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v0: demangle structural constants and &str. #55

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merged 4 commits into from
Aug 24, 2021
Merged

v0: demangle structural constants and &str. #55

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3cf31b9
v0: demangle `str` const values using string literals.
eddyb Jul 30, 2021
245357a
v0: demangle `&` and `&mut` const values.
eddyb Jul 30, 2021
2327898
v0: demangle array and tuple const values.
eddyb Aug 10, 2021
fd906f8
v0: demangle ADT const values.
eddyb Aug 10, 2021
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267 changes: 262 additions & 5 deletions src/v0.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
use core::convert::TryFrom;
use core::{char, fmt, iter, mem};
use core::{char, fmt, iter, mem, str};

#[allow(unused_macros)]
macro_rules! write {
Expand Down Expand Up @@ -287,6 +287,84 @@ impl<'s> HexNibbles<'s> {
}
Some(v)
}

/// Decode a UTF-8 byte sequence (with each byte using a pair of nibbles)
/// into individual `char`s, returning `None` for invalid UTF-8.
fn try_parse_str_chars(&self) -> Option<impl Iterator<Item = char> + 's> {
if self.nibbles.len() % 2 != 0 {
return None;
}

// FIXME(eddyb) use `array_chunks` instead, when that becomes stable.
let mut bytes = self
.nibbles
.as_bytes()
.chunks_exact(2)
.map(|slice| match slice {
[a, b] => [a, b],
_ => unreachable!(),
})
.map(|[&hi, &lo]| {
let half = |nibble: u8| (nibble as char).to_digit(16).unwrap() as u8;
(half(hi) << 4) | half(lo)
});

let chars = iter::from_fn(move || {
// As long as there are any bytes left, there's at least one more
// UTF-8-encoded `char` to decode (or the possibility of error).
bytes.next().map(|first_byte| -> Result<char, ()> {
// FIXME(eddyb) this `enum` and `fn` should be somewhere in `core`.
enum Utf8FirstByteError {
ContinuationByte,
TooLong,
}
fn utf8_len_from_first_byte(byte: u8) -> Result<usize, Utf8FirstByteError> {
match byte {
0x00..=0x7f => Ok(1),
0x80..=0xbf => Err(Utf8FirstByteError::ContinuationByte),
0xc0..=0xdf => Ok(2),
0xe0..=0xef => Ok(3),
0xf0..=0xf7 => Ok(4),
0xf8..=0xff => Err(Utf8FirstByteError::TooLong),
}
}

// Collect the appropriate amount of bytes (up to 4), according
// to the UTF-8 length implied by the first byte.
let utf8_len = utf8_len_from_first_byte(first_byte).map_err(|_| ())?;
let utf8 = &mut [first_byte, 0, 0, 0][..utf8_len];
for i in 1..utf8_len {
utf8[i] = bytes.next().ok_or(())?;
}

// Fully validate the UTF-8 sequence.
let s = str::from_utf8(utf8).map_err(|_| ())?;

// Since we included exactly one UTF-8 sequence, and validation
// succeeded, `str::chars` should return exactly one `char`.
let mut chars = s.chars();
match (chars.next(), chars.next()) {
(Some(c), None) => Ok(c),
_ => unreachable!(
"str::from_utf8({:?}) = {:?} was expected to have 1 char, \
but {} chars were found",
utf8,
s,
s.chars().count()
),
}
})
});

// HACK(eddyb) doing a separate validation iteration like this might be
// wasteful, but it's easier to avoid starting to print a string literal
// in the first place, than to abort it mid-string.
if chars.clone().any(|r| r.is_err()) {
None
} else {
Some(chars.map(Result::unwrap))
}
}
}

fn basic_type(tag: u8) -> Option<&'static str> {
Expand Down Expand Up @@ -815,7 +893,7 @@ impl<'a, 'b, 's> Printer<'a, 'b, 's> {
let lt = parse!(self, integer_62);
self.print_lifetime_from_index(lt)
} else if self.eat(b'K') {
self.print_const()
self.print_const(false)
} else {
self.print_type()
}
Expand Down Expand Up @@ -861,7 +939,7 @@ impl<'a, 'b, 's> Printer<'a, 'b, 's> {
self.print_type()?;
if tag == b'A' {
self.print("; ")?;
self.print_const()?;
self.print_const(true)?;
}
self.print("]")?;
}
Expand Down Expand Up @@ -1001,11 +1079,28 @@ impl<'a, 'b, 's> Printer<'a, 'b, 's> {
Ok(())
}

fn print_const(&mut self) -> fmt::Result {
fn print_const(&mut self, in_value: bool) -> fmt::Result {
let tag = parse!(self, next);

parse!(self, push_depth);

// Only literals (and the names of `const` generic parameters, but they
// don't get mangled at all), can appear in generic argument position
// without any disambiguation, all other expressions require braces.
// To avoid duplicating the mapping between `tag` and what syntax gets
// used (especially any special-casing), every case that needs braces
// has to call `open_brace(self)?` (and the closing brace is automatic).
let mut opened_brace = false;
let mut open_brace_if_outside_expr = |this: &mut Self| {
// If this expression is nested in another, braces aren't required.
if in_value {
return Ok(());
}

opened_brace = true;
this.print("{")
};

match tag {
b'p' => self.print("_")?,

Expand Down Expand Up @@ -1033,13 +1128,82 @@ impl<'a, 'b, 's> Printer<'a, 'b, 's> {
None => invalid!(self),
}
}
b'e' => {
// NOTE(eddyb) a string literal `"..."` has type `&str`, so
// to get back the type `str`, `*"..."` syntax is needed
// (even if that may not be valid in Rust itself).
open_brace_if_outside_expr(self)?;
self.print("*")?;

self.print_const_str_literal()?;
}

b'R' | b'Q' => {
// NOTE(eddyb) this prints `"..."` instead of `&*"..."`, which
// is what `Re..._` would imply (see comment for `str` above).
if tag == b'R' && self.eat(b'e') {
self.print_const_str_literal()?;
} else {
open_brace_if_outside_expr(self)?;
self.print("&")?;
if tag != b'R' {
self.print("mut ")?;
}
self.print_const(true)?;
}
}
b'A' => {
open_brace_if_outside_expr(self)?;
self.print("[")?;
self.print_sep_list(|this| this.print_const(true), ", ")?;
self.print("]")?;
}
b'T' => {
open_brace_if_outside_expr(self)?;
self.print("(")?;
let count = self.print_sep_list(|this| this.print_const(true), ", ")?;
if count == 1 {
self.print(",")?;
}
self.print(")")?;
}
b'V' => {
open_brace_if_outside_expr(self)?;
self.print_path(true)?;
match parse!(self, next) {
b'U' => {}
b'T' => {
self.print("(")?;
self.print_sep_list(|this| this.print_const(true), ", ")?;
self.print(")")?;
}
b'S' => {
self.print(" { ")?;
self.print_sep_list(
|this| {
parse!(this, disambiguator);
let name = parse!(this, ident);
this.print(name)?;
this.print(": ")?;
this.print_const(true)
},
", ",
)?;
self.print(" }")?;
}
_ => invalid!(self),
}
}
b'B' => {
self.print_backref(Self::print_const)?;
self.print_backref(|this| this.print_const(in_value))?;
}
_ => invalid!(self),
}

if opened_brace {
self.print("}")?;
}

self.pop_depth();
Ok(())
}
Expand All @@ -1066,6 +1230,13 @@ impl<'a, 'b, 's> Printer<'a, 'b, 's> {

Ok(())
}

fn print_const_str_literal(&mut self) -> fmt::Result {
match parse!(self, hex_nibbles).try_parse_str_chars() {
Some(chars) => self.print_quoted_escaped_chars('"', chars),
None => invalid!(self),
}
}
}

#[cfg(test)]
Expand Down Expand Up @@ -1164,6 +1335,92 @@ mod tests {
t_const!("c2202_", "'∂'");
}

#[test]
fn demangle_const_str() {
t_const!("e616263_", "{*\"abc\"}");
t_const!("e27_", r#"{*"'"}"#);
t_const!("e090a_", "{*\"\\t\\n\"}");
t_const!("ee28882c3bc_", "{*\"∂ü\"}");
t_const!(
"ee183a1e18390e183ade1839be18394e1839ae18390e183935fe18392e18394e1839b\
e183a0e18398e18394e1839ae183985fe183a1e18390e18393e18398e1839ae18398_",
"{*\"საჭმელად_გემრიელი_სადილი\"}"
);
t_const!(
"ef09f908af09fa688f09fa686f09f90ae20c2a720f09f90b6f09f9192e298\
95f09f94a520c2a720f09fa7a1f09f929bf09f929af09f9299f09f929c_",
"{*\"🐊🦈🦆🐮 § 🐶👒☕🔥 § 🧡💛💚💙💜\"}"
);
}

// NOTE(eddyb) this uses the same strings as `demangle_const_str` and should
// be kept in sync with it - while a macro could be used to generate both
// `str` and `&str` tests, from a single list of strings, this seems clearer.
#[test]
fn demangle_const_ref_str() {
t_const!("Re616263_", "\"abc\"");
t_const!("Re27_", r#""'""#);
t_const!("Re090a_", "\"\\t\\n\"");
t_const!("Ree28882c3bc_", "\"∂ü\"");
t_const!(
"Ree183a1e18390e183ade1839be18394e1839ae18390e183935fe18392e18394e1839b\
e183a0e18398e18394e1839ae183985fe183a1e18390e18393e18398e1839ae18398_",
"\"საჭმელად_გემრიელი_სადილი\""
);
t_const!(
"Ref09f908af09fa688f09fa686f09f90ae20c2a720f09f90b6f09f9192e298\
95f09f94a520c2a720f09fa7a1f09f929bf09f929af09f9299f09f929c_",
"\"🐊🦈🦆🐮 § 🐶👒☕🔥 § 🧡💛💚💙💜\""
);
}

#[test]
fn demangle_const_ref() {
t_const!("Rp", "{&_}");
t_const!("Rh7b_", "{&123}");
t_const!("Rb0_", "{&false}");
t_const!("Rc58_", "{&'X'}");
t_const!("RRRh0_", "{&&&0}");
t_const!("RRRe_", "{&&\"\"}");
t_const!("QAE", "{&mut []}");
}

#[test]
fn demangle_const_array() {
t_const!("AE", "{[]}");
t_const!("Aj0_E", "{[0]}");
t_const!("Ah1_h2_h3_E", "{[1, 2, 3]}");
t_const!("ARe61_Re62_Re63_E", "{[\"a\", \"b\", \"c\"]}");
t_const!("AAh1_h2_EAh3_h4_EE", "{[[1, 2], [3, 4]]}");
}

#[test]
fn demangle_const_tuple() {
t_const!("TE", "{()}");
t_const!("Tj0_E", "{(0,)}");
t_const!("Th1_b0_E", "{(1, false)}");
t_const!(
"TRe616263_c78_RAh1_h2_h3_EE",
"{(\"abc\", 'x', &[1, 2, 3])}"
);
}

#[test]
fn demangle_const_adt() {
t_const!(
"VNvINtNtC4core6option6OptionjE4NoneU",
"{core::option::Option::<usize>::None}"
);
t_const!(
"VNvINtNtC4core6option6OptionjE4SomeTj0_E",
"{core::option::Option::<usize>::Some(0)}"
);
t_const!(
"VNtC3foo3BarS1sRe616263_2chc78_5sliceRAh1_h2_h3_EE",
"{foo::Bar { s: \"abc\", ch: 'x', slice: &[1, 2, 3] }}"
);
}

#[test]
fn demangle_exponential_explosion() {
// NOTE(eddyb) because of the prefix added by `t_nohash_type!` is
Expand Down