1 use crate::deriving::path_std;
2 use crate::deriving::generic::*;
3 use crate::deriving::generic::ty::*;
5 use rustc_data_structures::thin_vec::ThinVec;
7 use syntax::ast::{self, Ident};
8 use syntax::ast::{Expr, MetaItem};
9 use syntax::ext::base::{Annotatable, ExtCtxt};
10 use syntax::ext::build::AstBuilder;
12 use syntax_pos::{DUMMY_SP, Span};
14 pub fn expand_deriving_debug(cx: &mut ExtCtxt<'_>,
18 push: &mut dyn FnMut(Annotatable)) {
19 // &mut ::std::fmt::Formatter
20 let fmtr = Ptr(Box::new(Literal(path_std!(cx, fmt::Formatter))),
21 Borrowed(None, ast::Mutability::Mutable));
23 let trait_def = TraitDef {
25 attributes: Vec::new(),
26 path: path_std!(cx, fmt::Debug),
27 additional_bounds: Vec::new(),
28 generics: LifetimeBounds::empty(),
30 supports_unions: false,
31 methods: vec![MethodDef {
33 generics: LifetimeBounds::empty(),
34 explicit_self: borrowed_explicit_self(),
35 args: vec![(fmtr, "f")],
36 ret_ty: Literal(path_std!(cx, fmt::Result)),
37 attributes: Vec::new(),
39 unify_fieldless_variants: false,
40 combine_substructure: combine_substructure(Box::new(|a, b, c| {
41 show_substructure(a, b, c)
44 associated_types: Vec::new(),
46 trait_def.expand(cx, mitem, item, push)
49 /// We use the debug builders to do the heavy lifting here
50 fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<Expr> {
51 // build fmt.debug_struct(<name>).field(<fieldname>, &<fieldval>)....build()
52 // or fmt.debug_tuple(<name>).field(&<fieldval>)....build()
53 // based on the "shape".
54 let (ident, vdata, fields) = match substr.fields {
55 Struct(vdata, fields) => (substr.type_ident, *vdata, fields),
56 EnumMatching(_, _, v, fields) => (v.node.ident, &v.node.data, fields),
57 EnumNonMatchingCollapsed(..) |
59 StaticEnum(..) => cx.span_bug(span, "nonsensical .fields in `#[derive(Debug)]`"),
62 // We want to make sure we have the ctxt set so that we can use unstable methods
63 let span = span.with_ctxt(cx.backtrace());
64 let name = cx.expr_lit(span, ast::LitKind::Str(ident.name, ast::StrStyle::Cooked));
65 let builder = Ident::from_str("debug_trait_builder").gensym();
66 let builder_expr = cx.expr_ident(span, builder.clone());
68 let fmt = substr.nonself_args[0].clone();
70 let mut stmts = vec![];
72 ast::VariantData::Tuple(..) | ast::VariantData::Unit(..) => {
73 // tuple struct/"normal" variant
75 cx.expr_method_call(span, fmt, Ident::from_str("debug_tuple"), vec![name]);
76 stmts.push(cx.stmt_let(DUMMY_SP, true, builder, expr));
79 // Use double indirection to make sure this works for unsized types
80 let field = cx.expr_addr_of(field.span, field.self_.clone());
81 let field = cx.expr_addr_of(field.span, field);
83 let expr = cx.expr_method_call(span,
85 Ident::from_str("field"),
88 // Use `let _ = expr;` to avoid triggering the
89 // unused_results lint.
90 stmts.push(stmt_let_undescore(cx, span, expr));
93 ast::VariantData::Struct(..) => {
94 // normal struct/struct variant
96 cx.expr_method_call(span, fmt, Ident::from_str("debug_struct"), vec![name]);
97 stmts.push(cx.stmt_let(DUMMY_SP, true, builder, expr));
100 let name = cx.expr_lit(field.span,
101 ast::LitKind::Str(field.name.unwrap().name,
102 ast::StrStyle::Cooked));
104 // Use double indirection to make sure this works for unsized types
105 let field = cx.expr_addr_of(field.span, field.self_.clone());
106 let field = cx.expr_addr_of(field.span, field);
107 let expr = cx.expr_method_call(span,
108 builder_expr.clone(),
109 Ident::from_str("field"),
111 stmts.push(stmt_let_undescore(cx, span, expr));
116 let expr = cx.expr_method_call(span, builder_expr, Ident::from_str("finish"), vec![]);
118 stmts.push(cx.stmt_expr(expr));
119 let block = cx.block(span, stmts);
123 fn stmt_let_undescore(cx: &mut ExtCtxt<'_>, sp: Span, expr: P<ast::Expr>) -> ast::Stmt {
124 let local = P(ast::Local {
125 pat: cx.pat_wild(sp),
128 id: ast::DUMMY_NODE_ID,
130 attrs: ThinVec::new(),
133 id: ast::DUMMY_NODE_ID,
134 node: ast::StmtKind::Local(local),