On ModuleDecl

[Kyuuhachi]

I'm confused/annoyed at the design of ModuleDecl, which seems to be largely imported from estree. Ignoring things like spans and TypeScript, it basically boils down to:

enum ModuleDecl {
	Import {
		specifiers: Vec<enum {
			Named { local: Ident, imported: Option<IdentOrStr> },
			Default { local: Ident },
			Namespace { local: Ident },
		}>,
		src: Str,
	},
	ExportDecl {
		decl: Decl,
	},
	ExportNamed {
		specifiers: Vec<enum {
			Namespace { name: IdentOrStr },
			Default { exported: Ident },
			Named { orig: IdentOrStr, exported: Option<IdentOrStr> },
		}>,
		src: Option<Str>,
	},
	ExportDefaultDecl {
		decl: enum {
			Class(ClassExpr),
			Fn(FnExpr),
			TsInterfaceDecl(TsInterfaceDecl),
		},
	},
	ExportDefaultExpr {
		expr: Expr,
	},
	ExportAll {
		src: Str,
	}
}

There are several points I'm confused about:

• Why are exports and reexports (export {}; and export {} from "...";) joined? They have different both syntax and semantics. I imagine it makes parsing easier, though. If anything, import {} from "..."; and export {} from "..."; are are quite similar.
• Why are ExportDefaultDecl and ExportDefaultExpr split? I don't understand why export default function () {}; wouldn't be a ExportDefaultExpr. Only complicating factor seems to be TsInterfaceDecl, which I am not knowledgeable enough to speak about.
• Most importantly, why the Vec<Specifier> scheme, rather than just fixed fields? It makes any processing require awkward loops.

While I acknowledge that I may be oversimplifying certain parts, in my mind, the the ideal design would be something closer to

enum ModuleDecl {
	Import {
		default: Option<Ident>,
		namespace: Option<enum {
			All { local: Ident },
			Named {
				items: Vec<struct {
					imported: Option<IdentOrStr>,
					local: Ident,
				}>,
			},
		}>,
		src: Str,
	},

	ExportNamed {
		namespace: Vec<struct {
			local: Ident,
			exported: Option<IdentOrStr>,
		}>,
	},
	ExportDecl {
		decl: Decl,
	},
	ExportDefault {
		expr: Expr,
	},

	ReexportNamed {
		namespace: enum {
			All { local: Ident },
			Named {
				items: Vec<struct {
					imported: Option<IdentOrStr>,
					exported: IdentOrStr,
				}>,
			},
		},
		src: Str,
	},
	ReexportAll {
		src: Str,
	},
}

I believe this structure more closely reflects the actual set of allowed productions, making it less error-prone; and removing the Vec<Specifier> scheme makes it significantly easier to work with. The obvious downside is that it's a majorly breaking change.

Should you judge this to be a worthwhile change, I would be willing to attempt to implement it.

[kdy1]

1. It's AST. Those two are syntactically very similar.
2. Export Default Decl and Export Default Expr has different hoistng semantics.
3. It's based on estree, and your AST looks more complex than the current one.