use crate::base::ExtCtxt;

use rustc_ast::attr;
use rustc_ast::ptr::P;
use rustc_ast::{self as ast, AttrVec, BlockCheckMode, Expr, PatKind, UnOp};
use rustc_span::source_map::Spanned;
use rustc_span::symbol::{kw, sym, Ident, Symbol};

use rustc_span::Span;

impl<'a> ExtCtxt<'a> {
    pub fn path(&self, span: Span, strs: Vec<Ident>) -> ast::Path {
        self.path_all(span, false, strs, vec![])
    }
    pub fn path_ident(&self, span: Span, id: Ident) -> ast::Path {
        self.path(span, vec![id])
    }
    pub fn path_global(&self, span: Span, strs: Vec<Ident>) -> ast::Path {
        self.path_all(span, true, strs, vec![])
    }
    pub fn path_all(
        &self,
        span: Span,
        global: bool,
        mut idents: Vec<Ident>,
        args: Vec<ast::GenericArg>,
    ) -> ast::Path {
        assert!(!idents.is_empty());
        let add_root = global && !idents[0].is_path_segment_keyword();
        let mut segments = Vec::with_capacity(idents.len() + add_root as usize);
        if add_root {
            segments.push(ast::PathSegment::path_root(span));
        }
        let last_ident = idents.pop().unwrap();
        segments.extend(
            idents.into_iter().map(|ident| ast::PathSegment::from_ident(ident.with_span_pos(span))),
        );
        let args = if !args.is_empty() {
            let args = args.into_iter().map(ast::AngleBracketedArg::Arg).collect();
            ast::AngleBracketedArgs { args, span }.into()
        } else {
            None
        };
        segments.push(ast::PathSegment {
            ident: last_ident.with_span_pos(span),
            id: ast::DUMMY_NODE_ID,
            args,
        });
        ast::Path { span, segments, tokens: None }
    }

    pub fn ty_mt(&self, ty: P<ast::Ty>, mutbl: ast::Mutability) -> ast::MutTy {
        ast::MutTy { ty, mutbl }
    }

    pub fn ty(&self, span: Span, kind: ast::TyKind) -> P<ast::Ty> {
        P(ast::Ty { id: ast::DUMMY_NODE_ID, span, kind, tokens: None })
    }

    pub fn ty_path(&self, path: ast::Path) -> P<ast::Ty> {
        self.ty(path.span, ast::TyKind::Path(None, path))
    }

    // Might need to take bounds as an argument in the future, if you ever want
    // to generate a bounded existential trait type.
    pub fn ty_ident(&self, span: Span, ident: Ident) -> P<ast::Ty> {
        self.ty_path(self.path_ident(span, ident))
    }

    pub fn anon_const(&self, span: Span, kind: ast::ExprKind) -> ast::AnonConst {
        ast::AnonConst {
            id: ast::DUMMY_NODE_ID,
            value: P(ast::Expr {
                id: ast::DUMMY_NODE_ID,
                kind,
                span,
                attrs: AttrVec::new(),
                tokens: None,
            }),
        }
    }

    pub fn const_ident(&self, span: Span, ident: Ident) -> ast::AnonConst {
        self.anon_const(span, ast::ExprKind::Path(None, self.path_ident(span, ident)))
    }

    pub fn ty_rptr(
        &self,
        span: Span,
        ty: P<ast::Ty>,
        lifetime: Option<ast::Lifetime>,
        mutbl: ast::Mutability,
    ) -> P<ast::Ty> {
        self.ty(span, ast::TyKind::Rptr(lifetime, self.ty_mt(ty, mutbl)))
    }

    pub fn ty_ptr(&self, span: Span, ty: P<ast::Ty>, mutbl: ast::Mutability) -> P<ast::Ty> {
        self.ty(span, ast::TyKind::Ptr(self.ty_mt(ty, mutbl)))
    }

    pub fn typaram(
        &self,
        span: Span,
        ident: Ident,
        attrs: Vec<ast::Attribute>,
        bounds: ast::GenericBounds,
        default: Option<P<ast::Ty>>,
    ) -> ast::GenericParam {
        ast::GenericParam {
            ident: ident.with_span_pos(span),
            id: ast::DUMMY_NODE_ID,
            attrs: attrs.into(),
            bounds,
            kind: ast::GenericParamKind::Type { default },
            is_placeholder: false,
        }
    }

    pub fn trait_ref(&self, path: ast::Path) -> ast::TraitRef {
        ast::TraitRef { path, ref_id: ast::DUMMY_NODE_ID }
    }

    pub fn poly_trait_ref(&self, span: Span, path: ast::Path) -> ast::PolyTraitRef {
        ast::PolyTraitRef {
            bound_generic_params: Vec::new(),
            trait_ref: self.trait_ref(path),
            span,
        }
    }

    pub fn trait_bound(&self, path: ast::Path) -> ast::GenericBound {
        ast::GenericBound::Trait(
            self.poly_trait_ref(path.span, path),
            ast::TraitBoundModifier::None,
        )
    }

    pub fn lifetime(&self, span: Span, ident: Ident) -> ast::Lifetime {
        ast::Lifetime { id: ast::DUMMY_NODE_ID, ident: ident.with_span_pos(span) }
    }

    pub fn lifetime_def(
        &self,
        span: Span,
        ident: Ident,
        attrs: Vec<ast::Attribute>,
        bounds: ast::GenericBounds,
    ) -> ast::GenericParam {
        let lifetime = self.lifetime(span, ident);
        ast::GenericParam {
            ident: lifetime.ident,
            id: lifetime.id,
            attrs: attrs.into(),
            bounds,
            kind: ast::GenericParamKind::Lifetime,
            is_placeholder: false,
        }
    }

    pub fn stmt_expr(&self, expr: P<ast::Expr>) -> ast::Stmt {
        ast::Stmt {
            id: ast::DUMMY_NODE_ID,
            span: expr.span,
            kind: ast::StmtKind::Expr(expr),
            tokens: None,
        }
    }

    pub fn stmt_let(&self, sp: Span, mutbl: bool, ident: Ident, ex: P<ast::Expr>) -> ast::Stmt {
        let pat = if mutbl {
            let binding_mode = ast::BindingMode::ByValue(ast::Mutability::Mut);
            self.pat_ident_binding_mode(sp, ident, binding_mode)
        } else {
            self.pat_ident(sp, ident)
        };
        let local = P(ast::Local {
            pat,
            ty: None,
            init: Some(ex),
            id: ast::DUMMY_NODE_ID,
            span: sp,
            attrs: AttrVec::new(),
        });
        ast::Stmt {
            id: ast::DUMMY_NODE_ID,
            kind: ast::StmtKind::Local(local),
            span: sp,
            tokens: None,
        }
    }

    // Generates `let _: Type;`, which is usually used for type assertions.
    pub fn stmt_let_type_only(&self, span: Span, ty: P<ast::Ty>) -> ast::Stmt {
        let local = P(ast::Local {
            pat: self.pat_wild(span),
            ty: Some(ty),
            init: None,
            id: ast::DUMMY_NODE_ID,
            span,
            attrs: AttrVec::new(),
        });
        ast::Stmt { id: ast::DUMMY_NODE_ID, kind: ast::StmtKind::Local(local), span, tokens: None }
    }

    pub fn stmt_item(&self, sp: Span, item: P<ast::Item>) -> ast::Stmt {
        ast::Stmt {
            id: ast::DUMMY_NODE_ID,
            kind: ast::StmtKind::Item(item),
            span: sp,
            tokens: None,
        }
    }

    pub fn block_expr(&self, expr: P<ast::Expr>) -> P<ast::Block> {
        self.block(
            expr.span,
            vec![ast::Stmt {
                id: ast::DUMMY_NODE_ID,
                span: expr.span,
                kind: ast::StmtKind::Expr(expr),
                tokens: None,
            }],
        )
    }
    pub fn block(&self, span: Span, stmts: Vec<ast::Stmt>) -> P<ast::Block> {
        P(ast::Block {
            stmts,
            id: ast::DUMMY_NODE_ID,
            rules: BlockCheckMode::Default,
            span,
            tokens: None,
        })
    }

    pub fn expr(&self, span: Span, kind: ast::ExprKind) -> P<ast::Expr> {
        P(ast::Expr { id: ast::DUMMY_NODE_ID, kind, span, attrs: AttrVec::new(), tokens: None })
    }

    pub fn expr_path(&self, path: ast::Path) -> P<ast::Expr> {
        self.expr(path.span, ast::ExprKind::Path(None, path))
    }

    pub fn expr_ident(&self, span: Span, id: Ident) -> P<ast::Expr> {
        self.expr_path(self.path_ident(span, id))
    }
    pub fn expr_self(&self, span: Span) -> P<ast::Expr> {
        self.expr_ident(span, Ident::with_dummy_span(kw::SelfLower))
    }

    pub fn expr_binary(
        &self,
        sp: Span,
        op: ast::BinOpKind,
        lhs: P<ast::Expr>,
        rhs: P<ast::Expr>,
    ) -> P<ast::Expr> {
        self.expr(sp, ast::ExprKind::Binary(Spanned { node: op, span: sp }, lhs, rhs))
    }

    pub fn expr_deref(&self, sp: Span, e: P<ast::Expr>) -> P<ast::Expr> {
        self.expr(sp, ast::ExprKind::Unary(UnOp::Deref, e))
    }

    pub fn expr_addr_of(&self, sp: Span, e: P<ast::Expr>) -> P<ast::Expr> {
        self.expr(sp, ast::ExprKind::AddrOf(ast::BorrowKind::Ref, ast::Mutability::Not, e))
    }

    pub fn expr_call(
        &self,
        span: Span,
        expr: P<ast::Expr>,
        args: Vec<P<ast::Expr>>,
    ) -> P<ast::Expr> {
        self.expr(span, ast::ExprKind::Call(expr, args))
    }
    pub fn expr_call_ident(&self, span: Span, id: Ident, args: Vec<P<ast::Expr>>) -> P<ast::Expr> {
        self.expr(span, ast::ExprKind::Call(self.expr_ident(span, id), args))
    }
    pub fn expr_call_global(
        &self,
        sp: Span,
        fn_path: Vec<Ident>,
        args: Vec<P<ast::Expr>>,
    ) -> P<ast::Expr> {
        let pathexpr = self.expr_path(self.path_global(sp, fn_path));
        self.expr_call(sp, pathexpr, args)
    }
    pub fn expr_method_call(
        &self,
        span: Span,
        expr: P<ast::Expr>,
        ident: Ident,
        mut args: Vec<P<ast::Expr>>,
    ) -> P<ast::Expr> {
        args.insert(0, expr);
        let segment = ast::PathSegment::from_ident(ident.with_span_pos(span));
        self.expr(span, ast::ExprKind::MethodCall(segment, args, span))
    }
    pub fn expr_block(&self, b: P<ast::Block>) -> P<ast::Expr> {
        self.expr(b.span, ast::ExprKind::Block(b, None))
    }
    pub fn field_imm(&self, span: Span, ident: Ident, e: P<ast::Expr>) -> ast::Field {
        ast::Field {
            ident: ident.with_span_pos(span),
            expr: e,
            span,
            is_shorthand: false,
            attrs: AttrVec::new(),
            id: ast::DUMMY_NODE_ID,
            is_placeholder: false,
        }
    }
    pub fn expr_struct(
        &self,
        span: Span,
        path: ast::Path,
        fields: Vec<ast::Field>,
    ) -> P<ast::Expr> {
        self.expr(span, ast::ExprKind::Struct(path, fields, None))
    }
    pub fn expr_struct_ident(
        &self,
        span: Span,
        id: Ident,
        fields: Vec<ast::Field>,
    ) -> P<ast::Expr> {
        self.expr_struct(span, self.path_ident(span, id), fields)
    }

    pub fn expr_lit(&self, span: Span, lit_kind: ast::LitKind) -> P<ast::Expr> {
        let lit = ast::Lit::from_lit_kind(lit_kind, span);
        self.expr(span, ast::ExprKind::Lit(lit))
    }
    pub fn expr_usize(&self, span: Span, i: usize) -> P<ast::Expr> {
        self.expr_lit(
            span,
            ast::LitKind::Int(i as u128, ast::LitIntType::Unsigned(ast::UintTy::Usize)),
        )
    }
    pub fn expr_u32(&self, sp: Span, u: u32) -> P<ast::Expr> {
        self.expr_lit(sp, ast::LitKind::Int(u as u128, ast::LitIntType::Unsigned(ast::UintTy::U32)))
    }
    pub fn expr_bool(&self, sp: Span, value: bool) -> P<ast::Expr> {
        self.expr_lit(sp, ast::LitKind::Bool(value))
    }

    pub fn expr_vec(&self, sp: Span, exprs: Vec<P<ast::Expr>>) -> P<ast::Expr> {
        self.expr(sp, ast::ExprKind::Array(exprs))
    }
    pub fn expr_vec_slice(&self, sp: Span, exprs: Vec<P<ast::Expr>>) -> P<ast::Expr> {
        self.expr_addr_of(sp, self.expr_vec(sp, exprs))
    }
    pub fn expr_str(&self, sp: Span, s: Symbol) -> P<ast::Expr> {
        self.expr_lit(sp, ast::LitKind::Str(s, ast::StrStyle::Cooked))
    }

    pub fn expr_cast(&self, sp: Span, expr: P<ast::Expr>, ty: P<ast::Ty>) -> P<ast::Expr> {
        self.expr(sp, ast::ExprKind::Cast(expr, ty))
    }

    pub fn expr_some(&self, sp: Span, expr: P<ast::Expr>) -> P<ast::Expr> {
        let some = self.std_path(&[sym::option, sym::Option, sym::Some]);
        self.expr_call_global(sp, some, vec![expr])
    }

    pub fn expr_tuple(&self, sp: Span, exprs: Vec<P<ast::Expr>>) -> P<ast::Expr> {
        self.expr(sp, ast::ExprKind::Tup(exprs))
    }

    pub fn expr_fail(&self, span: Span, msg: Symbol) -> P<ast::Expr> {
        self.expr_call_global(
            span,
            [sym::std, sym::rt, sym::begin_panic].iter().map(|s| Ident::new(*s, span)).collect(),
            vec![self.expr_str(span, msg)],
        )
    }

    pub fn expr_unreachable(&self, span: Span) -> P<ast::Expr> {
        self.expr_fail(span, Symbol::intern("internal error: entered unreachable code"))
    }

    pub fn expr_ok(&self, sp: Span, expr: P<ast::Expr>) -> P<ast::Expr> {
        let ok = self.std_path(&[sym::result, sym::Result, sym::Ok]);
        self.expr_call_global(sp, ok, vec![expr])
    }

    pub fn expr_try(&self, sp: Span, head: P<ast::Expr>) -> P<ast::Expr> {
        let ok = self.std_path(&[sym::result, sym::Result, sym::Ok]);
        let ok_path = self.path_global(sp, ok);
        let err = self.std_path(&[sym::result, sym::Result, sym::Err]);
        let err_path = self.path_global(sp, err);

        let binding_variable = Ident::new(sym::__try_var, sp);
        let binding_pat = self.pat_ident(sp, binding_variable);
        let binding_expr = self.expr_ident(sp, binding_variable);

        // `Ok(__try_var)` pattern
        let ok_pat = self.pat_tuple_struct(sp, ok_path, vec![binding_pat.clone()]);

        // `Err(__try_var)` (pattern and expression respectively)
        let err_pat = self.pat_tuple_struct(sp, err_path.clone(), vec![binding_pat]);
        let err_inner_expr =
            self.expr_call(sp, self.expr_path(err_path), vec![binding_expr.clone()]);
        // `return Err(__try_var)`
        let err_expr = self.expr(sp, ast::ExprKind::Ret(Some(err_inner_expr)));

        // `Ok(__try_var) => __try_var`
        let ok_arm = self.arm(sp, ok_pat, binding_expr);
        // `Err(__try_var) => return Err(__try_var)`
        let err_arm = self.arm(sp, err_pat, err_expr);

        // `match head { Ok() => ..., Err() => ... }`
        self.expr_match(sp, head, vec![ok_arm, err_arm])
    }

    pub fn pat(&self, span: Span, kind: PatKind) -> P<ast::Pat> {
        P(ast::Pat { id: ast::DUMMY_NODE_ID, kind, span, tokens: None })
    }
    pub fn pat_wild(&self, span: Span) -> P<ast::Pat> {
        self.pat(span, PatKind::Wild)
    }
    pub fn pat_lit(&self, span: Span, expr: P<ast::Expr>) -> P<ast::Pat> {
        self.pat(span, PatKind::Lit(expr))
    }
    pub fn pat_ident(&self, span: Span, ident: Ident) -> P<ast::Pat> {
        let binding_mode = ast::BindingMode::ByValue(ast::Mutability::Not);
        self.pat_ident_binding_mode(span, ident, binding_mode)
    }

    pub fn pat_ident_binding_mode(
        &self,
        span: Span,
        ident: Ident,
        bm: ast::BindingMode,
    ) -> P<ast::Pat> {
        let pat = PatKind::Ident(bm, ident.with_span_pos(span), None);
        self.pat(span, pat)
    }
    pub fn pat_path(&self, span: Span, path: ast::Path) -> P<ast::Pat> {
        self.pat(span, PatKind::Path(None, path))
    }
    pub fn pat_tuple_struct(
        &self,
        span: Span,
        path: ast::Path,
        subpats: Vec<P<ast::Pat>>,
    ) -> P<ast::Pat> {
        self.pat(span, PatKind::TupleStruct(path, subpats))
    }
    pub fn pat_struct(
        &self,
        span: Span,
        path: ast::Path,
        field_pats: Vec<ast::FieldPat>,
    ) -> P<ast::Pat> {
        self.pat(span, PatKind::Struct(path, field_pats, false))
    }
    pub fn pat_tuple(&self, span: Span, pats: Vec<P<ast::Pat>>) -> P<ast::Pat> {
        self.pat(span, PatKind::Tuple(pats))
    }

    pub fn pat_some(&self, span: Span, pat: P<ast::Pat>) -> P<ast::Pat> {
        let some = self.std_path(&[sym::option, sym::Option, sym::Some]);
        let path = self.path_global(span, some);
        self.pat_tuple_struct(span, path, vec![pat])
    }

    pub fn pat_none(&self, span: Span) -> P<ast::Pat> {
        let some = self.std_path(&[sym::option, sym::Option, sym::None]);
        let path = self.path_global(span, some);
        self.pat_path(span, path)
    }

    pub fn pat_ok(&self, span: Span, pat: P<ast::Pat>) -> P<ast::Pat> {
        let some = self.std_path(&[sym::result, sym::Result, sym::Ok]);
        let path = self.path_global(span, some);
        self.pat_tuple_struct(span, path, vec![pat])
    }

    pub fn pat_err(&self, span: Span, pat: P<ast::Pat>) -> P<ast::Pat> {
        let some = self.std_path(&[sym::result, sym::Result, sym::Err]);
        let path = self.path_global(span, some);
        self.pat_tuple_struct(span, path, vec![pat])
    }

    pub fn arm(&self, span: Span, pat: P<ast::Pat>, expr: P<ast::Expr>) -> ast::Arm {
        ast::Arm {
            attrs: vec![],
            pat,
            guard: None,
            body: expr,
            span,
            id: ast::DUMMY_NODE_ID,
            is_placeholder: false,
        }
    }

    pub fn arm_unreachable(&self, span: Span) -> ast::Arm {
        self.arm(span, self.pat_wild(span), self.expr_unreachable(span))
    }

    pub fn expr_match(&self, span: Span, arg: P<ast::Expr>, arms: Vec<ast::Arm>) -> P<Expr> {
        self.expr(span, ast::ExprKind::Match(arg, arms))
    }

    pub fn expr_if(
        &self,
        span: Span,
        cond: P<ast::Expr>,
        then: P<ast::Expr>,
        els: Option<P<ast::Expr>>,
    ) -> P<ast::Expr> {
        let els = els.map(|x| self.expr_block(self.block_expr(x)));
        self.expr(span, ast::ExprKind::If(cond, self.block_expr(then), els))
    }

    pub fn lambda_fn_decl(
        &self,
        span: Span,
        fn_decl: P<ast::FnDecl>,
        body: P<ast::Expr>,
        fn_decl_span: Span,
    ) -> P<ast::Expr> {
        self.expr(
            span,
            ast::ExprKind::Closure(
                ast::CaptureBy::Ref,
                ast::Async::No,
                ast::Movability::Movable,
                fn_decl,
                body,
                fn_decl_span,
            ),
        )
    }

    pub fn lambda(&self, span: Span, ids: Vec<Ident>, body: P<ast::Expr>) -> P<ast::Expr> {
        let fn_decl = self.fn_decl(
            ids.iter().map(|id| self.param(span, *id, self.ty(span, ast::TyKind::Infer))).collect(),
            ast::FnRetTy::Default(span),
        );

        // FIXME -- We are using `span` as the span of the `|...|`
        // part of the lambda, but it probably (maybe?) corresponds to
        // the entire lambda body. Probably we should extend the API
        // here, but that's not entirely clear.
        self.expr(
            span,
            ast::ExprKind::Closure(
                ast::CaptureBy::Ref,
                ast::Async::No,
                ast::Movability::Movable,
                fn_decl,
                body,
                span,
            ),
        )
    }

    pub fn lambda0(&self, span: Span, body: P<ast::Expr>) -> P<ast::Expr> {
        self.lambda(span, Vec::new(), body)
    }

    pub fn lambda1(&self, span: Span, body: P<ast::Expr>, ident: Ident) -> P<ast::Expr> {
        self.lambda(span, vec![ident], body)
    }

    pub fn lambda_stmts_1(&self, span: Span, stmts: Vec<ast::Stmt>, ident: Ident) -> P<ast::Expr> {
        self.lambda1(span, self.expr_block(self.block(span, stmts)), ident)
    }

    pub fn param(&self, span: Span, ident: Ident, ty: P<ast::Ty>) -> ast::Param {
        let arg_pat = self.pat_ident(span, ident);
        ast::Param {
            attrs: AttrVec::default(),
            id: ast::DUMMY_NODE_ID,
            pat: arg_pat,
            span,
            ty,
            is_placeholder: false,
        }
    }

    // FIXME: unused `self`
    pub fn fn_decl(&self, inputs: Vec<ast::Param>, output: ast::FnRetTy) -> P<ast::FnDecl> {
        P(ast::FnDecl { inputs, output })
    }

    pub fn item(
        &self,
        span: Span,
        name: Ident,
        attrs: Vec<ast::Attribute>,
        kind: ast::ItemKind,
    ) -> P<ast::Item> {
        // FIXME: Would be nice if our generated code didn't violate
        // Rust coding conventions
        P(ast::Item {
            ident: name,
            attrs,
            id: ast::DUMMY_NODE_ID,
            kind,
            vis: ast::Visibility {
                span: span.shrink_to_lo(),
                kind: ast::VisibilityKind::Inherited,
                tokens: None,
            },
            span,
            tokens: None,
        })
    }

    pub fn variant(&self, span: Span, ident: Ident, tys: Vec<P<ast::Ty>>) -> ast::Variant {
        let vis_span = span.shrink_to_lo();
        let fields: Vec<_> = tys
            .into_iter()
            .map(|ty| ast::StructField {
                span: ty.span,
                ty,
                ident: None,
                vis: ast::Visibility {
                    span: vis_span,
                    kind: ast::VisibilityKind::Inherited,
                    tokens: None,
                },
                attrs: Vec::new(),
                id: ast::DUMMY_NODE_ID,
                is_placeholder: false,
            })
            .collect();

        let vdata = if fields.is_empty() {
            ast::VariantData::Unit(ast::DUMMY_NODE_ID)
        } else {
            ast::VariantData::Tuple(fields, ast::DUMMY_NODE_ID)
        };

        ast::Variant {
            attrs: Vec::new(),
            data: vdata,
            disr_expr: None,
            id: ast::DUMMY_NODE_ID,
            ident,
            vis: ast::Visibility {
                span: vis_span,
                kind: ast::VisibilityKind::Inherited,
                tokens: None,
            },
            span,
            is_placeholder: false,
        }
    }

    pub fn item_static(
        &self,
        span: Span,
        name: Ident,
        ty: P<ast::Ty>,
        mutbl: ast::Mutability,
        expr: P<ast::Expr>,
    ) -> P<ast::Item> {
        self.item(span, name, Vec::new(), ast::ItemKind::Static(ty, mutbl, Some(expr)))
    }

    pub fn item_const(
        &self,
        span: Span,
        name: Ident,
        ty: P<ast::Ty>,
        expr: P<ast::Expr>,
    ) -> P<ast::Item> {
        let def = ast::Defaultness::Final;
        self.item(span, name, Vec::new(), ast::ItemKind::Const(def, ty, Some(expr)))
    }

    pub fn attribute(&self, mi: ast::MetaItem) -> ast::Attribute {
        attr::mk_attr_outer(mi)
    }

    pub fn meta_word(&self, sp: Span, w: Symbol) -> ast::MetaItem {
        attr::mk_word_item(Ident::new(w, sp))
    }
}
