Roadmap

[kdy1]

AST Stabilization plan

• Collect opinions about AST. Ideas for AST changes #9161
• Add #[non_exhaustive] to relevant nodes

[magic-akari]

• Provide AST count information without a separate visitor pass #9401

A lot of information can be obtained during the lexer/parser phase.
For example,

1. We can do things like cjs-module-lexer
2. We can also create an es-check tool to detect whether there is any uncompiled code in the final product code.
3. Skip some transformation passes

There are also other very useful pieces of information, such as the features described here, which we can get right after parsing is finished:

swc/crates/swc_ecma_preset_env/src/transform_data.rs

Lines 25 to 199 in f4cab32

	pub enum Feature {
	/// `transform-template-literals`
	TemplateLiterals,
	/// `transform-literals`
	Literals,
	/// `transform-function-name`
	FunctionName,
	/// `transform-arrow-functions`
	ArrowFunctions,
	/// `transform-block-scoped-functions`
	BlockScopedFunctions,
	/// `transform-classes`
	Classes,
	/// `transform-object-super`
	ObjectSuper,
	/// `transform-shorthand-properties`
	ShorthandProperties,
	/// `transform-duplicate-keys`
	DuplicateKeys,
	/// `transform-computed-properties`
	ComputedProperties,
	/// `transform-for-of`
	ForOf,
	/// `transform-sticky-regex`
	StickyRegex,
	/// `transform-dotall-regex`
	DotAllRegex,
	/// `transform-unicode-regex`
	UnicodeRegex,
	/// `transform-spread`
	Spread,
	/// `transform-parameters`
	Parameters,
	/// `transform-destructuring`
	Destructuring,
	/// `transform-block-scoping`
	BlockScoping,
	/// `transform-typeof-symbol`
	TypeOfSymbol,
	/// `transform-new-target`
	NewTarget,
	/// `transform-regenerator`
	Regenerator,
	/// `transform-exponentiation-operator`
	ExponentiationOperator,
	/// `transform-async-to-generator`
	AsyncToGenerator,
	/// `transform-async-generator-functions`
	#[string_enum(alias("proposal-async-generator-functions"))]
	AsyncGeneratorFunctions,
	/// `transform-object-rest-spread`
	#[string_enum(alias("proposal-object-rest-spread"))]
	ObjectRestSpread,
	/// `transform-unicode-property-regex`
	#[string_enum(alias("proposal-unicode-property-regex"))]
	UnicodePropertyRegex,
	/// `transform-json-strings`
	#[string_enum(alias("proposal-json-strings"))]
	JsonStrings,
	/// `transform-optional-catch-binding`
	#[string_enum(alias("proposal-optional-catch-binding"))]
	OptionalCatchBinding,
	/// `transform-named-capturing-groups-regex`
	NamedCapturingGroupsRegex,
	/// `transform-member-expression-literals`
	MemberExpressionLiterals,
	/// `transform-property-literals`
	PropertyLiterals,
	/// `transform-reserved-words`
	ReservedWords,
	/// `transform-export-namespace-from`
	#[string_enum(alias("proposal-export-namespace-from"))]
	ExportNamespaceFrom,
	/// `transform-nullish-coalescing-operator`
	#[string_enum(alias("proposal-nullish-coalescing-operator"))]
	NullishCoalescing,
	/// `transform-logical-assignment-operators`
	#[string_enum(alias("proposal-logical-assignment-operators"))]
	LogicalAssignmentOperators,
	/// `transform-optional-chaining`
	#[string_enum(alias("proposal-optional-chaining"))]
	OptionalChaining,
	/// `transform-class-properties`
	#[string_enum(alias("proposal-class-properties"))]
	ClassProperties,
	/// `transform-numeric-separator`
	#[string_enum(alias("proposal-numeric-separator"))]
	NumericSeparator,
	/// `transform-private-methods`
	#[string_enum(alias("proposal-private-methods"))]
	PrivateMethods,
	/// `transform-class-static-block`
	#[string_enum(alias("proposal-class-static-block"))]
	ClassStaticBlock,
	/// `transform-private-property-in-object`
	#[string_enum(alias("proposal-private-property-in-object"))]
	PrivatePropertyInObject,
	/// `transform-unicode-escapes`
	UnicodeEscapes,
	/// `transform-unicode-sets-regex`
	UnicodeSetsRegex,
	/// `bugfix/transform-async-arrows-in-class`
	BugfixAsyncArrowsInClass,
	/// `bugfix/transform-edge-default-parameters`
	BugfixEdgeDefaultParam,
	/// `bugfix/transform-tagged-template-caching`
	BugfixTaggedTemplateCaching,
	/// `bugfix/transform-safari-id-destructuring-collision-in-function-expression`
	BugfixSafariIdDestructuringCollisionInFunctionExpression,
	/// `bugfix/transform-edge-function-name`
	BugfixTransformEdgeFunctionName, // TODO
	/// `bugfix/transform-safari-block-shadowing`
	BugfixTransformSafariBlockShadowing, // TODO
	/// `bugfix/transform-safari-for-shadowing`
	BugfixTransformSafariForShadowing, // TODO
	/// `bugfix/transform-v8-spread-parameters-in-optional-chaining`
	BugfixTransformV8SpreadParametersInOptionalChaining, // TODO
	/// `bugfix/transform-v8-static-class-fields-redefine-readonly`
	BugfixTransformV8StaticClassFieldsRedefineReadonly, // TODO
	/// `bugfix/transform-firefox-class-in-computed-class-key`
	BugfixTransformFirefoxClassInComputedClassKey, // TODO
	}

If we know in advance that there are no classes in the code, then all passes related to classes can be skipped.

[kdy1]

@magic-akari It sounds very interesting. I'll work on it after finishing the tasks in my hand.