1 files changed, 336 insertions, 0 deletions
diff --git a/compiler/rustc_ast/src/util/literal.rs b/compiler/rustc_ast/src/util/literal.rs
new file mode 100644
index 000000000..9c18f55c0
--- /dev/null
+++ b/compiler/rustc_ast/src/util/literal.rs
@@ -0,0 +1,336 @@
+//! Code related to parsing literals.
+
+use crate::ast::{self, Lit, LitKind};
+use crate::token::{self, Token};
+
+use rustc_lexer::unescape::{unescape_byte, unescape_char};
+use rustc_lexer::unescape::{unescape_byte_literal, unescape_literal, Mode};
+use rustc_span::symbol::{kw, sym, Symbol};
+use rustc_span::Span;
+
+use std::ascii;
+use tracing::debug;
+
+pub enum LitError {
+    NotLiteral,
+    LexerError,
+    InvalidSuffix,
+    InvalidIntSuffix,
+    InvalidFloatSuffix,
+    NonDecimalFloat(u32),
+    IntTooLarge,
+}
+
+impl LitKind {
+    /// Converts literal token into a semantic literal.
+    pub fn from_lit_token(lit: token::Lit) -> Result<LitKind, LitError> {
+        let token::Lit { kind, symbol, suffix } = lit;
+        if suffix.is_some() && !kind.may_have_suffix() {
+            return Err(LitError::InvalidSuffix);
+        }
+
+        Ok(match kind {
+            token::Bool => {
+                assert!(symbol.is_bool_lit());
+                LitKind::Bool(symbol == kw::True)
+            }
+            token::Byte => {
+                return unescape_byte(symbol.as_str())
+                    .map(LitKind::Byte)
+                    .map_err(|_| LitError::LexerError);
+            }
+            token::Char => {
+                return unescape_char(symbol.as_str())
+                    .map(LitKind::Char)
+                    .map_err(|_| LitError::LexerError);
+            }
+
+            // There are some valid suffixes for integer and float literals,
+            // so all the handling is done internally.
+            token::Integer => return integer_lit(symbol, suffix),
+            token::Float => return float_lit(symbol, suffix),
+
+            token::Str => {
+                // If there are no characters requiring special treatment we can
+                // reuse the symbol from the token. Otherwise, we must generate a
+                // new symbol because the string in the LitKind is different to the
+                // string in the token.
+                let s = symbol.as_str();
+                let symbol = if s.contains(&['\\', '\r']) {
+                    let mut buf = String::with_capacity(s.len());
+                    let mut error = Ok(());
+                    // Force-inlining here is aggressive but the closure is
+                    // called on every char in the string, so it can be
+                    // hot in programs with many long strings.
+                    unescape_literal(
+                        &s,
+                        Mode::Str,
+                        &mut #[inline(always)]
+                        |_, unescaped_char| match unescaped_char {
+                            Ok(c) => buf.push(c),
+                            Err(err) => {
+                                if err.is_fatal() {
+                                    error = Err(LitError::LexerError);
+                                }
+                            }
+                        },
+                    );
+                    error?;
+                    Symbol::intern(&buf)
+                } else {
+                    symbol
+                };
+                LitKind::Str(symbol, ast::StrStyle::Cooked)
+            }
+            token::StrRaw(n) => {
+                // Ditto.
+                let s = symbol.as_str();
+                let symbol =
+                    if s.contains('\r') {
+                        let mut buf = String::with_capacity(s.len());
+                        let mut error = Ok(());
+                        unescape_literal(&s, Mode::RawStr, &mut |_, unescaped_char| {
+                            match unescaped_char {
+                                Ok(c) => buf.push(c),
+                                Err(err) => {
+                                    if err.is_fatal() {
+                                        error = Err(LitError::LexerError);
+                                    }
+                                }
+                            }
+                        });
+                        error?;
+                        Symbol::intern(&buf)
+                    } else {
+                        symbol
+                    };
+                LitKind::Str(symbol, ast::StrStyle::Raw(n))
+            }
+            token::ByteStr => {
+                let s = symbol.as_str();
+                let mut buf = Vec::with_capacity(s.len());
+                let mut error = Ok(());
+                unescape_byte_literal(&s, Mode::ByteStr, &mut |_, unescaped_byte| {
+                    match unescaped_byte {
+                        Ok(c) => buf.push(c),
+                        Err(err) => {
+                            if err.is_fatal() {
+                                error = Err(LitError::LexerError);
+                            }
+                        }
+                    }
+                });
+                error?;
+                LitKind::ByteStr(buf.into())
+            }
+            token::ByteStrRaw(_) => {
+                let s = symbol.as_str();
+                let bytes = if s.contains('\r') {
+                    let mut buf = Vec::with_capacity(s.len());
+                    let mut error = Ok(());
+                    unescape_byte_literal(&s, Mode::RawByteStr, &mut |_, unescaped_byte| {
+                        match unescaped_byte {
+                            Ok(c) => buf.push(c),
+                            Err(err) => {
+                                if err.is_fatal() {
+                                    error = Err(LitError::LexerError);
+                                }
+                            }
+                        }
+                    });
+                    error?;
+                    buf
+                } else {
+                    symbol.to_string().into_bytes()
+                };
+
+                LitKind::ByteStr(bytes.into())
+            }
+            token::Err => LitKind::Err(symbol),
+        })
+    }
+
+    /// Attempts to recover a token from semantic literal.
+    /// This function is used when the original token doesn't exist (e.g. the literal is created
+    /// by an AST-based macro) or unavailable (e.g. from HIR pretty-printing).
+    pub fn to_lit_token(&self) -> token::Lit {
+        let (kind, symbol, suffix) = match *self {
+            LitKind::Str(symbol, ast::StrStyle::Cooked) => {
+                // Don't re-intern unless the escaped string is different.
+                let s = symbol.as_str();
+                let escaped = s.escape_default().to_string();
+                let symbol = if s == escaped { symbol } else { Symbol::intern(&escaped) };
+                (token::Str, symbol, None)
+            }
+            LitKind::Str(symbol, ast::StrStyle::Raw(n)) => (token::StrRaw(n), symbol, None),
+            LitKind::ByteStr(ref bytes) => {
+                let string = bytes
+                    .iter()
+                    .cloned()
+                    .flat_map(ascii::escape_default)
+                    .map(Into::<char>::into)
+                    .collect::<String>();
+                (token::ByteStr, Symbol::intern(&string), None)
+            }
+            LitKind::Byte(byte) => {
+                let string: String = ascii::escape_default(byte).map(Into::<char>::into).collect();
+                (token::Byte, Symbol::intern(&string), None)
+            }
+            LitKind::Char(ch) => {
+                let string: String = ch.escape_default().map(Into::<char>::into).collect();
+                (token::Char, Symbol::intern(&string), None)
+            }
+            LitKind::Int(n, ty) => {
+                let suffix = match ty {
+                    ast::LitIntType::Unsigned(ty) => Some(ty.name()),
+                    ast::LitIntType::Signed(ty) => Some(ty.name()),
+                    ast::LitIntType::Unsuffixed => None,
+                };
+                (token::Integer, sym::integer(n), suffix)
+            }
+            LitKind::Float(symbol, ty) => {
+                let suffix = match ty {
+                    ast::LitFloatType::Suffixed(ty) => Some(ty.name()),
+                    ast::LitFloatType::Unsuffixed => None,
+                };
+                (token::Float, symbol, suffix)
+            }
+            LitKind::Bool(value) => {
+                let symbol = if value { kw::True } else { kw::False };
+                (token::Bool, symbol, None)
+            }
+            LitKind::Err(symbol) => (token::Err, symbol, None),
+        };
+
+        token::Lit::new(kind, symbol, suffix)
+    }
+}
+
+impl Lit {
+    /// Converts literal token into an AST literal.
+    pub fn from_lit_token(token: token::Lit, span: Span) -> Result<Lit, LitError> {
+        Ok(Lit { token, kind: LitKind::from_lit_token(token)?, span })
+    }
+
+    /// Converts arbitrary token into an AST literal.
+    ///
+    /// Keep this in sync with `Token::can_begin_literal_or_bool` excluding unary negation.
+    pub fn from_token(token: &Token) -> Result<Lit, LitError> {
+        let lit = match token.uninterpolate().kind {
+            token::Ident(name, false) if name.is_bool_lit() => {
+                token::Lit::new(token::Bool, name, None)
+            }
+            token::Literal(lit) => lit,
+            token::Interpolated(ref nt) => {
+                if let token::NtExpr(expr) | token::NtLiteral(expr) = &**nt
+                    && let ast::ExprKind::Lit(lit) = &expr.kind
+                {
+                    return Ok(lit.clone());
+                }
+                return Err(LitError::NotLiteral);
+            }
+            _ => return Err(LitError::NotLiteral),
+        };
+
+        Lit::from_lit_token(lit, token.span)
+    }
+
+    /// Attempts to recover an AST literal from semantic literal.
+    /// This function is used when the original token doesn't exist (e.g. the literal is created
+    /// by an AST-based macro) or unavailable (e.g. from HIR pretty-printing).
+    pub fn from_lit_kind(kind: LitKind, span: Span) -> Lit {
+        Lit { token: kind.to_lit_token(), kind, span }
+    }
+
+    /// Losslessly convert an AST literal into a token.
+    pub fn to_token(&self) -> Token {
+        let kind = match self.token.kind {
+            token::Bool => token::Ident(self.token.symbol, false),
+            _ => token::Literal(self.token),
+        };
+        Token::new(kind, self.span)
+    }
+}
+
+fn strip_underscores(symbol: Symbol) -> Symbol {
+    // Do not allocate a new string unless necessary.
+    let s = symbol.as_str();
+    if s.contains('_') {
+        let mut s = s.to_string();
+        s.retain(|c| c != '_');
+        return Symbol::intern(&s);
+    }
+    symbol
+}
+
+fn filtered_float_lit(
+    symbol: Symbol,
+    suffix: Option<Symbol>,
+    base: u32,
+) -> Result<LitKind, LitError> {
+    debug!("filtered_float_lit: {:?}, {:?}, {:?}", symbol, suffix, base);
+    if base != 10 {
+        return Err(LitError::NonDecimalFloat(base));
+    }
+    Ok(match suffix {
+        Some(suf) => LitKind::Float(
+            symbol,
+            ast::LitFloatType::Suffixed(match suf {
+                sym::f32 => ast::FloatTy::F32,
+                sym::f64 => ast::FloatTy::F64,
+                _ => return Err(LitError::InvalidFloatSuffix),
+            }),
+        ),
+        None => LitKind::Float(symbol, ast::LitFloatType::Unsuffixed),
+    })
+}
+
+fn float_lit(symbol: Symbol, suffix: Option<Symbol>) -> Result<LitKind, LitError> {
+    debug!("float_lit: {:?}, {:?}", symbol, suffix);
+    filtered_float_lit(strip_underscores(symbol), suffix, 10)
+}
+
+fn integer_lit(symbol: Symbol, suffix: Option<Symbol>) -> Result<LitKind, LitError> {
+    debug!("integer_lit: {:?}, {:?}", symbol, suffix);
+    let symbol = strip_underscores(symbol);
+    let s = symbol.as_str();
+
+    let base = match s.as_bytes() {
+        [b'0', b'x', ..] => 16,
+        [b'0', b'o', ..] => 8,
+        [b'0', b'b', ..] => 2,
+        _ => 10,
+    };
+
+    let ty = match suffix {
+        Some(suf) => match suf {
+            sym::isize => ast::LitIntType::Signed(ast::IntTy::Isize),
+            sym::i8 => ast::LitIntType::Signed(ast::IntTy::I8),
+            sym::i16 => ast::LitIntType::Signed(ast::IntTy::I16),
+            sym::i32 => ast::LitIntType::Signed(ast::IntTy::I32),
+            sym::i64 => ast::LitIntType::Signed(ast::IntTy::I64),
+            sym::i128 => ast::LitIntType::Signed(ast::IntTy::I128),
+            sym::usize => ast::LitIntType::Unsigned(ast::UintTy::Usize),
+            sym::u8 => ast::LitIntType::Unsigned(ast::UintTy::U8),
+            sym::u16 => ast::LitIntType::Unsigned(ast::UintTy::U16),
+            sym::u32 => ast::LitIntType::Unsigned(ast::UintTy::U32),
+            sym::u64 => ast::LitIntType::Unsigned(ast::UintTy::U64),
+            sym::u128 => ast::LitIntType::Unsigned(ast::UintTy::U128),
+            // `1f64` and `2f32` etc. are valid float literals, and
+            // `fxxx` looks more like an invalid float literal than invalid integer literal.
+            _ if suf.as_str().starts_with('f') => return filtered_float_lit(symbol, suffix, base),
+            _ => return Err(LitError::InvalidIntSuffix),
+        },
+        _ => ast::LitIntType::Unsuffixed,
+    };
+
+    let s = &s[if base != 10 { 2 } else { 0 }..];
+    u128::from_str_radix(s, base).map(|i| LitKind::Int(i, ty)).map_err(|_| {
+        // Small bases are lexed as if they were base 10, e.g, the string
+        // might be `0b10201`. This will cause the conversion above to fail,
+        // but these kinds of errors are already reported by the lexer.
+        let from_lexer =
+            base < 10 && s.chars().any(|c| c.to_digit(10).map_or(false, |d| d >= base));
+        if from_lexer { LitError::LexerError } else { LitError::IntTooLarge }
+    })
+}