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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195

use crate::{pass::Pass, util::undefined};
use ast::*;
use swc_common::{Fold, FoldWith, Spanned};

pub fn block_scoping() -> impl Pass {
    BlockScoping {
        in_loop_body: false,
    }
}

struct BlockScoping {
    in_loop_body: bool,
}

impl Fold<DoWhileStmt> for BlockScoping {
    fn fold(&mut self, node: DoWhileStmt) -> DoWhileStmt {
        let body = node
            .body
            .fold_with(&mut BlockScoping { in_loop_body: true });

        let test = node.test.fold_with(self);

        DoWhileStmt { body, test, ..node }
    }
}

impl Fold<WhileStmt> for BlockScoping {
    fn fold(&mut self, node: WhileStmt) -> WhileStmt {
        let body = node
            .body
            .fold_with(&mut BlockScoping { in_loop_body: true });

        let test = node.test.fold_with(&mut BlockScoping {
            in_loop_body: false,
        });

        WhileStmt { body, test, ..node }
    }
}

impl Fold<ForStmt> for BlockScoping {
    fn fold(&mut self, node: ForStmt) -> ForStmt {
        let body = node
            .body
            .fold_with(&mut BlockScoping { in_loop_body: true });

        let init = node.init.fold_with(&mut BlockScoping {
            in_loop_body: false,
        });
        let test = node.test.fold_with(&mut BlockScoping {
            in_loop_body: false,
        });
        let update = node.update.fold_with(&mut BlockScoping {
            in_loop_body: false,
        });

        ForStmt {
            init,
            test,
            update,
            body,
            ..node
        }
    }
}

impl Fold<ForOfStmt> for BlockScoping {
    fn fold(&mut self, node: ForOfStmt) -> ForOfStmt {
        let body = node
            .body
            .fold_with(&mut BlockScoping { in_loop_body: true });

        let left = node.left.fold_with(&mut BlockScoping {
            in_loop_body: false,
        });
        let right = node.right.fold_with(&mut BlockScoping {
            in_loop_body: false,
        });

        ForOfStmt {
            left,
            right,
            body,
            ..node
        }
    }
}

impl Fold<ForInStmt> for BlockScoping {
    fn fold(&mut self, node: ForInStmt) -> ForInStmt {
        let body = node
            .body
            .fold_with(&mut BlockScoping { in_loop_body: true });

        let left = node.left.fold_with(&mut BlockScoping {
            in_loop_body: false,
        });
        let right = node.right.fold_with(&mut BlockScoping {
            in_loop_body: false,
        });

        ForInStmt {
            left,
            right,
            body,
            ..node
        }
    }
}

impl Fold<Function> for BlockScoping {
    fn fold(&mut self, f: Function) -> Function {
        let f = f.fold_children(&mut BlockScoping {
            in_loop_body: false,
        });

        f
    }
}

impl Fold<ArrowExpr> for BlockScoping {
    fn fold(&mut self, f: ArrowExpr) -> ArrowExpr {
        let f = f.fold_children(&mut BlockScoping {
            in_loop_body: false,
        });

        f
    }
}

impl Fold<VarDecl> for BlockScoping {
    fn fold(&mut self, var: VarDecl) -> VarDecl {
        let var = var.fold_children(self);

        VarDecl {
            kind: VarDeclKind::Var,
            ..var
        }
    }
}

impl Fold<VarDeclarator> for BlockScoping {
    fn fold(&mut self, var: VarDeclarator) -> VarDeclarator {
        let var = var.fold_children(self);

        let init = if self.in_loop_body && var.init.is_none() {
            Some(undefined(var.span()))
        } else {
            var.init
        };

        VarDeclarator { init, ..var }
    }
}

#[cfg(test)]
mod tests {
    use super::block_scoping;

    test!(
        ::swc_ecma_parser::Syntax::default(),
        |_| block_scoping(),
        for_loop,
        "for (const key in obj) {
            const bar = obj[key];

            let qux;
            let fog;

            if (Array.isArray(bar)) {
            qux = bar[0];
            fog = bar[1];
            } else {
            qux = bar;
            }

            baz(key, qux, fog);
        }",
        "for (var key in obj) {
            var bar = obj[key];

            var qux = void 0;
            var fog = void 0;

            if (Array.isArray(bar)) {
            qux = bar[0];
            fog = bar[1];
            } else {
            qux = bar;
            }

            baz(key, qux, fog);
        }"
    );
}