133 lines
5 KiB
Rust
133 lines
5 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use ast::{MetaItem, Item, Expr};
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use ast;
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use codemap::Span;
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use ext::base::ExtCtxt;
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use ext::build::AstBuilder;
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use ext::deriving::generic::*;
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pub fn expand_deriving_from_primitive(cx: &ExtCtxt,
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span: Span,
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mitem: @MetaItem,
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in_items: ~[@Item]) -> ~[@Item] {
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let trait_def = TraitDef {
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cx: cx, span: span,
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path: Path::new(~["std", "num", "FromPrimitive"]),
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additional_bounds: ~[],
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generics: LifetimeBounds::empty(),
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methods: ~[
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MethodDef {
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name: "from_i64",
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generics: LifetimeBounds::empty(),
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explicit_self: None,
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args: ~[
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Literal(Path::new(~["i64"])),
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],
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ret_ty: Literal(Path::new_(~["std", "option", "Option"],
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None,
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~[~Self],
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true)),
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// liable to cause code-bloat
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inline: true,
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const_nonmatching: false,
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combine_substructure: |c, s, sub| cs_from("i64", c, s, sub),
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},
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MethodDef {
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name: "from_u64",
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generics: LifetimeBounds::empty(),
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explicit_self: None,
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args: ~[
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Literal(Path::new(~["u64"])),
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],
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ret_ty: Literal(Path::new_(~["std", "option", "Option"],
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None,
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~[~Self],
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true)),
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// liable to cause code-bloat
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inline: true,
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const_nonmatching: false,
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combine_substructure: |c, s, sub| cs_from("u64", c, s, sub),
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},
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]
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};
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trait_def.expand(mitem, in_items)
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}
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fn cs_from(name: &str, cx: &ExtCtxt, span: Span, substr: &Substructure) -> @Expr {
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let n = match substr.nonself_args {
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[n] => n,
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_ => cx.span_bug(span, "Incorrect number of arguments in `deriving(FromPrimitive)`")
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};
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match *substr.fields {
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StaticStruct(..) => {
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cx.span_err(span, "`FromPrimitive` cannot be derived for structs");
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return cx.expr_fail(span, @"");
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}
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StaticEnum(enum_def, _) => {
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if enum_def.variants.is_empty() {
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cx.span_err(span, "`FromPrimitive` cannot be derived for enums with no variants");
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return cx.expr_fail(span, @"");
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}
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let mut arms = ~[];
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for variant in enum_def.variants.iter() {
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match variant.node.kind {
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ast::TupleVariantKind(ref args) => {
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if !args.is_empty() {
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cx.span_err(span, "`FromPrimitive` cannot be derived for \
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enum variants with arguments");
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return cx.expr_fail(span, @"");
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}
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// expr for `$n == $variant as $name`
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let variant = cx.expr_ident(span, variant.node.name);
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let ty = cx.ty_ident(span, cx.ident_of(name));
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let cast = cx.expr_cast(span, variant, ty);
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let guard = cx.expr_binary(span, ast::BiEq, n, cast);
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// expr for `Some($variant)`
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let body = cx.expr_some(span, variant);
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// arm for `_ if $guard => $body`
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let arm = ast::Arm {
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pats: ~[cx.pat_wild(span)],
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guard: Some(guard),
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body: cx.block_expr(body),
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};
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arms.push(arm);
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}
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ast::StructVariantKind(_) => {
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cx.span_err(span, "`FromPrimitive` cannot be derived for enums \
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with struct variants");
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return cx.expr_fail(span, @"");
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}
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}
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}
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// arm for `_ => None`
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let arm = ast::Arm {
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pats: ~[cx.pat_wild(span)],
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guard: None,
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body: cx.block_expr(cx.expr_none(span)),
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};
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arms.push(arm);
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cx.expr_match(span, n, arms)
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}
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_ => cx.bug("expected StaticEnum in deriving(FromPrimitive)")
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}
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}
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