14.1.12 Static Semantics: IsFunctionDefinition #536
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I agree. (This also applies to classes and generator functions.) |
jmdyck
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In practice, an `<emu-mods>` contains an `<emu-params>` and/or an `<emu-opt>`. My guess is that this rule was introduced with only `<emu-params>` in mind, as there are situations in which you might reasonably want to suppress the display of `<emu-params>`, but you should never suppress an `<emu-opt>`. --- An alternative to removing the rule (and, if my above guess is correct, a solution that would be more in line with the original intent) would be to change its selector from: `emu-production[collapsed] emu-mods` to: `emu-production[collapsed] emu-params` I.e., in a collapsed production, suppress the display of *only* the grammatical parameters (GPs). However, I didn't propose that solution because it's incomplete in 3 ways: - It doesn't suppress GPs in all contexts where we want to suppress them. (Generally we want to suppress GPs in any non-defining production, which includes all the collapsed production, but also includes lots of non-collapsed productions.) - It doesn't suppress all the annotations we typically want to suppress (e.g. lookahead restrictions and no-LineTerminator-here annotations) because those don't occur in `<emu-mods>`. - It doesn't allow for the rare cases where we *don't* want to suppress GPs (and annotations). Instead (in ecma262 at least), we explicitly remove unnecessary GPs and annotations from all productions where we don't want them to appear. (Note that this also has the benefit of making the source easier to read.) So even with the suggested modification, the rule would be basically pointless. Better to just delete it. --- This resolves issue tc39#108, and also: - tc39/ecma262#536 - tc39/ecma262#908 - tc39/ecma262#1139 - tc39/ecma262#1663
ljharb
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Jan 17, 2020
In practice, an `<emu-mods>` contains an `<emu-params>` and/or an `<emu-opt>`. My guess is that this rule was introduced with only `<emu-params>` in mind, as there are situations in which you might reasonably want to suppress the display of `<emu-params>`, but you should never suppress an `<emu-opt>`. --- An alternative to removing the rule (and, if my above guess is correct, a solution that would be more in line with the original intent) would be to change its selector from: `emu-production[collapsed] emu-mods` to: `emu-production[collapsed] emu-params` I.e., in a collapsed production, suppress the display of *only* the grammatical parameters (GPs). However, I didn't propose that solution because it's incomplete in 3 ways: - It doesn't suppress GPs in all contexts where we want to suppress them. (Generally we want to suppress GPs in any non-defining production, which includes all the collapsed production, but also includes lots of non-collapsed productions.) - It doesn't suppress all the annotations we typically want to suppress (e.g. lookahead restrictions and no-LineTerminator-here annotations) because those don't occur in `<emu-mods>`. - It doesn't allow for the rare cases where we *don't* want to suppress GPs (and annotations). Instead (in ecma262 at least), we explicitly remove unnecessary GPs and annotations from all productions where we don't want them to appear. (Note that this also has the benefit of making the source easier to read.) So even with the suggested modification, the rule would be basically pointless. Better to just delete it. --- This resolves issue tc39#108, and also: - tc39/ecma262#536 - tc39/ecma262#908 - tc39/ecma262#1139 - tc39/ecma262#1663
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I think there is something missing in IsFunctionDefinition at 14.1.12. The operation as described here will only return true if the given production is a named function definition, but false for anonymous function definitions.
Therefore when calling IsAnonymousFunctionDefinition with argument production, the first algorithm step would always return false for anonymous function expressions and the operation HasName would be unreachable.
So it rather should be:
14.1.12 Static Semantics: IsFunctionDefinition
FunctionExpression: function (FormalParameters) {FunctionBody}
FunctionExpression: function BindingIdentifier (FormalParameters) {FunctionBody}
Return true.
[as in ES2015: IsFunctionDefiniton]
Or is there a reason for changing this?
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