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use ast;
use ast::{MetaItem, Item, Expr,};
use codemap::Span;
use ext::format;
use ext::base::ExtCtxt;
use ext::build::AstBuilder;
use ext::deriving::generic::*;
use ext::deriving::generic::ty::*;
use parse::token;
use ptr::P;
use std::collections::HashMap;
pub fn expand_deriving_show<F>(cx: &mut ExtCtxt,
span: Span,
mitem: &MetaItem,
item: &Item,
push: F) where
F: FnOnce(P<Item>),
{
let fmtr = Ptr(box Literal(Path::new(vec!("std", "fmt", "Formatter"))),
Borrowed(None, ast::MutMutable));
let trait_def = TraitDef {
span: span,
attributes: Vec::new(),
path: Path::new(vec!("std", "fmt", "Show")),
additional_bounds: Vec::new(),
generics: LifetimeBounds::empty(),
methods: vec!(
MethodDef {
name: "fmt",
generics: LifetimeBounds::empty(),
explicit_self: borrowed_explicit_self(),
args: vec!(fmtr),
ret_ty: Literal(Path::new(vec!("std", "fmt", "Result"))),
attributes: Vec::new(),
combine_substructure: combine_substructure(|a, b, c| {
show_substructure(a, b, c)
})
}
)
};
trait_def.expand(cx, mitem, item, push)
}
fn show_substructure(cx: &mut ExtCtxt, span: Span,
substr: &Substructure) -> P<Expr> {
let name = match *substr.fields {
Struct(_) => substr.type_ident,
EnumMatching(_, v, _) => v.node.name,
EnumNonMatchingCollapsed(..) | StaticStruct(..) | StaticEnum(..) => {
cx.span_bug(span, "nonsensical .fields in `#[deriving(Show)]`")
}
};
let mut format_string = String::from_str(token::get_ident(name).get());
let mut exprs = Vec::new();
match *substr.fields {
Struct(ref fields) if fields.len() == 0 => {}
EnumMatching(_, _, ref fields) if fields.len() == 0 => {}
Struct(ref fields) | EnumMatching(_, _, ref fields) => {
if fields[0].name.is_none() {
format_string.push_str("(");
for (i, field) in fields.iter().enumerate() {
if i != 0 { format_string.push_str(", "); }
format_string.push_str("{}");
exprs.push(field.self_.clone());
}
format_string.push_str(")");
} else {
format_string.push_str(" {{");
for (i, field) in fields.iter().enumerate() {
if i != 0 { format_string.push_str(","); }
let name = token::get_ident(field.name.unwrap());
format_string.push_str(" ");
format_string.push_str(name.get());
format_string.push_str(": {}");
exprs.push(field.self_.clone());
}
format_string.push_str(" }}");
}
}
_ => unreachable!()
}
let formatter = substr.nonself_args[0].clone();
let meth = cx.ident_of("write_fmt");
let s = token::intern_and_get_ident(format_string[]);
let format_string = cx.expr_str(span, s);
let args = vec![
format::expand_preparsed_format_args(cx, span, format_string,
exprs, vec![], HashMap::new())
];
cx.expr_method_call(span, formatter, meth, args)
}