AST template macros

This is the code we have to write in transformer to generate let Foo;:

let kind = VariableDeclarationKind::Let;
let declarations = {
    let ident = BindingIdentifier::new(SPAN, name.clone());
    let pattern_kind = self.ctx.ast.binding_pattern_identifier(ident);
    let binding = self.ctx.ast.binding_pattern(pattern_kind, None, false);
    let decl = self.ctx.ast.variable_declarator(SPAN, kind, binding, None, false);
    self.ctx.ast.new_vec_single(decl)
};
Declaration::VariableDeclaration(self.ctx.ast.variable_declaration(
    SPAN,
    kind,
    declarations,
    Modifiers::empty(),
))

Seems a bit bananas! Very long to write, and non-trivial to understand at first glance what the code is doing.

Surely we can find some way to reduce this.

Like: ast!{ let #name; }

The obvious problem is compile time impact of macros. Can we find some way to precompile macro expansion so we can enjoy a simpler code style without paying the compile-time price?

Start in the transformer code that manually constructs the let Foo; AST and trace the AST builder calls shown in the issue. Investigate whether an ast!{ let #name; }-style macro or precompiled expansion can reduce this code without unacceptable compile-time impact. Done means a concrete, validated approach for simpler AST generation with its compile-time trade-offs understood.