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| 1 | +// Copyright 2014 The Rust Project Developers. See the COPYRIGHT |
| 2 | +// file at the top-level directory of this distribution and at |
| 3 | +// http://rust-lang.org/COPYRIGHT. |
| 4 | +// |
| 5 | +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| 6 | +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| 7 | +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| 8 | +// option. This file may not be copied, modified, or distributed |
| 9 | +// except according to those terms. |
| 10 | + |
| 11 | +use ast; |
| 12 | +use ast::{MetaItem, Item, Expr}; |
| 13 | +use codemap::Span; |
| 14 | +use ext::format; |
| 15 | +use ext::base::ExtCtxt; |
| 16 | +use ext::build::AstBuilder; |
| 17 | +use ext::deriving::generic::*; |
| 18 | + |
| 19 | +use parse::token; |
| 20 | + |
| 21 | +use std::hashmap::HashMap; |
| 22 | + |
| 23 | +pub fn expand_deriving_show(cx: &mut ExtCtxt, |
| 24 | + span: Span, |
| 25 | + mitem: @MetaItem, |
| 26 | + in_items: ~[@Item]) |
| 27 | + -> ~[@Item] { |
| 28 | + // &mut ::std::fmt::Formatter |
| 29 | + let fmtr = Ptr(~Literal(Path::new(~["std", "fmt", "Formatter"])), |
| 30 | + Borrowed(None, ast::MutMutable)); |
| 31 | + |
| 32 | + let trait_def = TraitDef { |
| 33 | + cx: cx, span: span, |
| 34 | + |
| 35 | + path: Path::new(~["std", "fmt", "Show"]), |
| 36 | + additional_bounds: ~[], |
| 37 | + generics: LifetimeBounds::empty(), |
| 38 | + methods: ~[ |
| 39 | + MethodDef { |
| 40 | + name: "fmt", |
| 41 | + generics: LifetimeBounds::empty(), |
| 42 | + explicit_self: borrowed_explicit_self(), |
| 43 | + args: ~[fmtr], |
| 44 | + ret_ty: Literal(Path::new(~["std", "fmt", "Result"])), |
| 45 | + inline: false, |
| 46 | + const_nonmatching: false, |
| 47 | + combine_substructure: show_substructure |
| 48 | + } |
| 49 | + ] |
| 50 | + }; |
| 51 | + trait_def.expand(mitem, in_items) |
| 52 | +} |
| 53 | + |
| 54 | +// we construct a format string and then defer to std::fmt, since that |
| 55 | +// knows what's up with formatting at so on. |
| 56 | +fn show_substructure(cx: &mut ExtCtxt, span: Span, |
| 57 | + substr: &Substructure) -> @Expr { |
| 58 | + // build `<name>`, `<name>({}, {}, ...)` or `<name> { <field>: {}, |
| 59 | + // <field>: {}, ... }` based on the "shape". |
| 60 | + // |
| 61 | + // Easy start: they all start with the name. |
| 62 | + let name = match *substr.fields { |
| 63 | + Struct(_) => substr.type_ident, |
| 64 | + EnumMatching(_, v, _) => v.node.name, |
| 65 | + |
| 66 | + EnumNonMatching(..) | StaticStruct(..) | StaticEnum(..) => { |
| 67 | + cx.span_bug(span, "nonsensical .fields in `#[deriving(Show)]`") |
| 68 | + } |
| 69 | + }; |
| 70 | + |
| 71 | + let mut format_string = token::get_ident(name.name).get().to_owned(); |
| 72 | + // the internal fields we're actually formatting |
| 73 | + let mut exprs = ~[]; |
| 74 | + |
| 75 | + // Getting harder... making the format string: |
| 76 | + match *substr.fields { |
| 77 | + // unit struct/nullary variant: no work necessary! |
| 78 | + Struct([]) | EnumMatching(_, _, []) => {} |
| 79 | + |
| 80 | + Struct(ref fields) | EnumMatching(_, _, ref fields) => { |
| 81 | + if fields[0].name.is_none() { |
| 82 | + // tuple struct/"normal" variant |
| 83 | + |
| 84 | + format_string.push_str("("); |
| 85 | + |
| 86 | + for (i, field) in fields.iter().enumerate() { |
| 87 | + if i != 0 { format_string.push_str(", "); } |
| 88 | + |
| 89 | + format_string.push_str("{}"); |
| 90 | + |
| 91 | + exprs.push(field.self_); |
| 92 | + } |
| 93 | + |
| 94 | + format_string.push_str(")"); |
| 95 | + } else { |
| 96 | + // normal struct/struct variant |
| 97 | + |
| 98 | + format_string.push_str(" \\{"); |
| 99 | + |
| 100 | + for (i, field) in fields.iter().enumerate() { |
| 101 | + if i != 0 { format_string.push_str(","); } |
| 102 | + |
| 103 | + let name = token::get_ident(field.name.unwrap().name); |
| 104 | + format_string.push_str(" "); |
| 105 | + format_string.push_str(name.get()); |
| 106 | + format_string.push_str(": {}"); |
| 107 | + |
| 108 | + exprs.push(field.self_); |
| 109 | + } |
| 110 | + |
| 111 | + format_string.push_str(" \\}"); |
| 112 | + } |
| 113 | + } |
| 114 | + _ => unreachable!() |
| 115 | + } |
| 116 | + |
| 117 | + // AST construction! |
| 118 | + // we're basically calling |
| 119 | + // |
| 120 | + // format_arg!(|__args| ::std::fmt::write(fmt.buf, __args), "<format_string>", exprs...) |
| 121 | + // |
| 122 | + // but doing it directly via ext::format. |
| 123 | + let formatter = substr.nonself_args[0]; |
| 124 | + let buf = cx.expr_field_access(span, formatter, cx.ident_of("buf")); |
| 125 | + |
| 126 | + let std_write = ~[cx.ident_of("std"), cx.ident_of("fmt"), cx.ident_of("write")]; |
| 127 | + let args = cx.ident_of("__args"); |
| 128 | + let write_call = cx.expr_call_global(span, std_write, ~[buf, cx.expr_ident(span, args)]); |
| 129 | + let format_closure = cx.lambda_expr(span, ~[args], write_call); |
| 130 | + |
| 131 | + let s = token::intern_and_get_ident(format_string); |
| 132 | + let format_string = cx.expr_str(span, s); |
| 133 | + |
| 134 | + // phew, not our responsibility any more! |
| 135 | + format::expand_preparsed_format_args(cx, span, |
| 136 | + format_closure, |
| 137 | + format_string, exprs, HashMap::new()) |
| 138 | +} |
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