1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

use crate::thir::cx::Cx;

use rustc_hir as hir;
use rustc_middle::middle::region;
use rustc_middle::thir::*;
use rustc_middle::ty;

use rustc_index::Idx;
use rustc_middle::ty::CanonicalUserTypeAnnotation;

impl<'tcx> Cx<'tcx> {
    pub(crate) fn mirror_block(&mut self, block: &'tcx hir::Block<'tcx>) -> BlockId {
        // We have to eagerly lower the "spine" of the statements
        // in order to get the lexical scoping correctly.
        let stmts = self.mirror_stmts(block.hir_id.local_id, block.stmts);
        let opt_destruction_scope =
            self.region_scope_tree.opt_destruction_scope(block.hir_id.local_id);
        let block = Block {
            targeted_by_break: block.targeted_by_break,
            region_scope: region::Scope {
                id: block.hir_id.local_id,
                data: region::ScopeData::Node,
            },
            opt_destruction_scope,
            span: block.span,
            stmts,
            expr: block.expr.map(|expr| self.mirror_expr(expr)),
            safety_mode: match block.rules {
                hir::BlockCheckMode::DefaultBlock => BlockSafety::Safe,
                hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::CompilerGenerated) => {
                    BlockSafety::BuiltinUnsafe
                }
                hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::UserProvided) => {
                    BlockSafety::ExplicitUnsafe(block.hir_id)
                }
            },
        };

        self.thir.blocks.push(block)
    }

    fn mirror_stmts(
        &mut self,
        block_id: hir::ItemLocalId,
        stmts: &'tcx [hir::Stmt<'tcx>],
    ) -> Box<[StmtId]> {
        stmts
            .iter()
            .enumerate()
            .filter_map(|(index, stmt)| {
                let hir_id = stmt.hir_id;
                let opt_dxn_ext = self.region_scope_tree.opt_destruction_scope(hir_id.local_id);
                match stmt.kind {
                    hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
                        let stmt = Stmt {
                            kind: StmtKind::Expr {
                                scope: region::Scope {
                                    id: hir_id.local_id,
                                    data: region::ScopeData::Node,
                                },
                                expr: self.mirror_expr(expr),
                            },
                            opt_destruction_scope: opt_dxn_ext,
                        };
                        Some(self.thir.stmts.push(stmt))
                    }
                    hir::StmtKind::Item(..) => {
                        // ignore for purposes of the MIR
                        None
                    }
                    hir::StmtKind::Local(ref local) => {
                        let remainder_scope = region::Scope {
                            id: block_id,
                            data: region::ScopeData::Remainder(region::FirstStatementIndex::new(
                                index,
                            )),
                        };

                        let else_block = local.els.map(|els| self.mirror_block(els));

                        let mut pattern = self.pattern_from_hir(local.pat);
                        debug!(?pattern);

                        if let Some(ty) = &local.ty {
                            if let Some(&user_ty) =
                                self.typeck_results.user_provided_types().get(ty.hir_id)
                            {
                                debug!("mirror_stmts: user_ty={:?}", user_ty);
                                let annotation = CanonicalUserTypeAnnotation {
                                    user_ty: Box::new(user_ty),
                                    span: ty.span,
                                    inferred_ty: self.typeck_results.node_type(ty.hir_id),
                                };
                                pattern = Box::new(Pat {
                                    ty: pattern.ty,
                                    span: pattern.span,
                                    kind: PatKind::AscribeUserType {
                                        ascription: Ascription {
                                            annotation,
                                            variance: ty::Variance::Covariant,
                                        },
                                        subpattern: pattern,
                                    },
                                });
                            }
                        }

                        let span = match local.init {
                            Some(init) => local.span.with_hi(init.span.hi()),
                            None => local.span,
                        };
                        let stmt = Stmt {
                            kind: StmtKind::Let {
                                remainder_scope,
                                init_scope: region::Scope {
                                    id: hir_id.local_id,
                                    data: region::ScopeData::Node,
                                },
                                pattern,
                                initializer: local.init.map(|init| self.mirror_expr(init)),
                                else_block,
                                lint_level: LintLevel::Explicit(local.hir_id),
                                span,
                            },
                            opt_destruction_scope: opt_dxn_ext,
                        };
                        Some(self.thir.stmts.push(stmt))
                    }
                }
            })
            .collect()
    }
}