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|
use crate::deriving::generic::ty::*;
use crate::deriving::generic::*;
use crate::deriving::path_std;
use rustc_ast::{self as ast, MetaItem};
use rustc_expand::base::{Annotatable, ExtCtxt};
use rustc_span::symbol::{sym, Ident, Symbol};
use rustc_span::Span;
pub fn expand_deriving_debug(
cx: &mut ExtCtxt<'_>,
span: Span,
mitem: &MetaItem,
item: &Annotatable,
push: &mut dyn FnMut(Annotatable),
) {
// &mut ::std::fmt::Formatter
let fmtr = Ref(Box::new(Path(path_std!(fmt::Formatter))), ast::Mutability::Mut);
let trait_def = TraitDef {
span,
path: path_std!(fmt::Debug),
additional_bounds: Vec::new(),
generics: Bounds::empty(),
supports_unions: false,
methods: vec![MethodDef {
name: sym::fmt,
generics: Bounds::empty(),
explicit_self: true,
nonself_args: vec![(fmtr, sym::f)],
ret_ty: Path(path_std!(fmt::Result)),
attributes: ast::AttrVec::new(),
unify_fieldless_variants: false,
combine_substructure: combine_substructure(Box::new(|a, b, c| {
show_substructure(a, b, c)
})),
}],
associated_types: Vec::new(),
};
trait_def.expand(cx, mitem, item, push)
}
fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
let (ident, vdata, fields) = match substr.fields {
Struct(vdata, fields) => (substr.type_ident, *vdata, fields),
EnumMatching(_, _, v, fields) => (v.ident, &v.data, fields),
EnumTag(..) | StaticStruct(..) | StaticEnum(..) => {
cx.span_bug(span, "nonsensical .fields in `#[derive(Debug)]`")
}
};
// We want to make sure we have the ctxt set so that we can use unstable methods
let span = cx.with_def_site_ctxt(span);
let name = cx.expr_str(span, ident.name);
let fmt = substr.nonselflike_args[0].clone();
// Struct and tuples are similar enough that we use the same code for both,
// with some extra pieces for structs due to the field names.
let (is_struct, args_per_field) = match vdata {
ast::VariantData::Unit(..) => {
// Special fast path for unit variants.
assert!(fields.is_empty());
(false, 0)
}
ast::VariantData::Tuple(..) => (false, 1),
ast::VariantData::Struct(..) => (true, 2),
};
// The number of fields that can be handled without an array.
const CUTOFF: usize = 5;
if fields.is_empty() {
// Special case for no fields.
let fn_path_write_str = cx.std_path(&[sym::fmt, sym::Formatter, sym::write_str]);
let expr = cx.expr_call_global(span, fn_path_write_str, vec![fmt, name]);
BlockOrExpr::new_expr(expr)
} else if fields.len() <= CUTOFF {
// Few enough fields that we can use a specific-length method.
let debug = if is_struct {
format!("debug_struct_field{}_finish", fields.len())
} else {
format!("debug_tuple_field{}_finish", fields.len())
};
let fn_path_debug = cx.std_path(&[sym::fmt, sym::Formatter, Symbol::intern(&debug)]);
let mut args = Vec::with_capacity(2 + fields.len() * args_per_field);
args.extend([fmt, name]);
for i in 0..fields.len() {
let field = &fields[i];
if is_struct {
let name = cx.expr_str(field.span, field.name.unwrap().name);
args.push(name);
}
// Use an extra indirection to make sure this works for unsized types.
let field = cx.expr_addr_of(field.span, field.self_expr.clone());
args.push(field);
}
let expr = cx.expr_call_global(span, fn_path_debug, args);
BlockOrExpr::new_expr(expr)
} else {
// Enough fields that we must use the any-length method.
let mut name_exprs = Vec::with_capacity(fields.len());
let mut value_exprs = Vec::with_capacity(fields.len());
for field in fields {
if is_struct {
name_exprs.push(cx.expr_str(field.span, field.name.unwrap().name));
}
// Use an extra indirection to make sure this works for unsized types.
let field = cx.expr_addr_of(field.span, field.self_expr.clone());
value_exprs.push(field);
}
// `let names: &'static _ = &["field1", "field2"];`
let names_let = if is_struct {
let lt_static = Some(cx.lifetime_static(span));
let ty_static_ref =
cx.ty_rptr(span, cx.ty_infer(span), lt_static, ast::Mutability::Not);
Some(cx.stmt_let_ty(
span,
false,
Ident::new(sym::names, span),
Some(ty_static_ref),
cx.expr_array_ref(span, name_exprs),
))
} else {
None
};
// `let values: &[&dyn Debug] = &[&&self.field1, &&self.field2];`
let path_debug = cx.path_global(span, cx.std_path(&[sym::fmt, sym::Debug]));
let ty_dyn_debug = cx.ty(
span,
ast::TyKind::TraitObject(vec![cx.trait_bound(path_debug)], ast::TraitObjectSyntax::Dyn),
);
let ty_slice = cx.ty(
span,
ast::TyKind::Slice(cx.ty_rptr(span, ty_dyn_debug, None, ast::Mutability::Not)),
);
let values_let = cx.stmt_let_ty(
span,
false,
Ident::new(sym::values, span),
Some(cx.ty_rptr(span, ty_slice, None, ast::Mutability::Not)),
cx.expr_array_ref(span, value_exprs),
);
// `fmt::Formatter::debug_struct_fields_finish(fmt, name, names, values)` or
// `fmt::Formatter::debug_tuple_fields_finish(fmt, name, values)`
let sym_debug = if is_struct {
sym::debug_struct_fields_finish
} else {
sym::debug_tuple_fields_finish
};
let fn_path_debug_internal = cx.std_path(&[sym::fmt, sym::Formatter, sym_debug]);
let mut args = Vec::with_capacity(4);
args.push(fmt);
args.push(name);
if is_struct {
args.push(cx.expr_ident(span, Ident::new(sym::names, span)));
}
args.push(cx.expr_ident(span, Ident::new(sym::values, span)));
let expr = cx.expr_call_global(span, fn_path_debug_internal, args);
let mut stmts = Vec::with_capacity(3);
if is_struct {
stmts.push(names_let.unwrap());
}
stmts.push(values_let);
BlockOrExpr::new_mixed(stmts, Some(expr))
}
}
|
