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use ast::{MetaItem, Item, Expr};
use ast;
use codemap::Span;
use ext::base::ExtCtxt;
use ext::build::AstBuilder;
use ext::deriving::generic::*;
use ext::deriving::generic::ty::*;
use parse::token::InternedString;
use ptr::P;
pub fn expand_deriving_from_primitive<F>(cx: &mut ExtCtxt,
span: Span,
mitem: &MetaItem,
item: &Item,
push: F) where
F: FnOnce(P<Item>),
{
let inline = cx.meta_word(span, InternedString::new("inline"));
let attrs = vec!(cx.attribute(span, inline));
let trait_def = TraitDef {
span: span,
attributes: Vec::new(),
path: path_std!(cx, core::num::FromPrimitive),
additional_bounds: Vec::new(),
generics: LifetimeBounds::empty(),
methods: vec!(
MethodDef {
name: "from_i64",
generics: LifetimeBounds::empty(),
explicit_self: None,
args: vec!(Literal(path_local!(i64))),
ret_ty: Literal(Path::new_(pathvec_std!(cx, core::option::Option),
None,
vec!(box Self_),
true)),
attributes: attrs.clone(),
combine_substructure: combine_substructure(Box::new(|c, s, sub| {
cs_from("i64", c, s, sub)
})),
},
MethodDef {
name: "from_u64",
generics: LifetimeBounds::empty(),
explicit_self: None,
args: vec!(Literal(path_local!(u64))),
ret_ty: Literal(Path::new_(pathvec_std!(cx, core::option::Option),
None,
vec!(box Self_),
true)),
attributes: attrs,
combine_substructure: combine_substructure(Box::new(|c, s, sub| {
cs_from("u64", c, s, sub)
})),
}
),
associated_types: Vec::new(),
};
trait_def.expand(cx, mitem, item, push)
}
fn cs_from(name: &str, cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
let n = match substr.nonself_args {
[ref n] => n,
_ => cx.span_bug(trait_span, "incorrect number of arguments in `derive(FromPrimitive)`")
};
match *substr.fields {
StaticStruct(..) => {
cx.span_err(trait_span, "`FromPrimitive` cannot be derived for structs");
return cx.expr_fail(trait_span, InternedString::new(""));
}
StaticEnum(enum_def, _) => {
if enum_def.variants.is_empty() {
cx.span_err(trait_span,
"`FromPrimitive` cannot be derived for enums with no variants");
return cx.expr_fail(trait_span, InternedString::new(""));
}
let mut arms = Vec::new();
for variant in &enum_def.variants {
match variant.node.kind {
ast::TupleVariantKind(ref args) => {
if !args.is_empty() {
cx.span_err(trait_span,
"`FromPrimitive` cannot be derived for \
enum variants with arguments");
return cx.expr_fail(trait_span,
InternedString::new(""));
}
let span = variant.span;
let path = cx.path(span, vec![substr.type_ident, variant.node.name]);
let variant = cx.expr_path(path);
let ty = cx.ty_ident(span, cx.ident_of(name));
let cast = cx.expr_cast(span, variant.clone(), ty);
let guard = cx.expr_binary(span, ast::BiEq, n.clone(), cast);
let body = cx.expr_some(span, variant);
let arm = ast::Arm {
attrs: vec!(),
pats: vec!(cx.pat_wild(span)),
guard: Some(guard),
body: body,
};
arms.push(arm);
}
ast::StructVariantKind(_) => {
cx.span_err(trait_span,
"`FromPrimitive` cannot be derived for enums \
with struct variants");
return cx.expr_fail(trait_span,
InternedString::new(""));
}
}
}
let arm = ast::Arm {
attrs: vec!(),
pats: vec!(cx.pat_wild(trait_span)),
guard: None,
body: cx.expr_none(trait_span),
};
arms.push(arm);
cx.expr_match(trait_span, n.clone(), arms)
}
_ => cx.span_bug(trait_span, "expected StaticEnum in derive(FromPrimitive)")
}
}