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Max Brunsfeld
25b8facc6c
These tests are easier to write and maintain if the grammars are just JS, like grammars normally are. It doesn't slow the tests down significantly to shell out to `node` for each of these grammars.
38 lines
1.2 KiB
JavaScript
38 lines
1.2 KiB
JavaScript
// Normally, when there are invisible rules (rules whose names start with an `_`) that simply wrap
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// another rule, there is an optimization at parser-generation time called *Unit Reduction
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// Elimination* that avoids creating nodes for those rules at runtime. One case where this
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// optimization must *not* be applied is when those invisible rules are going to be aliased within
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// their parent rule. In that situation, eliminating the invisible node could cause the alias to be
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// incorrectly applied to its child.
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module.exports = grammar({
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name: 'aliased_unit_reductions',
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extras: $ => [/\s/],
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rules: {
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statement: $ => seq(
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$._a,
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// The `_b` rule is always aliased to `b_prime`, so it is internally treated
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// as a simple alias.
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alias($._b, $.b_prime),
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// The `_c` rule is used without an alias in addition to being aliased to `c_prime`,
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// so it is not a simple alias.
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alias($._c, $.c_prime),
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$._c,
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';'
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),
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_a: $ => $._A,
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_b: $ => $._B,
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_c: $ => $._C,
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_A: $ => $.identifier,
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_B: $ => $.identifier,
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_C: $ => $.identifier,
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identifier: $ => /[a-z]+/,
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}
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}); |