refactor(vm): Allow nested binding patterns to be simple #401
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aapoalas
previously approved these changes
Aug 25, 2024
Array and object binding patterns can be either simple or complex, where simple patterns are compiled in a way that jumps into a separate execution context where only binding-related bytecode instructions are supported. Currently, if an array or object binding pattern contains another binding pattern, that automatically makes the outer pattern complex. However, that doesn't need to be the case, as long as none of the nested patterns, no matter how deeply nested, have initializers or computed property keys. As it turns out, the spec has a syntax-directed operation called `ContainsExpression` that checks exactly this, and which affects the behavior of `FunctionDeclarationInstantiation`. Our implementation currently does not use that, since we don't yet support bindings or initializers in function parameters, which is why we don't yet implement it. This patch adds an implementation for that, and uses it to enable nested simple binding patterns.
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aapoalas
previously approved these changes
Aug 25, 2024
aapoalas
approved these changes
Aug 25, 2024
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Array and object binding patterns can be either simple or complex, where simple patterns are compiled in a way that jumps into a separate execution context where only binding-related bytecode instructions are supported.
Currently, if an array or object binding pattern contains another binding pattern, that automatically makes the outer pattern complex. However, that doesn't need to be the case, as long as none of the nested patterns, no matter how deeply nested, have initializers or computed property keys.
As it turns out, the spec has a syntax-directed operation called
ContainsExpressionthat checks exactly this, and which affects the behavior ofFunctionDeclarationInstantiation. Our implementation currently does not use that, since we don't yet support bindings or initializers in function parameters, which is why we don't yet implement it. This patch adds an implementation for that, and uses it to enable nested simple binding patterns.This PR builds on top of #398, #399 and #400, do not merge before those.