src/libsyntax/ext/deriving/show.rs

   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, Expr,};
  13 use codemap::Span;
  14 use ext::base::{ExtCtxt, Annotatable};
  15 use ext::build::AstBuilder;
  16 use ext::deriving::generic::*;
  17 use ext::deriving::generic::ty::*;
  18 use parse::token;
  19 use ptr::P;
  20
  21 pub fn expand_deriving_show(cx: &mut ExtCtxt,
  22                             span: Span,
  23                             mitem: &MetaItem,
  24                             item: &Annotatable,
  25                             push: &mut FnMut(Annotatable))
  26 {
  27     // &mut ::std::fmt::Formatter
  28     let fmtr = Ptr(Box::new(Literal(path_std!(cx, core::fmt::Formatter))),
  29                    Borrowed(None, ast::MutMutable));
  30
  31     let trait_def = TraitDef {
  32         span: span,
  33         attributes: Vec::new(),
  34         path: path_std!(cx, core::fmt::Debug),
  35         additional_bounds: Vec::new(),
  36         generics: LifetimeBounds::empty(),
  37         methods: vec![
  38             MethodDef {
  39                 name: "fmt",
  40                 generics: LifetimeBounds::empty(),
  41                 explicit_self: borrowed_explicit_self(),
  42                 args: vec!(fmtr),
  43                 ret_ty: Literal(path_std!(cx, core::fmt::Result)),
  44                 attributes: Vec::new(),
  45                 is_unsafe: false,
  46                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
  47                     show_substructure(a, b, c)
  48                 }))
  49             }
  50         ],
  51         associated_types: Vec::new(),
  52     };
  53     trait_def.expand(cx, mitem, item, push)
  54 }
  55
  56 /// We use the debug builders to do the heavy lifting here
  57 fn show_substructure(cx: &mut ExtCtxt, span: Span,
  58                      substr: &Substructure) -> P<Expr> {
  59     // build fmt.debug_struct(<name>).field(<fieldname>, &<fieldval>)....build()
  60     // or fmt.debug_tuple(<name>).field(&<fieldval>)....build()
  61     // based on the "shape".
  62     let ident = match *substr.fields {
  63         Struct(_) => substr.type_ident,
  64         EnumMatching(_, v, _) => v.node.name,
  65         EnumNonMatchingCollapsed(..) | StaticStruct(..) | StaticEnum(..) => {
  66             cx.span_bug(span, "nonsensical .fields in `#[derive(Debug)]`")
  67         }
  68     };
  69
  70     // We want to make sure we have the expn_id set so that we can use unstable methods
  71     let span = Span { expn_id: cx.backtrace(), .. span };
  72     let name = cx.expr_lit(span, ast::Lit_::LitStr(ident.name.as_str(),
  73                                                    ast::StrStyle::CookedStr));
  74     let mut expr = substr.nonself_args[0].clone();
  75
  76     match *substr.fields {
  77         Struct(ref fields) | EnumMatching(_, _, ref fields) => {
  78
  79             if fields.is_empty() || fields[0].name.is_none() {
  80                 // tuple struct/"normal" variant
  81                 expr = cx.expr_method_call(span,
  82                                            expr,
  83                                            token::str_to_ident("debug_tuple"),
  84                                            vec![name]);
  85
  86                 for field in fields {
  87                     // Use double indirection to make sure this works for unsized types
  88                     let field = cx.expr_addr_of(field.span, field.self_.clone());
  89                     let field = cx.expr_addr_of(field.span, field);
  90
  91                     expr = cx.expr_method_call(span,
  92                                                expr,
  93                                                token::str_to_ident("field"),
  94                                                vec![field]);
  95                 }
  96             } else {
  97                 // normal struct/struct variant
  98                 expr = cx.expr_method_call(span,
  99                                            expr,
 100                                            token::str_to_ident("debug_struct"),
 101                                            vec![name]);
 102
 103                 for field in fields {
 104                     let name = cx.expr_lit(field.span, ast::Lit_::LitStr(
 105                             field.name.unwrap().name.as_str(),
 106                             ast::StrStyle::CookedStr));
 107
 108                     // Use double indirection to make sure this works for unsized types
 109                     let field = cx.expr_addr_of(field.span, field.self_.clone());
 110                     let field = cx.expr_addr_of(field.span, field);
 111                     expr = cx.expr_method_call(span,
 112                                                expr,
 113                                                token::str_to_ident("field"),
 114                                                vec![name, field]);
 115                 }
 116             }
 117         }
 118         _ => unreachable!()
 119     }
 120
 121     cx.expr_method_call(span,
 122                         expr,
 123                         token::str_to_ident("finish"),
 124                         vec![])
 125 }