
ba9703b0 | 500 | param_env: ty::ParamEnv<'tcx>, |
6a06907d | 501 | closure_min_captures: Option<&'tcx RootVariableMinCaptureList<'tcx>>, |
1b1a35ee | 502 | successors: IndexVec<LiveNode, Option<LiveNode>>, |
fc512014 | 503 | rwu_table: rwu_table::RWUTable, |
cc61c64b | 504 | |
1b1a35ee XL |
505 | /// A live node representing a point of execution before closure entry & |
506 | /// after closure exit. Used to calculate liveness of captured variables | |
507 | /// through calls to the same closure. Used for Fn & FnMut closures only. | |
508 | closure_ln: LiveNode, | |
509 | /// A live node representing every 'exit' from the function, whether it be | |
510 | /// by explicit return, panic, or other means. | |
511 | exit_ln: LiveNode, | |
512 | ||
223e47cc LB |
513 | // mappings from loop node ID to LiveNode |
514 | // ("break" label should map to loop node ID, | |
515 | // it probably doesn't now) | |
532ac7d7 XL |
516 | break_ln: HirIdMap<LiveNode>, |
517 | cont_ln: HirIdMap<LiveNode>, | |
223e47cc LB |
518 | } |
519 | ||
1a4d82fc | 520 | impl<'a, 'tcx> Liveness<'a, 'tcx> { |
1b1a35ee XL |
521 | fn new(ir: &'a mut IrMaps<'tcx>, body_owner: LocalDefId) -> Liveness<'a, 'tcx> { |
522 | let typeck_results = ir.tcx.typeck(body_owner); | |
523 | let param_env = ir.tcx.param_env(body_owner); | |
064997fb | 524 | let closure_min_captures = typeck_results.closure_min_captures.get(&body_owner); |
1b1a35ee XL |
525 | let closure_ln = ir.add_live_node(ClosureNode); |
526 | let exit_ln = ir.add_live_node(ExitNode); | |
32a655c1 | 527 | |
1b1a35ee XL |
528 | let num_live_nodes = ir.lnks.len(); |
529 | let num_vars = ir.var_kinds.len(); | |
32a655c1 | 530 | |
1a4d82fc | 531 | Liveness { |
041b39d2 | 532 | ir, |
3dfed10e | 533 | typeck_results, |
ba9703b0 | 534 | param_env, |
6a06907d | 535 | closure_min_captures, |
1b1a35ee | 536 | successors: IndexVec::from_elem_n(None, num_live_nodes), |
fc512014 | 537 | rwu_table: rwu_table::RWUTable::new(num_live_nodes, num_vars), |
1b1a35ee XL |
538 | closure_ln, |
539 | exit_ln, | |
a1dfa0c6 XL |
540 | break_ln: Default::default(), |
541 | cont_ln: Default::default(), | |
1a4d82fc | 542 | } |
223e47cc | 543 | } |
223e47cc | 544 | |
94b46f34 XL |
545 | fn live_node(&self, hir_id: HirId, span: Span) -> LiveNode { |
546 | match self.ir.live_node_map.get(&hir_id) { | |
dfeec247 XL |
547 | Some(&ln) => ln, |
548 | None => { | |
549 | // This must be a mismatch between the ir_map construction | |
550 | // above and the propagation code below; the two sets of | |
551 | // code have to agree about which AST nodes are worth | |
552 | // creating liveness nodes for. | |
553 | span_bug!(span, "no live node registered for node {:?}", hir_id); | |
554 | } | |
223e47cc LB |
555 | } |
556 | } | |
557 | ||
94b46f34 XL |
558 | fn variable(&self, hir_id: HirId, span: Span) -> Variable { |
559 | self.ir.variable(hir_id, span) | |
223e47cc LB |
560 | } |
561 | ||
dfeec247 | 562 | fn define_bindings_in_pat(&mut self, pat: &hir::Pat<'_>, mut succ: LiveNode) -> LiveNode { |
e74abb32 XL |
563 | // In an or-pattern, only consider the first pattern; any later patterns |
564 | // must have the same bindings, and we also consider the first pattern | |
565 | // to be the "authoritative" set of ids. | |
566 | pat.each_binding_or_first(&mut |_, hir_id, pat_sp, ident| { | |
567 | let ln = self.live_node(hir_id, pat_sp); | |
568 | let var = self.variable(hir_id, ident.span); | |
569 | self.init_from_succ(ln, succ); | |
570 | self.define(ln, var); | |
223e47cc | 571 | succ = ln; |
1a4d82fc | 572 | }); |
223e47cc LB |
573 | succ |
574 | } | |
575 | ||
fc512014 XL |
576 | fn live_on_entry(&self, ln: LiveNode, var: Variable) -> bool { |
577 | self.rwu_table.get_reader(ln, var) | |
223e47cc LB |
578 | } |
579 | ||
0bf4aa26 | 580 | // Is this variable live on entry to any of its successor nodes? |
fc512014 | 581 | fn live_on_exit(&self, ln: LiveNode, var: Variable) -> bool { |
1b1a35ee | 582 | let successor = self.successors[ln].unwrap(); |
1a4d82fc | 583 | self.live_on_entry(successor, var) |
223e47cc LB |
584 | } |
585 | ||
1a4d82fc | 586 | fn used_on_entry(&self, ln: LiveNode, var: Variable) -> bool { |
fc512014 | 587 | self.rwu_table.get_used(ln, var) |
223e47cc LB |
588 | } |
589 | ||
fc512014 XL |
590 | fn assigned_on_entry(&self, ln: LiveNode, var: Variable) -> bool { |
591 | self.rwu_table.get_writer(ln, var) | |
223e47cc LB |
592 | } |
593 | ||
fc512014 | 594 | fn assigned_on_exit(&self, ln: LiveNode, var: Variable) -> bool { |
1b1a35ee | 595 | let successor = self.successors[ln].unwrap(); |
1a4d82fc | 596 | self.assigned_on_entry(successor, var) |
223e47cc LB |
597 | } |
598 | ||
fc512014 | 599 | fn write_vars<F>(&self, wr: &mut dyn Write, mut test: F) -> io::Result<()> |
dfeec247 | 600 | where |
fc512014 | 601 | F: FnMut(Variable) -> bool, |
1a4d82fc | 602 | { |
1b1a35ee | 603 | for var_idx in 0..self.ir.var_kinds.len() { |
fc512014 XL |
604 | let var = Variable::from(var_idx); |
605 | if test(var) { | |
606 | write!(wr, " {:?}", var)?; | |
223e47cc LB |
607 | } |
608 | } | |
1a4d82fc | 609 | Ok(()) |
223e47cc LB |
610 | } |
611 | ||
1a4d82fc JJ |
612 | #[allow(unused_must_use)] |
613 | fn ln_str(&self, ln: LiveNode) -> String { | |
614 | let mut wr = Vec::new(); | |
615 | { | |
0531ce1d | 616 | let wr = &mut wr as &mut dyn Write; |
1b1a35ee | 617 | write!(wr, "[{:?} of kind {:?} reads", ln, self.ir.lnks[ln]); |
fc512014 | 618 | self.write_vars(wr, |var| self.rwu_table.get_reader(ln, var)); |
1a4d82fc | 619 | write!(wr, " writes"); |
fc512014 | 620 | self.write_vars(wr, |var| self.rwu_table.get_writer(ln, var)); |
f9f354fc | 621 | write!(wr, " uses"); |
fc512014 | 622 | self.write_vars(wr, |var| self.rwu_table.get_used(ln, var)); |
f9f354fc | 623 | |
1b1a35ee | 624 | write!(wr, " precedes {:?}]", self.successors[ln]); |
223e47cc | 625 | } |
1a4d82fc | 626 | String::from_utf8(wr).unwrap() |
223e47cc LB |
627 | } |
628 | ||
f9f354fc XL |
629 | fn log_liveness(&self, entry_ln: LiveNode, hir_id: hir::HirId) { |
630 | // hack to skip the loop unless debug! is enabled: | |
631 | debug!( | |
632 | "^^ liveness computation results for body {} (entry={:?})", | |
633 | { | |
1b1a35ee XL |
634 | for ln_idx in 0..self.ir.lnks.len() { |
635 | debug!("{:?}", self.ln_str(LiveNode::from(ln_idx))); | |
f9f354fc XL |
636 | } |
637 | hir_id | |
638 | }, | |
639 | entry_ln | |
640 | ); | |
641 | } | |
642 | ||
1a4d82fc | 643 | fn init_empty(&mut self, ln: LiveNode, succ_ln: LiveNode) { |
1b1a35ee | 644 | self.successors[ln] = Some(succ_ln); |
223e47cc | 645 | |
0bf4aa26 | 646 | // It is not necessary to initialize the RWUs here because they are all |
fc512014 | 647 | // empty when created, and the sets only grow during iterations. |
223e47cc LB |
648 | } |
649 | ||
1a4d82fc | 650 | fn init_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode) { |
223e47cc | 651 | // more efficient version of init_empty() / merge_from_succ() |
1b1a35ee | 652 | self.successors[ln] = Some(succ_ln); |
fc512014 | 653 | self.rwu_table.copy(ln, succ_ln); |
dfeec247 | 654 | debug!("init_from_succ(ln={}, succ={})", self.ln_str(ln), self.ln_str(succ_ln)); |
223e47cc LB |
655 | } |
656 | ||
fc512014 | 657 | fn merge_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode) -> bool { |
dfeec247 XL |
658 | if ln == succ_ln { |
659 | return false; | |
660 | } | |
223e47cc | 661 | |
fc512014 XL |
662 | let changed = self.rwu_table.union(ln, succ_ln); |
663 | debug!("merge_from_succ(ln={:?}, succ={}, changed={})", ln, self.ln_str(succ_ln), changed); | |
664 | changed | |
223e47cc LB |
665 | } |
666 | ||
667 | // Indicates that a local variable was *defined*; we know that no | |
668 | // uses of the variable can precede the definition (resolve checks | |
669 | // this) so we just clear out all the data. | |
1a4d82fc | 670 | fn define(&mut self, writer: LiveNode, var: Variable) { |
fc512014 XL |
671 | let used = self.rwu_table.get_used(writer, var); |
672 | self.rwu_table.set(writer, var, rwu_table::RWU { reader: false, writer: false, used }); | |
673 | debug!("{:?} defines {:?}: {}", writer, var, self.ln_str(writer)); | |
223e47cc LB |
674 | } |
675 | ||
676 | // Either read, write, or both depending on the acc bitset | |
c34b1796 | 677 | fn acc(&mut self, ln: LiveNode, var: Variable, acc: u32) { |
dfeec247 | 678 | debug!("{:?} accesses[{:x}] {:?}: {}", ln, acc, var, self.ln_str(ln)); |
1a4d82fc | 679 | |
fc512014 | 680 | let mut rwu = self.rwu_table.get(ln, var); |
223e47cc LB |
681 | |
682 | if (acc & ACC_WRITE) != 0 { | |
fc512014 XL |
683 | rwu.reader = false; |
684 | rwu.writer = true; | |
223e47cc LB |
685 | } |
686 | ||
687 | // Important: if we both read/write, must do read second | |
688 | // or else the write will override. | |
689 | if (acc & ACC_READ) != 0 { | |
fc512014 | 690 | rwu.reader = true; |
223e47cc LB |
691 | } |
692 | ||
693 | if (acc & ACC_USE) != 0 { | |
0bf4aa26 | 694 | rwu.used = true; |
223e47cc | 695 | } |
223e47cc | 696 | |
fc512014 | 697 | self.rwu_table.set(ln, var, rwu); |
0bf4aa26 | 698 | } |
223e47cc | 699 | |
1b1a35ee XL |
700 | fn compute(&mut self, body: &hir::Body<'_>, hir_id: HirId) -> LiveNode { |
701 | debug!("compute: for body {:?}", body.id().hir_id); | |
223e47cc | 702 | |
f9f354fc XL |
703 | // # Liveness of captured variables |
704 | // | |
705 | // When computing the liveness for captured variables we take into | |
706 | // account how variable is captured (ByRef vs ByValue) and what is the | |
707 | // closure kind (Generator / FnOnce vs Fn / FnMut). | |
708 | // | |
709 | // Variables captured by reference are assumed to be used on the exit | |
710 | // from the closure. | |
711 | // | |
712 | // In FnOnce closures, variables captured by value are known to be dead | |
713 | // on exit since it is impossible to call the closure again. | |
714 | // | |
715 | // In Fn / FnMut closures, variables captured by value are live on exit | |
716 | // if they are live on the entry to the closure, since only the closure | |
717 | // itself can access them on subsequent calls. | |
718 | ||
6a06907d | 719 | if let Some(closure_min_captures) = self.closure_min_captures { |
f9f354fc | 720 | // Mark upvars captured by reference as used after closure exits. |
6a06907d XL |
721 | for (&var_hir_id, min_capture_list) in closure_min_captures { |
722 | for captured_place in min_capture_list { | |
723 | match captured_place.info.capture_kind { | |
724 | ty::UpvarCapture::ByRef(_) => { | |
725 | let var = self.variable( | |
726 | var_hir_id, | |
727 | captured_place.get_capture_kind_span(self.ir.tcx), | |
728 | ); | |
729 | self.acc(self.exit_ln, var, ACC_READ | ACC_USE); | |
730 | } | |
5099ac24 | 731 | ty::UpvarCapture::ByValue => {} |
f9f354fc | 732 | } |
f9f354fc XL |
733 | } |
734 | } | |
735 | } | |
cc61c64b | 736 | |
1b1a35ee | 737 | let succ = self.propagate_through_expr(&body.value, self.exit_ln); |
223e47cc | 738 | |
6a06907d | 739 | if self.closure_min_captures.is_none() { |
1b1a35ee XL |
740 | // Either not a closure, or closure without any captured variables. |
741 | // No need to determine liveness of captured variables, since there | |
742 | // are none. | |
743 | return succ; | |
f9f354fc XL |
744 | } |
745 | ||
1b1a35ee XL |
746 | let ty = self.typeck_results.node_type(hir_id); |
747 | match ty.kind() { | |
f9f354fc XL |
748 | ty::Closure(_def_id, substs) => match substs.as_closure().kind() { |
749 | ty::ClosureKind::Fn => {} | |
750 | ty::ClosureKind::FnMut => {} | |
751 | ty::ClosureKind::FnOnce => return succ, | |
dfeec247 | 752 | }, |
f9f354fc XL |
753 | ty::Generator(..) => return succ, |
754 | _ => { | |
1b1a35ee XL |
755 | span_bug!( |
756 | body.value.span, | |
757 | "{} has upvars so it should have a closure type: {:?}", | |
758 | hir_id, | |
759 | ty | |
760 | ); | |
f9f354fc XL |
761 | } |
762 | }; | |
763 | ||
764 | // Propagate through calls to the closure. | |
f9f354fc | 765 | loop { |
1b1a35ee | 766 | self.init_from_succ(self.closure_ln, succ); |
f9f354fc XL |
767 | for param in body.params { |
768 | param.pat.each_binding(|_bm, hir_id, _x, ident| { | |
769 | let var = self.variable(hir_id, ident.span); | |
1b1a35ee | 770 | self.define(self.closure_ln, var); |
f9f354fc XL |
771 | }) |
772 | } | |
223e47cc | 773 | |
fc512014 | 774 | if !self.merge_from_succ(self.exit_ln, self.closure_ln) { |
f9f354fc XL |
775 | break; |
776 | } | |
1b1a35ee | 777 | assert_eq!(succ, self.propagate_through_expr(&body.value, self.exit_ln)); |
f9f354fc XL |
778 | } |
779 | ||
780 | succ | |
223e47cc LB |
781 | } |
782 | ||
dfeec247 | 783 | fn propagate_through_block(&mut self, blk: &hir::Block<'_>, succ: LiveNode) -> LiveNode { |
cc61c64b | 784 | if blk.targeted_by_break { |
532ac7d7 | 785 | self.break_ln.insert(blk.hir_id, succ); |
cc61c64b | 786 | } |
c295e0f8 | 787 | let succ = self.propagate_through_opt_expr(blk.expr, succ); |
dfeec247 | 788 | blk.stmts.iter().rev().fold(succ, |succ, stmt| self.propagate_through_stmt(stmt, succ)) |
223e47cc LB |
789 | } |
790 | ||
dfeec247 | 791 | fn propagate_through_stmt(&mut self, stmt: &hir::Stmt<'_>, succ: LiveNode) -> LiveNode { |
e74abb32 | 792 | match stmt.kind { |
9fa01778 XL |
793 | hir::StmtKind::Local(ref local) => { |
794 | // Note: we mark the variable as defined regardless of whether | |
6522a427 | 795 | // there is an initializer. Initially I had thought to only mark |
9fa01778 XL |
796 | // the live variable as defined if it was initialized, and then we |
797 | // could check for uninit variables just by scanning what is live | |
798 | // at the start of the function. But that doesn't work so well for | |
799 | // immutable variables defined in a loop: | |
800 | // loop { let x; x = 5; } | |
801 | // because the "assignment" loops back around and generates an error. | |
802 | // | |
803 | // So now we just check that variables defined w/o an | |
804 | // initializer are not live at the point of their | |
805 | // initialization, which is mildly more complex than checking | |
806 | // once at the func header but otherwise equivalent. | |
223e47cc | 807 | |
064997fb FG |
808 | if let Some(els) = local.els { |
809 | // Eventually, `let pat: ty = init else { els };` is mostly equivalent to | |
810 | // `let (bindings, ...) = match init { pat => (bindings, ...), _ => els };` | |
811 | // except that extended lifetime applies at the `init` location. | |
812 | // | |
813 | // (e) | |
814 | // | | |
815 | // v | |
816 | // (expr) | |
817 | // / \ | |
818 | // | | | |
819 | // v v | |
820 | // bindings els | |
821 | // | | |
822 | // v | |
823 | // ( succ ) | |
824 | // | |
825 | if let Some(init) = local.init { | |
826 | let else_ln = self.propagate_through_block(els, succ); | |
827 | let ln = self.live_node(local.hir_id, local.span); | |
828 | self.init_from_succ(ln, succ); | |
829 | self.merge_from_succ(ln, else_ln); | |
830 | let succ = self.propagate_through_expr(init, ln); | |
831 | self.define_bindings_in_pat(&local.pat, succ) | |
832 | } else { | |
833 | span_bug!( | |
834 | stmt.span, | |
835 | "variable is uninitialized but an unexpected else branch is found" | |
836 | ) | |
837 | } | |
838 | } else { | |
839 | let succ = self.propagate_through_opt_expr(local.init, succ); | |
840 | self.define_bindings_in_pat(&local.pat, succ) | |
841 | } | |
1a4d82fc | 842 | } |
9fa01778 XL |
843 | hir::StmtKind::Item(..) => succ, |
844 | hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => { | |
845 | self.propagate_through_expr(&expr, succ) | |
223e47cc | 846 | } |
223e47cc LB |
847 | } |
848 | } | |
849 | ||
dfeec247 XL |
850 | fn propagate_through_exprs(&mut self, exprs: &[Expr<'_>], succ: LiveNode) -> LiveNode { |
851 | exprs.iter().rev().fold(succ, |succ, expr| self.propagate_through_expr(&expr, succ)) | |
223e47cc LB |
852 | } |
853 | ||
dfeec247 XL |
854 | fn propagate_through_opt_expr( |
855 | &mut self, | |
856 | opt_expr: Option<&Expr<'_>>, | |
857 | succ: LiveNode, | |
858 | ) -> LiveNode { | |
1a4d82fc | 859 | opt_expr.map_or(succ, |expr| self.propagate_through_expr(expr, succ)) |
223e47cc LB |
860 | } |
861 | ||
dfeec247 | 862 | fn propagate_through_expr(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode { |
ba9703b0 | 863 | debug!("propagate_through_expr: {:?}", expr); |
223e47cc | 864 | |
e74abb32 | 865 | match expr.kind { |
0bf4aa26 XL |
866 | // Interesting cases with control flow or which gen/kill |
867 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { | |
868 | self.access_path(expr.hir_id, path, succ, ACC_READ | ACC_USE) | |
869 | } | |
223e47cc | 870 | |
dfeec247 | 871 | hir::ExprKind::Field(ref e, _) => self.propagate_through_expr(&e, succ), |
1a4d82fc | 872 | |
923072b8 | 873 | hir::ExprKind::Closure { .. } => { |
ba9703b0 | 874 | debug!("{:?} is an ExprKind::Closure", expr); |
0bf4aa26 | 875 | |
0bf4aa26 XL |
876 | // the construction of a closure itself is not important, |
877 | // but we have to consider the closed over variables. | |
dfeec247 XL |
878 | let caps = self |
879 | .ir | |
880 | .capture_info_map | |
881 | .get(&expr.hir_id) | |
882 | .cloned() | |
883 | .unwrap_or_else(|| span_bug!(expr.span, "no registered caps")); | |
0bf4aa26 XL |
884 | |
885 | caps.iter().rev().fold(succ, |succ, cap| { | |
886 | self.init_from_succ(cap.ln, succ); | |
887 | let var = self.variable(cap.var_hid, expr.span); | |
888 | self.acc(cap.ln, var, ACC_READ | ACC_USE); | |
889 | cap.ln | |
890 | }) | |
891 | } | |
223e47cc | 892 | |
a2a8927a XL |
893 | hir::ExprKind::Let(let_expr) => { |
894 | let succ = self.propagate_through_expr(let_expr.init, succ); | |
895 | self.define_bindings_in_pat(let_expr.pat, succ) | |
94222f64 XL |
896 | } |
897 | ||
0bf4aa26 XL |
898 | // Note that labels have been resolved, so we don't need to look |
899 | // at the label ident | |
5869c6ff XL |
900 | hir::ExprKind::Loop(ref blk, ..) => self.propagate_through_loop(expr, &blk, succ), |
901 | ||
94222f64 XL |
902 | hir::ExprKind::Yield(ref e, ..) => { |
903 | let yield_ln = self.live_node(expr.hir_id, expr.span); | |
904 | self.init_from_succ(yield_ln, succ); | |
905 | self.merge_from_succ(yield_ln, self.exit_ln); | |
906 | self.propagate_through_expr(e, yield_ln) | |
907 | } | |
908 | ||
5869c6ff XL |
909 | hir::ExprKind::If(ref cond, ref then, ref else_opt) => { |
910 | // | |
911 | // (cond) | |
912 | // | | |
913 | // v | |
914 | // (expr) | |
915 | // / \ | |
916 | // | | | |
917 | // v v | |
918 | // (then)(els) | |
919 | // | | | |
920 | // v v | |
921 | // ( succ ) | |
922 | // | |
6522a427 | 923 | let else_ln = self.propagate_through_opt_expr(else_opt.as_deref(), succ); |
5869c6ff XL |
924 | let then_ln = self.propagate_through_expr(&then, succ); |
925 | let ln = self.live_node(expr.hir_id, expr.span); | |
926 | self.init_from_succ(ln, else_ln); | |
927 | self.merge_from_succ(ln, then_ln); | |
928 | self.propagate_through_expr(&cond, ln) | |
929 | } | |
223e47cc | 930 | |
dfeec247 | 931 | hir::ExprKind::Match(ref e, arms, _) => { |
0bf4aa26 XL |
932 | // |
933 | // (e) | |
934 | // | | |
935 | // v | |
936 | // (expr) | |
937 | // / | \ | |
938 | // | | | | |
939 | // v v v | |
940 | // (..arms..) | |
941 | // | | | | |
942 | // v v v | |
943 | // ( succ ) | |
944 | // | |
945 | // | |
946 | let ln = self.live_node(expr.hir_id, expr.span); | |
947 | self.init_empty(ln, succ); | |
0bf4aa26 XL |
948 | for arm in arms { |
949 | let body_succ = self.propagate_through_expr(&arm.body, succ); | |
950 | ||
fc512014 XL |
951 | let guard_succ = arm.guard.as_ref().map_or(body_succ, |g| match g { |
952 | hir::Guard::If(e) => self.propagate_through_expr(e, body_succ), | |
923072b8 FG |
953 | hir::Guard::IfLet(let_expr) => { |
954 | let let_bind = self.define_bindings_in_pat(let_expr.pat, body_succ); | |
955 | self.propagate_through_expr(let_expr.init, let_bind) | |
fc512014 XL |
956 | } |
957 | }); | |
e74abb32 | 958 | let arm_succ = self.define_bindings_in_pat(&arm.pat, guard_succ); |
fc512014 | 959 | self.merge_from_succ(ln, arm_succ); |
dfeec247 | 960 | } |
0bf4aa26 XL |
961 | self.propagate_through_expr(&e, ln) |
962 | } | |
223e47cc | 963 | |
0bf4aa26 | 964 | hir::ExprKind::Ret(ref o_e) => { |
1b1a35ee | 965 | // Ignore succ and subst exit_ln. |
6522a427 | 966 | self.propagate_through_opt_expr(o_e.as_deref(), self.exit_ln) |
0bf4aa26 | 967 | } |
223e47cc | 968 | |
0bf4aa26 XL |
969 | hir::ExprKind::Break(label, ref opt_expr) => { |
970 | // Find which label this break jumps to | |
971 | let target = match label.target_id { | |
532ac7d7 | 972 | Ok(hir_id) => self.break_ln.get(&hir_id), |
94b46f34 | 973 | Err(err) => span_bug!(expr.span, "loop scope error: {}", err), |
dfeec247 XL |
974 | } |
975 | .cloned(); | |
223e47cc | 976 | |
0bf4aa26 XL |
977 | // Now that we know the label we're going to, |
978 | // look it up in the break loop nodes table | |
8bb4bdeb | 979 | |
0bf4aa26 | 980 | match target { |
6522a427 | 981 | Some(b) => self.propagate_through_opt_expr(opt_expr.as_deref(), b), |
f035d41b | 982 | None => span_bug!(expr.span, "`break` to unknown label"), |
0bf4aa26 XL |
983 | } |
984 | } | |
223e47cc | 985 | |
0bf4aa26 XL |
986 | hir::ExprKind::Continue(label) => { |
987 | // Find which label this expr continues to | |
dfeec247 XL |
988 | let sc = label |
989 | .target_id | |
990 | .unwrap_or_else(|err| span_bug!(expr.span, "loop scope error: {}", err)); | |
223e47cc | 991 | |
0bf4aa26 XL |
992 | // Now that we know the label we're going to, |
993 | // look it up in the continue loop nodes table | |
dfeec247 XL |
994 | self.cont_ln |
995 | .get(&sc) | |
996 | .cloned() | |
997 | .unwrap_or_else(|| span_bug!(expr.span, "continue to unknown label")) | |
0bf4aa26 | 998 | } |
223e47cc | 999 | |
dfeec247 | 1000 | hir::ExprKind::Assign(ref l, ref r, _) => { |
2c00a5a8 XL |
1001 | // see comment on places in |
1002 | // propagate_through_place_components() | |
0bf4aa26 XL |
1003 | let succ = self.write_place(&l, succ, ACC_WRITE); |
1004 | let succ = self.propagate_through_place_components(&l, succ); | |
1005 | self.propagate_through_expr(&r, succ) | |
54a0048b | 1006 | } |
223e47cc | 1007 | |
0bf4aa26 XL |
1008 | hir::ExprKind::AssignOp(_, ref l, ref r) => { |
1009 | // an overloaded assign op is like a method call | |
3dfed10e | 1010 | if self.typeck_results.is_method_call(expr) { |
0bf4aa26 XL |
1011 | let succ = self.propagate_through_expr(&l, succ); |
1012 | self.propagate_through_expr(&r, succ) | |
1013 | } else { | |
1014 | // see comment on places in | |
1015 | // propagate_through_place_components() | |
dfeec247 | 1016 | let succ = self.write_place(&l, succ, ACC_WRITE | ACC_READ); |
0bf4aa26 XL |
1017 | let succ = self.propagate_through_expr(&r, succ); |
1018 | self.propagate_through_place_components(&l, succ) | |
1019 | } | |
1020 | } | |
223e47cc | 1021 | |
0bf4aa26 | 1022 | // Uninteresting cases: just propagate in rev exec order |
dfeec247 | 1023 | hir::ExprKind::Array(ref exprs) => self.propagate_through_exprs(exprs, succ), |
223e47cc | 1024 | |
0bf4aa26 | 1025 | hir::ExprKind::Struct(_, ref fields, ref with_expr) => { |
6522a427 | 1026 | let succ = self.propagate_through_opt_expr(with_expr.as_deref(), succ); |
dfeec247 XL |
1027 | fields |
1028 | .iter() | |
1029 | .rev() | |
1030 | .fold(succ, |succ, field| self.propagate_through_expr(&field.expr, succ)) | |
0bf4aa26 | 1031 | } |
223e47cc | 1032 | |
0bf4aa26 | 1033 | hir::ExprKind::Call(ref f, ref args) => { |
94222f64 | 1034 | let succ = self.check_is_ty_uninhabited(expr, succ); |
0bf4aa26 XL |
1035 | let succ = self.propagate_through_exprs(args, succ); |
1036 | self.propagate_through_expr(&f, succ) | |
1037 | } | |
223e47cc | 1038 | |
f2b60f7d | 1039 | hir::ExprKind::MethodCall(.., receiver, ref args, _) => { |
94222f64 | 1040 | let succ = self.check_is_ty_uninhabited(expr, succ); |
f2b60f7d FG |
1041 | let succ = self.propagate_through_exprs(args, succ); |
1042 | self.propagate_through_expr(receiver, succ) | |
0bf4aa26 | 1043 | } |
223e47cc | 1044 | |
dfeec247 | 1045 | hir::ExprKind::Tup(ref exprs) => self.propagate_through_exprs(exprs, succ), |
223e47cc | 1046 | |
0bf4aa26 XL |
1047 | hir::ExprKind::Binary(op, ref l, ref r) if op.node.is_lazy() => { |
1048 | let r_succ = self.propagate_through_expr(&r, succ); | |
223e47cc | 1049 | |
0bf4aa26 XL |
1050 | let ln = self.live_node(expr.hir_id, expr.span); |
1051 | self.init_from_succ(ln, succ); | |
fc512014 | 1052 | self.merge_from_succ(ln, r_succ); |
223e47cc | 1053 | |
0bf4aa26 XL |
1054 | self.propagate_through_expr(&l, ln) |
1055 | } | |
1a4d82fc | 1056 | |
dfeec247 | 1057 | hir::ExprKind::Index(ref l, ref r) | hir::ExprKind::Binary(_, ref l, ref r) => { |
0bf4aa26 XL |
1058 | let r_succ = self.propagate_through_expr(&r, succ); |
1059 | self.propagate_through_expr(&l, r_succ) | |
1060 | } | |
1061 | ||
dfeec247 XL |
1062 | hir::ExprKind::Box(ref e) |
1063 | | hir::ExprKind::AddrOf(_, _, ref e) | |
1064 | | hir::ExprKind::Cast(ref e, _) | |
1065 | | hir::ExprKind::Type(ref e, _) | |
1066 | | hir::ExprKind::DropTemps(ref e) | |
1067 | | hir::ExprKind::Unary(_, ref e) | |
dfeec247 | 1068 | | hir::ExprKind::Repeat(ref e, _) => self.propagate_through_expr(&e, succ), |
0bf4aa26 | 1069 | |
f9f354fc XL |
1070 | hir::ExprKind::InlineAsm(ref asm) => { |
1071 | // Handle non-returning asm | |
1072 | let mut succ = if asm.options.contains(InlineAsmOptions::NORETURN) { | |
1b1a35ee | 1073 | self.exit_ln |
f9f354fc XL |
1074 | } else { |
1075 | succ | |
1076 | }; | |
1077 | ||
1078 | // Do a first pass for writing outputs only | |
fc512014 | 1079 | for (op, _op_sp) in asm.operands.iter().rev() { |
f9f354fc XL |
1080 | match op { |
1081 | hir::InlineAsmOperand::In { .. } | |
1082 | | hir::InlineAsmOperand::Const { .. } | |
04454e1e FG |
1083 | | hir::InlineAsmOperand::SymFn { .. } |
1084 | | hir::InlineAsmOperand::SymStatic { .. } => {} | |
f9f354fc XL |
1085 | hir::InlineAsmOperand::Out { expr, .. } => { |
1086 | if let Some(expr) = expr { | |
1087 | succ = self.write_place(expr, succ, ACC_WRITE); | |
1088 | } | |
1089 | } | |
1090 | hir::InlineAsmOperand::InOut { expr, .. } => { | |
29967ef6 | 1091 | succ = self.write_place(expr, succ, ACC_READ | ACC_WRITE | ACC_USE); |
f9f354fc XL |
1092 | } |
1093 | hir::InlineAsmOperand::SplitInOut { out_expr, .. } => { | |
1094 | if let Some(expr) = out_expr { | |
1095 | succ = self.write_place(expr, succ, ACC_WRITE); | |
1096 | } | |
1097 | } | |
1098 | } | |
1099 | } | |
1100 | ||
1101 | // Then do a second pass for inputs | |
1102 | let mut succ = succ; | |
fc512014 | 1103 | for (op, _op_sp) in asm.operands.iter().rev() { |
f9f354fc | 1104 | match op { |
04454e1e | 1105 | hir::InlineAsmOperand::In { expr, .. } => { |
f9f354fc XL |
1106 | succ = self.propagate_through_expr(expr, succ) |
1107 | } | |
1108 | hir::InlineAsmOperand::Out { expr, .. } => { | |
1109 | if let Some(expr) = expr { | |
1110 | succ = self.propagate_through_place_components(expr, succ); | |
1111 | } | |
1112 | } | |
1113 | hir::InlineAsmOperand::InOut { expr, .. } => { | |
1114 | succ = self.propagate_through_place_components(expr, succ); | |
1115 | } | |
1116 | hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => { | |
1117 | if let Some(expr) = out_expr { | |
1118 | succ = self.propagate_through_place_components(expr, succ); | |
1119 | } | |
1120 | succ = self.propagate_through_expr(in_expr, succ); | |
1121 | } | |
04454e1e FG |
1122 | hir::InlineAsmOperand::Const { .. } |
1123 | | hir::InlineAsmOperand::SymFn { .. } | |
1124 | | hir::InlineAsmOperand::SymStatic { .. } => {} | |
f9f354fc XL |
1125 | } |
1126 | } | |
1127 | succ | |
1128 | } | |
1129 | ||
dfeec247 | 1130 | hir::ExprKind::Lit(..) |
29967ef6 | 1131 | | hir::ExprKind::ConstBlock(..) |
dfeec247 | 1132 | | hir::ExprKind::Err |
3dfed10e XL |
1133 | | hir::ExprKind::Path(hir::QPath::TypeRelative(..)) |
1134 | | hir::ExprKind::Path(hir::QPath::LangItem(..)) => succ, | |
223e47cc | 1135 | |
0bf4aa26 XL |
1136 | // Note that labels have been resolved, so we don't need to look |
1137 | // at the label ident | |
dfeec247 | 1138 | hir::ExprKind::Block(ref blk, _) => self.propagate_through_block(&blk, succ), |
223e47cc LB |
1139 | } |
1140 | } | |
1141 | ||
dfeec247 | 1142 | fn propagate_through_place_components(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode { |
2c00a5a8 | 1143 | // # Places |
223e47cc LB |
1144 | // |
1145 | // In general, the full flow graph structure for an | |
1146 | // assignment/move/etc can be handled in one of two ways, | |
1147 | // depending on whether what is being assigned is a "tracked | |
1148 | // value" or not. A tracked value is basically a local | |
1149 | // variable or argument. | |
1150 | // | |
1151 | // The two kinds of graphs are: | |
1152 | // | |
2c00a5a8 | 1153 | // Tracked place Untracked place |
223e47cc LB |
1154 | // ----------------------++----------------------- |
1155 | // || | |
1156 | // | || | | |
1157 | // v || v | |
1158 | // (rvalue) || (rvalue) | |
1159 | // | || | | |
1160 | // v || v | |
064997fb | 1161 | // (write of place) || (place components) |
223e47cc LB |
1162 | // | || | |
1163 | // v || v | |
1164 | // (succ) || (succ) | |
1165 | // || | |
1166 | // ----------------------++----------------------- | |
1167 | // | |
1168 | // I will cover the two cases in turn: | |
1169 | // | |
2c00a5a8 | 1170 | // # Tracked places |
223e47cc | 1171 | // |
6522a427 | 1172 | // A tracked place is a local variable/argument `x`. In |
223e47cc | 1173 | // these cases, the link_node where the write occurs is linked |
6522a427 EL |
1174 | // to node id of `x`. The `write_place()` routine generates |
1175 | // the contents of this node. There are no subcomponents to | |
223e47cc LB |
1176 | // consider. |
1177 | // | |
2c00a5a8 | 1178 | // # Non-tracked places |
223e47cc | 1179 | // |
6522a427 | 1180 | // These are places like `x[5]` or `x.f`. In that case, we |
223e47cc | 1181 | // basically ignore the value which is written to but generate |
6522a427 | 1182 | // reads for the components---`x` in these two examples. The |
223e47cc | 1183 | // components reads are generated by |
2c00a5a8 | 1184 | // `propagate_through_place_components()` (this fn). |
223e47cc | 1185 | // |
2c00a5a8 | 1186 | // # Illegal places |
223e47cc | 1187 | // |
2c00a5a8 | 1188 | // It is still possible to observe assignments to non-places; |
6522a427 | 1189 | // these errors are detected in the later pass borrowck. We |
223e47cc LB |
1190 | // just ignore such cases and treat them as reads. |
1191 | ||
e74abb32 | 1192 | match expr.kind { |
8faf50e0 XL |
1193 | hir::ExprKind::Path(_) => succ, |
1194 | hir::ExprKind::Field(ref e, _) => self.propagate_through_expr(&e, succ), | |
dfeec247 | 1195 | _ => self.propagate_through_expr(expr, succ), |
223e47cc LB |
1196 | } |
1197 | } | |
1198 | ||
2c00a5a8 | 1199 | // see comment on propagate_through_place() |
dfeec247 | 1200 | fn write_place(&mut self, expr: &Expr<'_>, succ: LiveNode, acc: u32) -> LiveNode { |
e74abb32 | 1201 | match expr.kind { |
0bf4aa26 XL |
1202 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { |
1203 | self.access_path(expr.hir_id, path, succ, acc) | |
1204 | } | |
223e47cc | 1205 | |
0bf4aa26 | 1206 | // We do not track other places, so just propagate through |
6522a427 | 1207 | // to their subcomponents. Also, it may happen that |
0bf4aa26 XL |
1208 | // non-places occur here, because those are detected in the |
1209 | // later pass borrowck. | |
dfeec247 | 1210 | _ => succ, |
223e47cc LB |
1211 | } |
1212 | } | |
1213 | ||
dfeec247 XL |
1214 | fn access_var( |
1215 | &mut self, | |
1216 | hir_id: HirId, | |
1217 | var_hid: HirId, | |
1218 | succ: LiveNode, | |
1219 | acc: u32, | |
1220 | span: Span, | |
1221 | ) -> LiveNode { | |
94b46f34 | 1222 | let ln = self.live_node(hir_id, span); |
ea8adc8c XL |
1223 | if acc != 0 { |
1224 | self.init_from_succ(ln, succ); | |
94b46f34 | 1225 | let var = self.variable(var_hid, span); |
ea8adc8c XL |
1226 | self.acc(ln, var, acc); |
1227 | } | |
1228 | ln | |
1229 | } | |
1230 | ||
dfeec247 XL |
1231 | fn access_path( |
1232 | &mut self, | |
1233 | hir_id: HirId, | |
1234 | path: &hir::Path<'_>, | |
1235 | succ: LiveNode, | |
1236 | acc: u32, | |
1237 | ) -> LiveNode { | |
48663c56 | 1238 | match path.res { |
94222f64 | 1239 | Res::Local(hid) => self.access_var(hir_id, hid, succ, acc, path.span), |
dfeec247 | 1240 | _ => succ, |
223e47cc LB |
1241 | } |
1242 | } | |
1243 | ||
416331ca XL |
1244 | fn propagate_through_loop( |
1245 | &mut self, | |
dfeec247 XL |
1246 | expr: &Expr<'_>, |
1247 | body: &hir::Block<'_>, | |
1248 | succ: LiveNode, | |
416331ca | 1249 | ) -> LiveNode { |
223e47cc | 1250 | /* |
223e47cc LB |
1251 | We model control flow like this: |
1252 | ||
416331ca XL |
1253 | (expr) <-+ |
1254 | | | | |
1255 | v | | |
1256 | (body) --+ | |
223e47cc | 1257 | |
416331ca XL |
1258 | Note that a `continue` expression targeting the `loop` will have a successor of `expr`. |
1259 | Meanwhile, a `break` expression will have a successor of `succ`. | |
223e47cc LB |
1260 | */ |
1261 | ||
223e47cc | 1262 | // first iteration: |
94b46f34 | 1263 | let ln = self.live_node(expr.hir_id, expr.span); |
223e47cc | 1264 | self.init_empty(ln, succ); |
ba9703b0 | 1265 | debug!("propagate_through_loop: using id for loop body {} {:?}", expr.hir_id, body); |
9fa01778 | 1266 | |
532ac7d7 | 1267 | self.break_ln.insert(expr.hir_id, succ); |
cc61c64b | 1268 | |
416331ca | 1269 | self.cont_ln.insert(expr.hir_id, ln); |
9fa01778 | 1270 | |
416331ca | 1271 | let body_ln = self.propagate_through_block(body, ln); |
223e47cc LB |
1272 | |
1273 | // repeat until fixed point is reached: | |
fc512014 | 1274 | while self.merge_from_succ(ln, body_ln) { |
416331ca | 1275 | assert_eq!(body_ln, self.propagate_through_block(body, ln)); |
223e47cc LB |
1276 | } |
1277 | ||
416331ca | 1278 | ln |
223e47cc | 1279 | } |
94222f64 XL |
1280 | |
1281 | fn check_is_ty_uninhabited(&mut self, expr: &Expr<'_>, succ: LiveNode) -> LiveNode { | |
1282 | let ty = self.typeck_results.expr_ty(expr); | |
1283 | let m = self.ir.tcx.parent_module(expr.hir_id).to_def_id(); | |
6522a427 EL |
1284 | if ty.is_inhabited_from(self.ir.tcx, m, self.param_env) { |
1285 | return succ; | |
94222f64 | 1286 | } |
6522a427 EL |
1287 | match self.ir.lnks[succ] { |
1288 | LiveNodeKind::ExprNode(succ_span, succ_id) => { | |
1289 | self.warn_about_unreachable(expr.span, ty, succ_span, succ_id, "expression"); | |
1290 | } | |
1291 | LiveNodeKind::VarDefNode(succ_span, succ_id) => { | |
1292 | self.warn_about_unreachable(expr.span, ty, succ_span, succ_id, "definition"); | |
1293 | } | |
1294 | _ => {} | |
1295 | }; | |
1296 | self.exit_ln | |
94222f64 XL |
1297 | } |
1298 | ||
1299 | fn warn_about_unreachable( | |
1300 | &mut self, | |
1301 | orig_span: Span, | |
1302 | orig_ty: Ty<'tcx>, | |
1303 | expr_span: Span, | |
1304 | expr_id: HirId, | |
1305 | descr: &str, | |
1306 | ) { | |
1307 | if !orig_ty.is_never() { | |
1308 | // Unreachable code warnings are already emitted during type checking. | |
1309 | // However, during type checking, full type information is being | |
1310 | // calculated but not yet available, so the check for diverging | |
1311 | // expressions due to uninhabited result types is pretty crude and | |
1312 | // only checks whether ty.is_never(). Here, we have full type | |
1313 | // information available and can issue warnings for less obviously | |
1314 | // uninhabited types (e.g. empty enums). The check above is used so | |
1315 | // that we do not emit the same warning twice if the uninhabited type | |
1316 | // is indeed `!`. | |
1317 | ||
2b03887a | 1318 | let msg = format!("unreachable {}", descr); |
94222f64 XL |
1319 | self.ir.tcx.struct_span_lint_hir( |
1320 | lint::builtin::UNREACHABLE_CODE, | |
1321 | expr_id, | |
1322 | expr_span, | |
2b03887a FG |
1323 | &msg, |
1324 | |diag| { | |
1325 | diag.span_label(expr_span, &msg) | |
94222f64 XL |
1326 | .span_label(orig_span, "any code following this expression is unreachable") |
1327 | .span_note( | |
1328 | orig_span, | |
1329 | &format!( | |
1330 | "this expression has type `{}`, which is uninhabited", | |
1331 | orig_ty | |
1332 | ), | |
1333 | ) | |
94222f64 XL |
1334 | }, |
1335 | ); | |
1336 | } | |
1337 | } | |
223e47cc LB |
1338 | } |
1339 | ||
1340 | // _______________________________________________________________________ | |
1341 | // Checking for error conditions | |
1342 | ||
32a655c1 | 1343 | impl<'a, 'tcx> Visitor<'tcx> for Liveness<'a, 'tcx> { |
dfeec247 | 1344 | fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) { |
f2b60f7d | 1345 | self.check_unused_vars_in_pat(&local.pat, None, None, |spans, hir_id, ln, var| { |
e74abb32 XL |
1346 | if local.init.is_some() { |
1347 | self.warn_about_dead_assign(spans, hir_id, ln, var); | |
1348 | } | |
1349 | }); | |
32a655c1 | 1350 | |
e74abb32 | 1351 | intravisit::walk_local(self, local); |
223e47cc LB |
1352 | } |
1353 | ||
dfeec247 | 1354 | fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) { |
e74abb32 | 1355 | check_expr(self, ex); |
94222f64 | 1356 | intravisit::walk_expr(self, ex); |
9fa01778 XL |
1357 | } |
1358 | ||
dfeec247 | 1359 | fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) { |
f2b60f7d | 1360 | self.check_unused_vars_in_pat(&arm.pat, None, None, |_, _, _, _| {}); |
e74abb32 | 1361 | intravisit::walk_arm(self, arm); |
9fa01778 | 1362 | } |
223e47cc LB |
1363 | } |
1364 | ||
dfeec247 | 1365 | fn check_expr<'tcx>(this: &mut Liveness<'_, 'tcx>, expr: &'tcx Expr<'tcx>) { |
e74abb32 | 1366 | match expr.kind { |
dfeec247 | 1367 | hir::ExprKind::Assign(ref l, ..) => { |
2c00a5a8 | 1368 | this.check_place(&l); |
54a0048b | 1369 | } |
223e47cc | 1370 | |
0bf4aa26 | 1371 | hir::ExprKind::AssignOp(_, ref l, _) => { |
3dfed10e | 1372 | if !this.typeck_results.is_method_call(expr) { |
0bf4aa26 XL |
1373 | this.check_place(&l); |
1374 | } | |
223e47cc LB |
1375 | } |
1376 | ||
f9f354fc | 1377 | hir::ExprKind::InlineAsm(ref asm) => { |
fc512014 | 1378 | for (op, _op_sp) in asm.operands { |
f9f354fc XL |
1379 | match op { |
1380 | hir::InlineAsmOperand::Out { expr, .. } => { | |
1381 | if let Some(expr) = expr { | |
1382 | this.check_place(expr); | |
1383 | } | |
1384 | } | |
1385 | hir::InlineAsmOperand::InOut { expr, .. } => { | |
1386 | this.check_place(expr); | |
1387 | } | |
1388 | hir::InlineAsmOperand::SplitInOut { out_expr, .. } => { | |
1389 | if let Some(out_expr) = out_expr { | |
1390 | this.check_place(out_expr); | |
1391 | } | |
1392 | } | |
1393 | _ => {} | |
1394 | } | |
1395 | } | |
1396 | } | |
1397 | ||
a2a8927a | 1398 | hir::ExprKind::Let(let_expr) => { |
f2b60f7d | 1399 | this.check_unused_vars_in_pat(let_expr.pat, None, None, |_, _, _, _| {}); |
94222f64 XL |
1400 | } |
1401 | ||
0bf4aa26 | 1402 | // no correctness conditions related to liveness |
dfeec247 XL |
1403 | hir::ExprKind::Call(..) |
1404 | | hir::ExprKind::MethodCall(..) | |
1405 | | hir::ExprKind::Match(..) | |
1406 | | hir::ExprKind::Loop(..) | |
1407 | | hir::ExprKind::Index(..) | |
1408 | | hir::ExprKind::Field(..) | |
1409 | | hir::ExprKind::Array(..) | |
1410 | | hir::ExprKind::Tup(..) | |
1411 | | hir::ExprKind::Binary(..) | |
1412 | | hir::ExprKind::Cast(..) | |
5869c6ff | 1413 | | hir::ExprKind::If(..) |
dfeec247 XL |
1414 | | hir::ExprKind::DropTemps(..) |
1415 | | hir::ExprKind::Unary(..) | |
1416 | | hir::ExprKind::Ret(..) | |
1417 | | hir::ExprKind::Break(..) | |
1418 | | hir::ExprKind::Continue(..) | |
1419 | | hir::ExprKind::Lit(_) | |
29967ef6 | 1420 | | hir::ExprKind::ConstBlock(..) |
dfeec247 XL |
1421 | | hir::ExprKind::Block(..) |
1422 | | hir::ExprKind::AddrOf(..) | |
1423 | | hir::ExprKind::Struct(..) | |
1424 | | hir::ExprKind::Repeat(..) | |
923072b8 | 1425 | | hir::ExprKind::Closure { .. } |
dfeec247 XL |
1426 | | hir::ExprKind::Path(_) |
1427 | | hir::ExprKind::Yield(..) | |
1428 | | hir::ExprKind::Box(..) | |
1429 | | hir::ExprKind::Type(..) | |
1430 | | hir::ExprKind::Err => {} | |
223e47cc LB |
1431 | } |
1432 | } | |
1433 | ||
e74abb32 | 1434 | impl<'tcx> Liveness<'_, 'tcx> { |
dfeec247 | 1435 | fn check_place(&mut self, expr: &'tcx Expr<'tcx>) { |
e74abb32 | 1436 | match expr.kind { |
8faf50e0 | 1437 | hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => { |
48663c56 | 1438 | if let Res::Local(var_hid) = path.res { |
f9f354fc XL |
1439 | // Assignment to an immutable variable or argument: only legal |
1440 | // if there is no later assignment. If this local is actually | |
1441 | // mutable, then check for a reassignment to flag the mutability | |
1442 | // as being used. | |
1443 | let ln = self.live_node(expr.hir_id, expr.span); | |
1444 | let var = self.variable(var_hid, expr.span); | |
1445 | self.warn_about_dead_assign(vec![expr.span], expr.hir_id, ln, var); | |
223e47cc | 1446 | } |
223e47cc | 1447 | } |
1a4d82fc | 1448 | _ => { |
2c00a5a8 | 1449 | // For other kinds of places, no checks are required, |
1a4d82fc | 1450 | // and any embedded expressions are actually rvalues |
92a42be0 | 1451 | intravisit::walk_expr(self, expr); |
1a4d82fc | 1452 | } |
223e47cc LB |
1453 | } |
1454 | } | |
1455 | ||
1a4d82fc | 1456 | fn should_warn(&self, var: Variable) -> Option<String> { |
223e47cc | 1457 | let name = self.ir.variable_name(var); |
5869c6ff | 1458 | if name == kw::Empty { |
1b1a35ee XL |
1459 | return None; |
1460 | } | |
a2a8927a | 1461 | let name = name.as_str(); |
1b1a35ee XL |
1462 | if name.as_bytes()[0] == b'_' { |
1463 | return None; | |
1464 | } | |
1465 | Some(name.to_owned()) | |
223e47cc LB |
1466 | } |
1467 | ||
f9f354fc | 1468 | fn warn_about_unused_upvars(&self, entry_ln: LiveNode) { |
5e7ed085 FG |
1469 | let Some(closure_min_captures) = self.closure_min_captures else { |
1470 | return; | |
f9f354fc | 1471 | }; |
fc512014 | 1472 | |
6a06907d XL |
1473 | // If closure_min_captures is Some(), upvars must be Some() too. |
1474 | for (&var_hir_id, min_capture_list) in closure_min_captures { | |
1475 | for captured_place in min_capture_list { | |
1476 | match captured_place.info.capture_kind { | |
5099ac24 | 1477 | ty::UpvarCapture::ByValue => {} |
6a06907d XL |
1478 | ty::UpvarCapture::ByRef(..) => continue, |
1479 | }; | |
1480 | let span = captured_place.get_capture_kind_span(self.ir.tcx); | |
1481 | let var = self.variable(var_hir_id, span); | |
1482 | if self.used_on_entry(entry_ln, var) { | |
1483 | if !self.live_on_entry(entry_ln, var) { | |
1484 | if let Some(name) = self.should_warn(var) { | |
1485 | self.ir.tcx.struct_span_lint_hir( | |
1486 | lint::builtin::UNUSED_ASSIGNMENTS, | |
1487 | var_hir_id, | |
1488 | vec![span], | |
2b03887a FG |
1489 | format!("value captured by `{}` is never read", name), |
1490 | |lint| lint.help("did you mean to capture by reference instead?"), | |
6a06907d XL |
1491 | ); |
1492 | } | |
1493 | } | |
1494 | } else { | |
f9f354fc XL |
1495 | if let Some(name) = self.should_warn(var) { |
1496 | self.ir.tcx.struct_span_lint_hir( | |
6a06907d | 1497 | lint::builtin::UNUSED_VARIABLES, |
f9f354fc | 1498 | var_hir_id, |
6a06907d | 1499 | vec![span], |
2b03887a FG |
1500 | format!("unused variable: `{}`", name), |
1501 | |lint| lint.help("did you mean to capture by reference instead?"), | |
f9f354fc XL |
1502 | ); |
1503 | } | |
1504 | } | |
f9f354fc XL |
1505 | } |
1506 | } | |
1507 | } | |
1508 | ||
dfeec247 XL |
1509 | fn warn_about_unused_args(&self, body: &hir::Body<'_>, entry_ln: LiveNode) { |
1510 | for p in body.params { | |
f2b60f7d FG |
1511 | self.check_unused_vars_in_pat( |
1512 | &p.pat, | |
1513 | Some(entry_ln), | |
1514 | Some(body), | |
1515 | |spans, hir_id, ln, var| { | |
1516 | if !self.live_on_entry(ln, var) { | |
1517 | self.report_unused_assign(hir_id, spans, var, |name| { | |
1518 | format!("value passed to `{}` is never read", name) | |
1519 | }); | |
1520 | } | |
1521 | }, | |
1522 | ); | |
223e47cc LB |
1523 | } |
1524 | } | |
1525 | ||
e74abb32 XL |
1526 | fn check_unused_vars_in_pat( |
1527 | &self, | |
dfeec247 | 1528 | pat: &hir::Pat<'_>, |
e74abb32 | 1529 | entry_ln: Option<LiveNode>, |
f2b60f7d | 1530 | opt_body: Option<&hir::Body<'_>>, |
e74abb32 XL |
1531 | on_used_on_entry: impl Fn(Vec<Span>, HirId, LiveNode, Variable), |
1532 | ) { | |
1533 | // In an or-pattern, only consider the variable; any later patterns must have the same | |
1534 | // bindings, and we also consider the first pattern to be the "authoritative" set of ids. | |
ba9703b0 | 1535 | // However, we should take the ids and spans of variables with the same name from the later |
e74abb32 | 1536 | // patterns so the suggestions to prefix with underscores will apply to those too. |
6a06907d XL |
1537 | let mut vars: FxIndexMap<Symbol, (LiveNode, Variable, Vec<(HirId, Span, Span)>)> = |
1538 | <_>::default(); | |
e74abb32 XL |
1539 | |
1540 | pat.each_binding(|_, hir_id, pat_sp, ident| { | |
1541 | let ln = entry_ln.unwrap_or_else(|| self.live_node(hir_id, pat_sp)); | |
1542 | let var = self.variable(hir_id, ident.span); | |
6a06907d | 1543 | let id_and_sp = (hir_id, pat_sp, ident.span); |
e74abb32 | 1544 | vars.entry(self.ir.variable_name(var)) |
ba9703b0 XL |
1545 | .and_modify(|(.., hir_ids_and_spans)| hir_ids_and_spans.push(id_and_sp)) |
1546 | .or_insert_with(|| (ln, var, vec![id_and_sp])); | |
e74abb32 XL |
1547 | }); |
1548 | ||
6522a427 EL |
1549 | let can_remove = match pat.kind { |
1550 | hir::PatKind::Struct(_, fields, true) => { | |
1551 | // if all fields are shorthand, remove the struct field, otherwise, mark with _ as prefix | |
1552 | fields.iter().all(|f| f.is_shorthand) | |
1553 | } | |
1554 | _ => false, | |
1555 | }; | |
f2b60f7d | 1556 | |
ba9703b0 | 1557 | for (_, (ln, var, hir_ids_and_spans)) in vars { |
e74abb32 | 1558 | if self.used_on_entry(ln, var) { |
ba9703b0 | 1559 | let id = hir_ids_and_spans[0].0; |
6a06907d XL |
1560 | let spans = |
1561 | hir_ids_and_spans.into_iter().map(|(_, _, ident_span)| ident_span).collect(); | |
e74abb32 XL |
1562 | on_used_on_entry(spans, id, ln, var); |
1563 | } else { | |
f2b60f7d | 1564 | self.report_unused(hir_ids_and_spans, ln, var, can_remove, pat, opt_body); |
223e47cc | 1565 | } |
e74abb32 | 1566 | } |
223e47cc LB |
1567 | } |
1568 | ||
f2b60f7d | 1569 | #[instrument(skip(self), level = "INFO")] |
6a06907d XL |
1570 | fn report_unused( |
1571 | &self, | |
1572 | hir_ids_and_spans: Vec<(HirId, Span, Span)>, | |
1573 | ln: LiveNode, | |
1574 | var: Variable, | |
f2b60f7d FG |
1575 | can_remove: bool, |
1576 | pat: &hir::Pat<'_>, | |
1577 | opt_body: Option<&hir::Body<'_>>, | |
6a06907d | 1578 | ) { |
ba9703b0 XL |
1579 | let first_hir_id = hir_ids_and_spans[0].0; |
1580 | ||
e74abb32 XL |
1581 | if let Some(name) = self.should_warn(var).filter(|name| name != "self") { |
1582 | // annoying: for parameters in funcs like `fn(x: i32) | |
1583 | // {ret}`, there is only one node, so asking about | |
1584 | // assigned_on_exit() is not meaningful. | |
dfeec247 | 1585 | let is_assigned = |
fc512014 | 1586 | if ln == self.exit_ln { false } else { self.assigned_on_exit(ln, var) }; |
223e47cc | 1587 | |
e74abb32 | 1588 | if is_assigned { |
74b04a01 XL |
1589 | self.ir.tcx.struct_span_lint_hir( |
1590 | lint::builtin::UNUSED_VARIABLES, | |
ba9703b0 | 1591 | first_hir_id, |
6a06907d XL |
1592 | hir_ids_and_spans |
1593 | .into_iter() | |
1594 | .map(|(_, _, ident_span)| ident_span) | |
1595 | .collect::<Vec<_>>(), | |
2b03887a FG |
1596 | format!("variable `{}` is assigned to, but never used", name), |
1597 | |lint| lint.note(&format!("consider using `_{}` instead", name)), | |
74b04a01 | 1598 | ) |
f2b60f7d FG |
1599 | } else if can_remove { |
1600 | self.ir.tcx.struct_span_lint_hir( | |
1601 | lint::builtin::UNUSED_VARIABLES, | |
1602 | first_hir_id, | |
1603 | hir_ids_and_spans.iter().map(|(_, pat_span, _)| *pat_span).collect::<Vec<_>>(), | |
2b03887a | 1604 | format!("unused variable: `{}`", name), |
f2b60f7d | 1605 | |lint| { |
2b03887a | 1606 | lint.multipart_suggestion( |
f2b60f7d FG |
1607 | "try removing the field", |
1608 | hir_ids_and_spans | |
1609 | .iter() | |
1610 | .map(|(_, pat_span, _)| { | |
1611 | let span = self | |
1612 | .ir | |
1613 | .tcx | |
1614 | .sess | |
1615 | .source_map() | |
1616 | .span_extend_to_next_char(*pat_span, ',', true); | |
1617 | (span.with_hi(BytePos(span.hi().0 + 1)), String::new()) | |
1618 | }) | |
1619 | .collect(), | |
1620 | Applicability::MachineApplicable, | |
2b03887a | 1621 | ) |
f2b60f7d FG |
1622 | }, |
1623 | ); | |
e74abb32 | 1624 | } else { |
6a06907d XL |
1625 | let (shorthands, non_shorthands): (Vec<_>, Vec<_>) = |
1626 | hir_ids_and_spans.iter().copied().partition(|(hir_id, _, ident_span)| { | |
1627 | let var = self.variable(*hir_id, *ident_span); | |
1628 | self.ir.variable_is_shorthand(var) | |
1629 | }); | |
ba9703b0 | 1630 | |
6a06907d XL |
1631 | // If we have both shorthand and non-shorthand, prefer the "try ignoring |
1632 | // the field" message, and suggest `_` for the non-shorthands. If we only | |
1633 | // have non-shorthand, then prefix with an underscore instead. | |
1634 | if !shorthands.is_empty() { | |
1635 | let shorthands = shorthands | |
1636 | .into_iter() | |
1637 | .map(|(_, pat_span, _)| (pat_span, format!("{}: _", name))) | |
1638 | .chain( | |
1639 | non_shorthands | |
1640 | .into_iter() | |
1641 | .map(|(_, pat_span, _)| (pat_span, "_".to_string())), | |
1642 | ) | |
1643 | .collect::<Vec<_>>(); | |
1644 | ||
1645 | self.ir.tcx.struct_span_lint_hir( | |
1646 | lint::builtin::UNUSED_VARIABLES, | |
1647 | first_hir_id, | |
1648 | hir_ids_and_spans | |
1649 | .iter() | |
1650 | .map(|(_, pat_span, _)| *pat_span) | |
1651 | .collect::<Vec<_>>(), | |
2b03887a | 1652 | format!("unused variable: `{}`", name), |
6a06907d | 1653 | |lint| { |
2b03887a | 1654 | lint.multipart_suggestion( |
ba9703b0 XL |
1655 | "try ignoring the field", |
1656 | shorthands, | |
1657 | Applicability::MachineApplicable, | |
2b03887a | 1658 | ) |
6a06907d XL |
1659 | }, |
1660 | ); | |
1661 | } else { | |
1662 | let non_shorthands = non_shorthands | |
1663 | .into_iter() | |
1664 | .map(|(_, _, ident_span)| (ident_span, format!("_{}", name))) | |
1665 | .collect::<Vec<_>>(); | |
1666 | ||
1667 | self.ir.tcx.struct_span_lint_hir( | |
1668 | lint::builtin::UNUSED_VARIABLES, | |
1669 | first_hir_id, | |
1670 | hir_ids_and_spans | |
1671 | .iter() | |
1672 | .map(|(_, _, ident_span)| *ident_span) | |
1673 | .collect::<Vec<_>>(), | |
2b03887a | 1674 | format!("unused variable: `{}`", name), |
6a06907d | 1675 | |lint| { |
2b03887a FG |
1676 | if self.has_added_lit_match_name_span(&name, opt_body, lint) { |
1677 | lint.span_label(pat.span, "unused variable"); | |
f2b60f7d | 1678 | } |
2b03887a | 1679 | lint.multipart_suggestion( |
ba9703b0 | 1680 | "if this is intentional, prefix it with an underscore", |
6a06907d | 1681 | non_shorthands, |
74b04a01 | 1682 | Applicability::MachineApplicable, |
2b03887a | 1683 | ) |
6a06907d XL |
1684 | }, |
1685 | ); | |
1686 | } | |
223e47cc | 1687 | } |
223e47cc | 1688 | } |
223e47cc LB |
1689 | } |
1690 | ||
f2b60f7d FG |
1691 | fn has_added_lit_match_name_span( |
1692 | &self, | |
1693 | name: &str, | |
1694 | opt_body: Option<&hir::Body<'_>>, | |
6522a427 | 1695 | err: &mut Diagnostic, |
f2b60f7d FG |
1696 | ) -> bool { |
1697 | let mut has_litstring = false; | |
1698 | let Some(opt_body) = opt_body else {return false;}; | |
1699 | let mut visitor = CollectLitsVisitor { lit_exprs: vec![] }; | |
1700 | intravisit::walk_body(&mut visitor, opt_body); | |
1701 | for lit_expr in visitor.lit_exprs { | |
1702 | let hir::ExprKind::Lit(litx) = &lit_expr.kind else { continue }; | |
1703 | let rustc_ast::LitKind::Str(syb, _) = litx.node else{ continue; }; | |
1704 | let name_str: &str = syb.as_str(); | |
1705 | let mut name_pa = String::from("{"); | |
1706 | name_pa.push_str(&name); | |
1707 | name_pa.push('}'); | |
1708 | if name_str.contains(&name_pa) { | |
1709 | err.span_label( | |
1710 | lit_expr.span, | |
1711 | "you might have meant to use string interpolation in this string literal", | |
1712 | ); | |
1713 | err.multipart_suggestion( | |
1714 | "string interpolation only works in `format!` invocations", | |
1715 | vec![ | |
1716 | (lit_expr.span.shrink_to_lo(), "format!(".to_string()), | |
1717 | (lit_expr.span.shrink_to_hi(), ")".to_string()), | |
1718 | ], | |
1719 | Applicability::MachineApplicable, | |
1720 | ); | |
1721 | has_litstring = true; | |
1722 | } | |
1723 | } | |
1724 | has_litstring | |
1725 | } | |
1726 | ||
e74abb32 | 1727 | fn warn_about_dead_assign(&self, spans: Vec<Span>, hir_id: HirId, ln: LiveNode, var: Variable) { |
fc512014 | 1728 | if !self.live_on_exit(ln, var) { |
cdc7bbd5 | 1729 | self.report_unused_assign(hir_id, spans, var, |name| { |
f9f354fc XL |
1730 | format!("value assigned to `{}` is never read", name) |
1731 | }); | |
92a42be0 SL |
1732 | } |
1733 | } | |
1734 | ||
cdc7bbd5 | 1735 | fn report_unused_assign( |
f9f354fc XL |
1736 | &self, |
1737 | hir_id: HirId, | |
1738 | spans: Vec<Span>, | |
1739 | var: Variable, | |
1740 | message: impl Fn(&str) -> String, | |
1741 | ) { | |
92a42be0 | 1742 | if let Some(name) = self.should_warn(var) { |
f9f354fc XL |
1743 | self.ir.tcx.struct_span_lint_hir( |
1744 | lint::builtin::UNUSED_ASSIGNMENTS, | |
1745 | hir_id, | |
1746 | spans, | |
2b03887a FG |
1747 | message(&name), |
1748 | |lint| lint.help("maybe it is overwritten before being read?"), | |
f9f354fc | 1749 | ) |
223e47cc LB |
1750 | } |
1751 | } | |
92a42be0 | 1752 | } |