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|
use super::LoweringContext;
use rustc_ast as ast;
use rustc_ast::visit::{self, Visitor};
use rustc_ast::*;
use rustc_data_structures::fx::FxIndexMap;
use rustc_hir as hir;
use rustc_span::{
sym,
symbol::{kw, Ident},
Span, Symbol,
};
use std::borrow::Cow;
impl<'hir> LoweringContext<'_, 'hir> {
pub(crate) fn lower_format_args(&mut self, sp: Span, fmt: &FormatArgs) -> hir::ExprKind<'hir> {
// Never call the const constructor of `fmt::Arguments` if the
// format_args!() had any arguments _before_ flattening/inlining.
let allow_const = fmt.arguments.all_args().is_empty();
let mut fmt = Cow::Borrowed(fmt);
if self.tcx.sess.opts.unstable_opts.flatten_format_args {
fmt = flatten_format_args(fmt);
fmt = inline_literals(fmt);
}
expand_format_args(self, sp, &fmt, allow_const)
}
}
/// Flattens nested `format_args!()` into one.
///
/// Turns
///
/// `format_args!("a {} {} {}.", 1, format_args!("b{}!", 2), 3)`
///
/// into
///
/// `format_args!("a {} b{}! {}.", 1, 2, 3)`.
fn flatten_format_args(mut fmt: Cow<'_, FormatArgs>) -> Cow<'_, FormatArgs> {
let mut i = 0;
while i < fmt.template.len() {
if let FormatArgsPiece::Placeholder(placeholder) = &fmt.template[i]
&& let FormatTrait::Display | FormatTrait::Debug = &placeholder.format_trait
&& let Ok(arg_index) = placeholder.argument.index
&& let arg = fmt.arguments.all_args()[arg_index].expr.peel_parens_and_refs()
&& let ExprKind::FormatArgs(_) = &arg.kind
// Check that this argument is not used by any other placeholders.
&& fmt.template.iter().enumerate().all(|(j, p)|
i == j ||
!matches!(p, FormatArgsPiece::Placeholder(placeholder)
if placeholder.argument.index == Ok(arg_index))
)
{
// Now we need to mutate the outer FormatArgs.
// If this is the first time, this clones the outer FormatArgs.
let fmt = fmt.to_mut();
// Take the inner FormatArgs out of the outer arguments, and
// replace it by the inner arguments. (We can't just put those at
// the end, because we need to preserve the order of evaluation.)
let args = fmt.arguments.all_args_mut();
let remaining_args = args.split_off(arg_index + 1);
let old_arg_offset = args.len();
let mut fmt2 = &mut args.pop().unwrap().expr; // The inner FormatArgs.
let fmt2 = loop { // Unwrap the Expr to get to the FormatArgs.
match &mut fmt2.kind {
ExprKind::Paren(inner) | ExprKind::AddrOf(BorrowKind::Ref, _, inner) => fmt2 = inner,
ExprKind::FormatArgs(fmt2) => break fmt2,
_ => unreachable!(),
}
};
args.append(fmt2.arguments.all_args_mut());
let new_arg_offset = args.len();
args.extend(remaining_args);
// Correct the indexes that refer to the arguments after the newly inserted arguments.
for_all_argument_indexes(&mut fmt.template, |index| {
if *index >= old_arg_offset {
*index -= old_arg_offset;
*index += new_arg_offset;
}
});
// Now merge the placeholders:
let rest = fmt.template.split_off(i + 1);
fmt.template.pop(); // remove the placeholder for the nested fmt args.
// Insert the pieces from the nested format args, but correct any
// placeholders to point to the correct argument index.
for_all_argument_indexes(&mut fmt2.template, |index| *index += arg_index);
fmt.template.append(&mut fmt2.template);
fmt.template.extend(rest);
// Don't increment `i` here, so we recurse into the newly added pieces.
} else {
i += 1;
}
}
fmt
}
/// Inline literals into the format string.
///
/// Turns
///
/// `format_args!("Hello, {}! {} {}", "World", 123, x)`
///
/// into
///
/// `format_args!("Hello, World! 123 {}", x)`.
fn inline_literals(mut fmt: Cow<'_, FormatArgs>) -> Cow<'_, FormatArgs> {
let mut was_inlined = vec![false; fmt.arguments.all_args().len()];
let mut inlined_anything = false;
for i in 0..fmt.template.len() {
let FormatArgsPiece::Placeholder(placeholder) = &fmt.template[i] else { continue };
let Ok(arg_index) = placeholder.argument.index else { continue };
let mut literal = None;
if let FormatTrait::Display = placeholder.format_trait
&& placeholder.format_options == Default::default()
&& let arg = fmt.arguments.all_args()[arg_index].expr.peel_parens_and_refs()
&& let ExprKind::Lit(lit) = arg.kind
{
if let token::LitKind::Str | token::LitKind::StrRaw(_) = lit.kind
&& let Ok(LitKind::Str(s, _)) = LitKind::from_token_lit(lit)
{
literal = Some(s);
} else if let token::LitKind::Integer = lit.kind
&& let Ok(LitKind::Int(n, _)) = LitKind::from_token_lit(lit)
{
literal = Some(Symbol::intern(&n.to_string()));
}
}
if let Some(literal) = literal {
// Now we need to mutate the outer FormatArgs.
// If this is the first time, this clones the outer FormatArgs.
let fmt = fmt.to_mut();
// Replace the placeholder with the literal.
fmt.template[i] = FormatArgsPiece::Literal(literal);
was_inlined[arg_index] = true;
inlined_anything = true;
}
}
// Remove the arguments that were inlined.
if inlined_anything {
let fmt = fmt.to_mut();
let mut remove = was_inlined;
// Don't remove anything that's still used.
for_all_argument_indexes(&mut fmt.template, |index| remove[*index] = false);
// Drop all the arguments that are marked for removal.
let mut remove_it = remove.iter();
fmt.arguments.all_args_mut().retain(|_| remove_it.next() != Some(&true));
// Calculate the mapping of old to new indexes for the remaining arguments.
let index_map: Vec<usize> = remove
.into_iter()
.scan(0, |i, remove| {
let mapped = *i;
*i += !remove as usize;
Some(mapped)
})
.collect();
// Correct the indexes that refer to arguments that have shifted position.
for_all_argument_indexes(&mut fmt.template, |index| *index = index_map[*index]);
}
fmt
}
#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
enum ArgumentType {
Format(FormatTrait),
Usize,
}
/// Generate a hir expression representing an argument to a format_args invocation.
///
/// Generates:
///
/// ```text
/// <core::fmt::ArgumentV1>::new_…(arg)
/// ```
fn make_argument<'hir>(
ctx: &mut LoweringContext<'_, 'hir>,
sp: Span,
arg: &'hir hir::Expr<'hir>,
ty: ArgumentType,
) -> hir::Expr<'hir> {
use ArgumentType::*;
use FormatTrait::*;
let new_fn = ctx.arena.alloc(ctx.expr_lang_item_type_relative(
sp,
hir::LangItem::FormatArgument,
match ty {
Format(Display) => sym::new_display,
Format(Debug) => sym::new_debug,
Format(LowerExp) => sym::new_lower_exp,
Format(UpperExp) => sym::new_upper_exp,
Format(Octal) => sym::new_octal,
Format(Pointer) => sym::new_pointer,
Format(Binary) => sym::new_binary,
Format(LowerHex) => sym::new_lower_hex,
Format(UpperHex) => sym::new_upper_hex,
Usize => sym::from_usize,
},
));
ctx.expr_call_mut(sp, new_fn, std::slice::from_ref(arg))
}
/// Generate a hir expression for a format_args Count.
///
/// Generates:
///
/// ```text
/// <core::fmt::rt::v1::Count>::Is(…)
/// ```
///
/// or
///
/// ```text
/// <core::fmt::rt::v1::Count>::Param(…)
/// ```
///
/// or
///
/// ```text
/// <core::fmt::rt::v1::Count>::Implied
/// ```
fn make_count<'hir>(
ctx: &mut LoweringContext<'_, 'hir>,
sp: Span,
count: &Option<FormatCount>,
argmap: &mut FxIndexMap<(usize, ArgumentType), Option<Span>>,
) -> hir::Expr<'hir> {
match count {
Some(FormatCount::Literal(n)) => {
let count_is = ctx.arena.alloc(ctx.expr_lang_item_type_relative(
sp,
hir::LangItem::FormatCount,
sym::Is,
));
let value = ctx.arena.alloc_from_iter([ctx.expr_usize(sp, *n)]);
ctx.expr_call_mut(sp, count_is, value)
}
Some(FormatCount::Argument(arg)) => {
if let Ok(arg_index) = arg.index {
let (i, _) = argmap.insert_full((arg_index, ArgumentType::Usize), arg.span);
let count_param = ctx.arena.alloc(ctx.expr_lang_item_type_relative(
sp,
hir::LangItem::FormatCount,
sym::Param,
));
let value = ctx.arena.alloc_from_iter([ctx.expr_usize(sp, i)]);
ctx.expr_call_mut(sp, count_param, value)
} else {
ctx.expr(
sp,
hir::ExprKind::Err(
ctx.tcx.sess.delay_span_bug(sp, "lowered bad format_args count"),
),
)
}
}
None => ctx.expr_lang_item_type_relative(sp, hir::LangItem::FormatCount, sym::Implied),
}
}
/// Generate a hir expression for a format_args placeholder specification.
///
/// Generates
///
/// ```text
/// <core::fmt::rt::v1::Argument::new(
/// …usize, // position
/// '…', // fill
/// <core::fmt::rt::v1::Alignment>::…, // alignment
/// …u32, // flags
/// <core::fmt::rt::v1::Count::…>, // width
/// <core::fmt::rt::v1::Count::…>, // precision
/// )
/// ```
fn make_format_spec<'hir>(
ctx: &mut LoweringContext<'_, 'hir>,
sp: Span,
placeholder: &FormatPlaceholder,
argmap: &mut FxIndexMap<(usize, ArgumentType), Option<Span>>,
) -> hir::Expr<'hir> {
let position = match placeholder.argument.index {
Ok(arg_index) => {
let (i, _) = argmap.insert_full(
(arg_index, ArgumentType::Format(placeholder.format_trait)),
placeholder.span,
);
ctx.expr_usize(sp, i)
}
Err(_) => ctx.expr(
sp,
hir::ExprKind::Err(ctx.tcx.sess.delay_span_bug(sp, "lowered bad format_args count")),
),
};
let &FormatOptions {
ref width,
ref precision,
alignment,
fill,
sign,
alternate,
zero_pad,
debug_hex,
} = &placeholder.format_options;
let fill = ctx.expr_char(sp, fill.unwrap_or(' '));
let align = ctx.expr_lang_item_type_relative(
sp,
hir::LangItem::FormatAlignment,
match alignment {
Some(FormatAlignment::Left) => sym::Left,
Some(FormatAlignment::Right) => sym::Right,
Some(FormatAlignment::Center) => sym::Center,
None => sym::Unknown,
},
);
// This needs to match `FlagV1` in library/core/src/fmt/mod.rs.
let flags: u32 = ((sign == Some(FormatSign::Plus)) as u32)
| ((sign == Some(FormatSign::Minus)) as u32) << 1
| (alternate as u32) << 2
| (zero_pad as u32) << 3
| ((debug_hex == Some(FormatDebugHex::Lower)) as u32) << 4
| ((debug_hex == Some(FormatDebugHex::Upper)) as u32) << 5;
let flags = ctx.expr_u32(sp, flags);
let precision = make_count(ctx, sp, &precision, argmap);
let width = make_count(ctx, sp, &width, argmap);
let format_placeholder_new = ctx.arena.alloc(ctx.expr_lang_item_type_relative(
sp,
hir::LangItem::FormatPlaceholder,
sym::new,
));
let args = ctx.arena.alloc_from_iter([position, fill, align, flags, precision, width]);
ctx.expr_call_mut(sp, format_placeholder_new, args)
}
fn expand_format_args<'hir>(
ctx: &mut LoweringContext<'_, 'hir>,
macsp: Span,
fmt: &FormatArgs,
allow_const: bool,
) -> hir::ExprKind<'hir> {
let mut incomplete_lit = String::new();
let lit_pieces =
ctx.arena.alloc_from_iter(fmt.template.iter().enumerate().filter_map(|(i, piece)| {
match piece {
&FormatArgsPiece::Literal(s) => {
// Coalesce adjacent literal pieces.
if let Some(FormatArgsPiece::Literal(_)) = fmt.template.get(i + 1) {
incomplete_lit.push_str(s.as_str());
None
} else if !incomplete_lit.is_empty() {
incomplete_lit.push_str(s.as_str());
let s = Symbol::intern(&incomplete_lit);
incomplete_lit.clear();
Some(ctx.expr_str(fmt.span, s))
} else {
Some(ctx.expr_str(fmt.span, s))
}
}
&FormatArgsPiece::Placeholder(_) => {
// Inject empty string before placeholders when not already preceded by a literal piece.
if i == 0 || matches!(fmt.template[i - 1], FormatArgsPiece::Placeholder(_)) {
Some(ctx.expr_str(fmt.span, kw::Empty))
} else {
None
}
}
}
}));
let lit_pieces = ctx.expr_array_ref(fmt.span, lit_pieces);
// Whether we'll use the `Arguments::new_v1_formatted` form (true),
// or the `Arguments::new_v1` form (false).
let mut use_format_options = false;
// Create a list of all _unique_ (argument, format trait) combinations.
// E.g. "{0} {0:x} {0} {1}" -> [(0, Display), (0, LowerHex), (1, Display)]
let mut argmap = FxIndexMap::default();
for piece in &fmt.template {
let FormatArgsPiece::Placeholder(placeholder) = piece else { continue };
if placeholder.format_options != Default::default() {
// Can't use basic form if there's any formatting options.
use_format_options = true;
}
if let Ok(index) = placeholder.argument.index {
if argmap
.insert((index, ArgumentType::Format(placeholder.format_trait)), placeholder.span)
.is_some()
{
// Duplicate (argument, format trait) combination,
// which we'll only put once in the args array.
use_format_options = true;
}
}
}
let format_options = use_format_options.then(|| {
// Generate:
// &[format_spec_0, format_spec_1, format_spec_2]
let elements: Vec<_> = fmt
.template
.iter()
.filter_map(|piece| {
let FormatArgsPiece::Placeholder(placeholder) = piece else { return None };
Some(make_format_spec(ctx, macsp, placeholder, &mut argmap))
})
.collect();
ctx.expr_array_ref(macsp, ctx.arena.alloc_from_iter(elements))
});
let arguments = fmt.arguments.all_args();
if allow_const && arguments.is_empty() && argmap.is_empty() {
// Generate:
// <core::fmt::Arguments>::new_const(lit_pieces)
let new = ctx.arena.alloc(ctx.expr_lang_item_type_relative(
macsp,
hir::LangItem::FormatArguments,
sym::new_const,
));
let new_args = ctx.arena.alloc_from_iter([lit_pieces]);
return hir::ExprKind::Call(new, new_args);
}
// If the args array contains exactly all the original arguments once,
// in order, we can use a simple array instead of a `match` construction.
// However, if there's a yield point in any argument except the first one,
// we don't do this, because an ArgumentV1 cannot be kept across yield points.
//
// This is an optimization, speeding up compilation about 1-2% in some cases.
// See https://github.com/rust-lang/rust/pull/106770#issuecomment-1380790609
let use_simple_array = argmap.len() == arguments.len()
&& argmap.iter().enumerate().all(|(i, (&(j, _), _))| i == j)
&& arguments.iter().skip(1).all(|arg| !may_contain_yield_point(&arg.expr));
let args = if use_simple_array {
// Generate:
// &[
// <core::fmt::ArgumentV1>::new_display(&arg0),
// <core::fmt::ArgumentV1>::new_lower_hex(&arg1),
// <core::fmt::ArgumentV1>::new_debug(&arg2),
// …
// ]
let elements: Vec<_> = arguments
.iter()
.zip(argmap)
.map(|(arg, ((_, ty), placeholder_span))| {
let placeholder_span =
placeholder_span.unwrap_or(arg.expr.span).with_ctxt(macsp.ctxt());
let arg_span = match arg.kind {
FormatArgumentKind::Captured(_) => placeholder_span,
_ => arg.expr.span.with_ctxt(macsp.ctxt()),
};
let arg = ctx.lower_expr(&arg.expr);
let ref_arg = ctx.arena.alloc(ctx.expr(
arg_span,
hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Not, arg),
));
make_argument(ctx, placeholder_span, ref_arg, ty)
})
.collect();
ctx.expr_array_ref(macsp, ctx.arena.alloc_from_iter(elements))
} else {
// Generate:
// &match (&arg0, &arg1, &…) {
// args => [
// <core::fmt::ArgumentV1>::new_display(args.0),
// <core::fmt::ArgumentV1>::new_lower_hex(args.1),
// <core::fmt::ArgumentV1>::new_debug(args.0),
// …
// ]
// }
let args_ident = Ident::new(sym::args, macsp);
let (args_pat, args_hir_id) = ctx.pat_ident(macsp, args_ident);
let args = ctx.arena.alloc_from_iter(argmap.iter().map(
|(&(arg_index, ty), &placeholder_span)| {
let arg = &arguments[arg_index];
let placeholder_span =
placeholder_span.unwrap_or(arg.expr.span).with_ctxt(macsp.ctxt());
let arg_span = match arg.kind {
FormatArgumentKind::Captured(_) => placeholder_span,
_ => arg.expr.span.with_ctxt(macsp.ctxt()),
};
let args_ident_expr = ctx.expr_ident(macsp, args_ident, args_hir_id);
let arg = ctx.arena.alloc(ctx.expr(
arg_span,
hir::ExprKind::Field(
args_ident_expr,
Ident::new(sym::integer(arg_index), macsp),
),
));
make_argument(ctx, placeholder_span, arg, ty)
},
));
let elements: Vec<_> = arguments
.iter()
.map(|arg| {
let arg_expr = ctx.lower_expr(&arg.expr);
ctx.expr(
arg.expr.span.with_ctxt(macsp.ctxt()),
hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Not, arg_expr),
)
})
.collect();
let args_tuple = ctx
.arena
.alloc(ctx.expr(macsp, hir::ExprKind::Tup(ctx.arena.alloc_from_iter(elements))));
let array = ctx.arena.alloc(ctx.expr(macsp, hir::ExprKind::Array(args)));
let match_arms = ctx.arena.alloc_from_iter([ctx.arm(args_pat, array)]);
let match_expr = ctx.arena.alloc(ctx.expr_match(
macsp,
args_tuple,
match_arms,
hir::MatchSource::FormatArgs,
));
ctx.expr(
macsp,
hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Not, match_expr),
)
};
if let Some(format_options) = format_options {
// Generate:
// <core::fmt::Arguments>::new_v1_formatted(
// lit_pieces,
// args,
// format_options,
// unsafe { ::core::fmt::UnsafeArg::new() }
// )
let new_v1_formatted = ctx.arena.alloc(ctx.expr_lang_item_type_relative(
macsp,
hir::LangItem::FormatArguments,
sym::new_v1_formatted,
));
let unsafe_arg_new = ctx.arena.alloc(ctx.expr_lang_item_type_relative(
macsp,
hir::LangItem::FormatUnsafeArg,
sym::new,
));
let unsafe_arg_new_call = ctx.expr_call(macsp, unsafe_arg_new, &[]);
let hir_id = ctx.next_id();
let unsafe_arg = ctx.expr_block(ctx.arena.alloc(hir::Block {
stmts: &[],
expr: Some(unsafe_arg_new_call),
hir_id,
rules: hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::CompilerGenerated),
span: macsp,
targeted_by_break: false,
}));
let args = ctx.arena.alloc_from_iter([lit_pieces, args, format_options, unsafe_arg]);
hir::ExprKind::Call(new_v1_formatted, args)
} else {
// Generate:
// <core::fmt::Arguments>::new_v1(
// lit_pieces,
// args,
// )
let new_v1 = ctx.arena.alloc(ctx.expr_lang_item_type_relative(
macsp,
hir::LangItem::FormatArguments,
sym::new_v1,
));
let new_args = ctx.arena.alloc_from_iter([lit_pieces, args]);
hir::ExprKind::Call(new_v1, new_args)
}
}
fn may_contain_yield_point(e: &ast::Expr) -> bool {
struct MayContainYieldPoint(bool);
impl Visitor<'_> for MayContainYieldPoint {
fn visit_expr(&mut self, e: &ast::Expr) {
if let ast::ExprKind::Await(_) | ast::ExprKind::Yield(_) = e.kind {
self.0 = true;
} else {
visit::walk_expr(self, e);
}
}
fn visit_mac_call(&mut self, _: &ast::MacCall) {
// Macros should be expanded at this point.
unreachable!("unexpanded macro in ast lowering");
}
fn visit_item(&mut self, _: &ast::Item) {
// Do not recurse into nested items.
}
}
let mut visitor = MayContainYieldPoint(false);
visitor.visit_expr(e);
visitor.0
}
fn for_all_argument_indexes(template: &mut [FormatArgsPiece], mut f: impl FnMut(&mut usize)) {
for piece in template {
let FormatArgsPiece::Placeholder(placeholder) = piece else { continue };
if let Ok(index) = &mut placeholder.argument.index {
f(index);
}
if let Some(FormatCount::Argument(FormatArgPosition { index: Ok(index), .. })) =
&mut placeholder.format_options.width
{
f(index);
}
if let Some(FormatCount::Argument(FormatArgPosition { index: Ok(index), .. })) =
&mut placeholder.format_options.precision
{
f(index);
}
}
}
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