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94222f64 XL |
1 | use crate::{ImplTraitContext, ImplTraitPosition, LoweringContext}; |
2 | use rustc_ast::{AttrVec, Block, BlockCheckMode, Expr, Local, LocalKind, Stmt, StmtKind}; | |
3 | use rustc_hir as hir; | |
4 | use rustc_session::parse::feature_err; | |
5 | use rustc_span::symbol::Ident; | |
6 | use rustc_span::{sym, DesugaringKind}; | |
7 | ||
8 | use smallvec::SmallVec; | |
9 | ||
10 | impl<'a, 'hir> LoweringContext<'a, 'hir> { | |
11 | pub(super) fn lower_block( | |
12 | &mut self, | |
13 | b: &Block, | |
14 | targeted_by_break: bool, | |
15 | ) -> &'hir hir::Block<'hir> { | |
16 | self.arena.alloc(self.lower_block_noalloc(b, targeted_by_break)) | |
17 | } | |
18 | ||
19 | pub(super) fn lower_block_noalloc( | |
20 | &mut self, | |
21 | b: &Block, | |
22 | targeted_by_break: bool, | |
23 | ) -> hir::Block<'hir> { | |
24 | let (stmts, expr) = self.lower_stmts(&b.stmts); | |
25 | let rules = self.lower_block_check_mode(&b.rules); | |
26 | let hir_id = self.lower_node_id(b.id); | |
27 | hir::Block { hir_id, stmts, expr, rules, span: self.lower_span(b.span), targeted_by_break } | |
28 | } | |
29 | ||
30 | fn lower_stmts( | |
31 | &mut self, | |
32 | mut ast_stmts: &[Stmt], | |
33 | ) -> (&'hir [hir::Stmt<'hir>], Option<&'hir hir::Expr<'hir>>) { | |
34 | let mut stmts = SmallVec::<[hir::Stmt<'hir>; 8]>::new(); | |
35 | let mut expr = None; | |
36 | while let [s, tail @ ..] = ast_stmts { | |
37 | match s.kind { | |
38 | StmtKind::Local(ref local) => { | |
39 | let hir_id = self.lower_node_id(s.id); | |
40 | match &local.kind { | |
41 | LocalKind::InitElse(init, els) => { | |
42 | let (s, e) = self.lower_let_else(hir_id, local, init, els, tail); | |
43 | stmts.push(s); | |
44 | expr = Some(e); | |
45 | // remaining statements are in let-else expression | |
46 | break; | |
47 | } | |
48 | _ => { | |
49 | let local = self.lower_local(local); | |
50 | self.alias_attrs(hir_id, local.hir_id); | |
51 | let kind = hir::StmtKind::Local(local); | |
52 | let span = self.lower_span(s.span); | |
53 | stmts.push(hir::Stmt { hir_id, kind, span }); | |
54 | } | |
55 | } | |
56 | } | |
57 | StmtKind::Item(ref it) => { | |
c295e0f8 | 58 | stmts.extend(self.lower_item_ref(it).into_iter().enumerate().map( |
94222f64 XL |
59 | |(i, item_id)| { |
60 | let hir_id = match i { | |
61 | 0 => self.lower_node_id(s.id), | |
62 | _ => self.next_id(), | |
63 | }; | |
64 | let kind = hir::StmtKind::Item(item_id); | |
65 | let span = self.lower_span(s.span); | |
66 | hir::Stmt { hir_id, kind, span } | |
67 | }, | |
68 | )); | |
69 | } | |
70 | StmtKind::Expr(ref e) => { | |
71 | let e = self.lower_expr(e); | |
72 | if tail.is_empty() { | |
73 | expr = Some(e); | |
74 | } else { | |
75 | let hir_id = self.lower_node_id(s.id); | |
76 | self.alias_attrs(hir_id, e.hir_id); | |
77 | let kind = hir::StmtKind::Expr(e); | |
78 | let span = self.lower_span(s.span); | |
79 | stmts.push(hir::Stmt { hir_id, kind, span }); | |
80 | } | |
81 | } | |
82 | StmtKind::Semi(ref e) => { | |
83 | let e = self.lower_expr(e); | |
84 | let hir_id = self.lower_node_id(s.id); | |
85 | self.alias_attrs(hir_id, e.hir_id); | |
86 | let kind = hir::StmtKind::Semi(e); | |
87 | let span = self.lower_span(s.span); | |
88 | stmts.push(hir::Stmt { hir_id, kind, span }); | |
89 | } | |
90 | StmtKind::Empty => {} | |
91 | StmtKind::MacCall(..) => panic!("shouldn't exist here"), | |
92 | } | |
93 | ast_stmts = &ast_stmts[1..]; | |
94 | } | |
95 | (self.arena.alloc_from_iter(stmts), expr) | |
96 | } | |
97 | ||
98 | fn lower_local(&mut self, l: &Local) -> &'hir hir::Local<'hir> { | |
99 | let ty = l | |
100 | .ty | |
101 | .as_ref() | |
102 | .map(|t| self.lower_ty(t, ImplTraitContext::Disallowed(ImplTraitPosition::Binding))); | |
103 | let init = l.kind.init().map(|init| self.lower_expr(init)); | |
104 | let hir_id = self.lower_node_id(l.id); | |
105 | let pat = self.lower_pat(&l.pat); | |
106 | let span = self.lower_span(l.span); | |
107 | let source = hir::LocalSource::Normal; | |
108 | self.lower_attrs(hir_id, &l.attrs); | |
109 | self.arena.alloc(hir::Local { hir_id, ty, pat, init, span, source }) | |
110 | } | |
111 | ||
112 | fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode { | |
113 | match *b { | |
114 | BlockCheckMode::Default => hir::BlockCheckMode::DefaultBlock, | |
115 | BlockCheckMode::Unsafe(u) => { | |
116 | hir::BlockCheckMode::UnsafeBlock(self.lower_unsafe_source(u)) | |
117 | } | |
118 | } | |
119 | } | |
120 | ||
121 | fn lower_let_else( | |
122 | &mut self, | |
123 | stmt_hir_id: hir::HirId, | |
124 | local: &Local, | |
125 | init: &Expr, | |
126 | els: &Block, | |
127 | tail: &[Stmt], | |
128 | ) -> (hir::Stmt<'hir>, &'hir hir::Expr<'hir>) { | |
129 | let ty = local | |
130 | .ty | |
131 | .as_ref() | |
132 | .map(|t| self.lower_ty(t, ImplTraitContext::Disallowed(ImplTraitPosition::Binding))); | |
133 | let span = self.lower_span(local.span); | |
134 | let span = self.mark_span_with_reason(DesugaringKind::LetElse, span, None); | |
135 | let init = Some(self.lower_expr(init)); | |
136 | let val = Ident::with_dummy_span(sym::val); | |
137 | let (pat, val_id) = | |
138 | self.pat_ident_binding_mode(span, val, hir::BindingAnnotation::Unannotated); | |
139 | let local_hir_id = self.lower_node_id(local.id); | |
140 | self.lower_attrs(local_hir_id, &local.attrs); | |
141 | // first statement which basically exists for the type annotation | |
142 | let stmt = { | |
143 | let local = self.arena.alloc(hir::Local { | |
144 | hir_id: local_hir_id, | |
145 | ty, | |
146 | pat, | |
147 | init, | |
148 | span, | |
149 | source: hir::LocalSource::Normal, | |
150 | }); | |
151 | let kind = hir::StmtKind::Local(local); | |
152 | hir::Stmt { hir_id: stmt_hir_id, kind, span } | |
153 | }; | |
154 | let let_expr = { | |
155 | let scrutinee = self.expr_ident(span, val, val_id); | |
156 | let let_kind = hir::ExprKind::Let(self.lower_pat(&local.pat), scrutinee, span); | |
157 | self.arena.alloc(self.expr(span, let_kind, AttrVec::new())) | |
158 | }; | |
159 | let then_expr = { | |
160 | let (stmts, expr) = self.lower_stmts(tail); | |
161 | let block = self.block_all(span, stmts, expr); | |
162 | self.arena.alloc(self.expr_block(block, AttrVec::new())) | |
163 | }; | |
164 | let else_expr = { | |
165 | let block = self.lower_block(els, false); | |
166 | self.arena.alloc(self.expr_block(block, AttrVec::new())) | |
167 | }; | |
168 | self.alias_attrs(else_expr.hir_id, local_hir_id); | |
169 | let if_expr = self.arena.alloc(hir::Expr { | |
170 | hir_id: self.next_id(), | |
171 | span, | |
172 | kind: hir::ExprKind::If(let_expr, then_expr, Some(else_expr)), | |
173 | }); | |
174 | if !self.sess.features_untracked().let_else { | |
175 | feature_err( | |
176 | &self.sess.parse_sess, | |
177 | sym::let_else, | |
178 | local.span, | |
179 | "`let...else` statements are unstable", | |
180 | ) | |
181 | .emit(); | |
182 | } | |
183 | (stmt, if_expr) | |
184 | } | |
185 | } |