Auto merge of #62902 - Mark-Simulacrum:rollup-mxfk0mm, r=Mark-Simulacrum

Rollup of 14 pull requests

Successful merges:

 - #60951 (more specific errors in src/librustc/mir/interpret/error.rs)
 - #62523 (Delay bug to resolve HRTB ICE)
 - #62656 (explain how to search in slice without owned data)
 - #62791 (Handle more cases of typos misinterpreted as type ascription)
 - #62804 (rustc_typeck: improve diagnostics for _ const/static declarations)
 - #62808 (Revert "Disable stack probing for gnux32.")
 - #62817 (Tweak span for variant not found error)
 - #62842 (Add tests for issue-58887)
 - #62851 (move unescape module to rustc_lexer)
 - #62859 (Place::as_place_ref is now Place::as_ref)
 - #62869 (add rustc_private as a proper language feature gate)
 - #62880 (normalize use of backticks in compiler messages for librustc_allocator)
 - #62885 (Change "OSX" to "macOS")
 - #62889 (Update stage0.txt)

Failed merges:

r? @ghost

7 files changed, 78 insertions, 674 deletions

diff --git a/src/libsyntax/parse/diagnostics.rs b/src/libsyntax/parse/diagnostics.rs
index 0e88a0ee289..f4fc87506f3 100644
--- a/src/libsyntax/parse/diagnostics.rs
+++ b/src/libsyntax/parse/diagnostics.rs
@@ -2,6 +2,7 @@ use crate::ast::{
     self, Arg, BinOpKind, BindingMode, BlockCheckMode, Expr, ExprKind, Ident, Item, ItemKind,
     Mutability, Pat, PatKind, PathSegment, QSelf, Ty, TyKind, VariantData,
 };
+use crate::feature_gate::{feature_err, UnstableFeatures};
 use crate::parse::{SeqSep, PResult, Parser, ParseSess};
 use crate::parse::parser::{BlockMode, PathStyle, SemiColonMode, TokenType, TokenExpectType};
 use crate::parse::token::{self, TokenKind};
@@ -326,8 +327,8 @@ impl<'a> Parser<'a> {
             self.token.is_keyword(kw::Return) ||
             self.token.is_keyword(kw::While)
         );
-        let cm = self.sess.source_map();
-        match (cm.lookup_line(self.token.span.lo()), cm.lookup_line(sp.lo())) {
+        let sm = self.sess.source_map();
+        match (sm.lookup_line(self.token.span.lo()), sm.lookup_line(sp.lo())) {
             (Ok(ref a), Ok(ref b)) if a.line != b.line && is_semi_suggestable => {
                 // The spans are in different lines, expected `;` and found `let` or `return`.
                 // High likelihood that it is only a missing `;`.
@@ -365,9 +366,53 @@ impl<'a> Parser<'a> {
                 err.span_label(self.token.span, "unexpected token");
             }
         }
+        self.maybe_annotate_with_ascription(&mut err, false);
         Err(err)
     }
 
+    pub fn maybe_annotate_with_ascription(
+        &self,
+        err: &mut DiagnosticBuilder<'_>,
+        maybe_expected_semicolon: bool,
+    ) {
+        if let Some((sp, likely_path)) = self.last_type_ascription {
+            let sm = self.sess.source_map();
+            let next_pos = sm.lookup_char_pos(self.token.span.lo());
+            let op_pos = sm.lookup_char_pos(sp.hi());
+
+            if likely_path {
+                err.span_suggestion(
+                    sp,
+                    "maybe write a path separator here",
+                    "::".to_string(),
+                    match self.sess.unstable_features {
+                        UnstableFeatures::Disallow => Applicability::MachineApplicable,
+                        _ => Applicability::MaybeIncorrect,
+                    },
+                );
+            } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
+                err.span_suggestion(
+                    sp,
+                    "try using a semicolon",
+                    ";".to_string(),
+                    Applicability::MaybeIncorrect,
+                );
+            } else if let UnstableFeatures::Disallow = self.sess.unstable_features {
+                err.span_label(sp, "tried to parse a type due to this");
+            } else {
+                err.span_label(sp, "tried to parse a type due to this type ascription");
+            }
+            if let UnstableFeatures::Disallow = self.sess.unstable_features {
+                // Give extra information about type ascription only if it's a nightly compiler.
+            } else {
+                err.note("`#![feature(type_ascription)]` lets you annotate an expression with a \
+                          type: `<expr>: <type>`");
+                err.note("for more information, see \
+                          https://github.com/rust-lang/rust/issues/23416");
+            }
+        }
+    }
+
     /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
     /// passes through any errors encountered. Used for error recovery.
     crate fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
@@ -556,7 +601,7 @@ impl<'a> Parser<'a> {
         .collect::<Vec<_>>();
 
         if !discriminant_spans.is_empty() && has_fields {
-            let mut err = crate::feature_gate::feature_err(
+            let mut err = feature_err(
                 sess,
                 sym::arbitrary_enum_discriminant,
                 discriminant_spans.clone(),
@@ -769,8 +814,8 @@ impl<'a> Parser<'a> {
                 return Ok(recovered);
             }
         }
-        let cm = self.sess.source_map();
-        match (cm.lookup_line(prev_sp.lo()), cm.lookup_line(sp.lo())) {
+        let sm = self.sess.source_map();
+        match (sm.lookup_line(prev_sp.lo()), sm.lookup_line(sp.lo())) {
             (Ok(ref a), Ok(ref b)) if a.line == b.line => {
                 // When the spans are in the same line, it means that the only content
                 // between them is whitespace, point only at the found token.
@@ -887,47 +932,9 @@ impl<'a> Parser<'a> {
             self.look_ahead(2, |t| t.is_ident()) ||
             self.look_ahead(1, |t| t == &token::Colon) &&  // `foo:bar:baz`
             self.look_ahead(2, |t| t.is_ident()) ||
-            self.look_ahead(1, |t| t == &token::ModSep) &&  // `foo:bar::baz`
-            self.look_ahead(2, |t| t.is_ident())
-    }
-
-    crate fn bad_type_ascription(
-        &self,
-        err: &mut DiagnosticBuilder<'a>,
-        lhs_span: Span,
-        cur_op_span: Span,
-        next_sp: Span,
-        maybe_path: bool,
-    ) {
-        err.span_label(self.token.span, "expecting a type here because of type ascription");
-        let cm = self.sess.source_map();
-        let next_pos = cm.lookup_char_pos(next_sp.lo());
-        let op_pos = cm.lookup_char_pos(cur_op_span.hi());
-        if op_pos.line != next_pos.line {
-            err.span_suggestion(
-                cur_op_span,
-                "try using a semicolon",
-                ";".to_string(),
-                Applicability::MaybeIncorrect,
-            );
-        } else {
-            if maybe_path {
-                err.span_suggestion(
-                    cur_op_span,
-                    "maybe you meant to write a path separator here",
-                    "::".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            } else {
-                err.note("`#![feature(type_ascription)]` lets you annotate an \
-                          expression with a type: `<expr>: <type>`")
-                    .span_note(
-                        lhs_span,
-                        "this expression expects an ascribed type after the colon",
-                    )
-                    .help("this might be indicative of a syntax error elsewhere");
-            }
-        }
+            self.look_ahead(1, |t| t == &token::ModSep) &&
+            (self.look_ahead(2, |t| t.is_ident()) ||   // `foo:bar::baz`
+             self.look_ahead(2, |t| t == &token::Lt))  // `foo:bar::<baz>`
     }
 
     crate fn recover_seq_parse_error(
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index bfefd9adbfe..b97801a50d4 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -1,12 +1,12 @@
 use crate::parse::ParseSess;
 use crate::parse::token::{self, Token, TokenKind};
 use crate::symbol::{sym, Symbol};
-use crate::parse::unescape;
 use crate::parse::unescape_error_reporting::{emit_unescape_error, push_escaped_char};
 
 use errors::{FatalError, Diagnostic, DiagnosticBuilder};
 use syntax_pos::{BytePos, Pos, Span, NO_EXPANSION};
 use rustc_lexer::Base;
+use rustc_lexer::unescape;
 
 use std::borrow::Cow;
 use std::char;
diff --git a/src/libsyntax/parse/literal.rs b/src/libsyntax/parse/literal.rs
index 683d1641565..6409acba573 100644
--- a/src/libsyntax/parse/literal.rs
+++ b/src/libsyntax/parse/literal.rs
@@ -4,9 +4,6 @@ use crate::ast::{self, Lit, LitKind};
 use crate::parse::parser::Parser;
 use crate::parse::PResult;
 use crate::parse::token::{self, Token, TokenKind};
-use crate::parse::unescape::{unescape_char, unescape_byte};
-use crate::parse::unescape::{unescape_str, unescape_byte_str};
-use crate::parse::unescape::{unescape_raw_str, unescape_raw_byte_str};
 use crate::print::pprust;
 use crate::symbol::{kw, sym, Symbol};
 use crate::tokenstream::{TokenStream, TokenTree};
@@ -15,6 +12,9 @@ use errors::{Applicability, Handler};
 use log::debug;
 use rustc_data_structures::sync::Lrc;
 use syntax_pos::Span;
+use rustc_lexer::unescape::{unescape_char, unescape_byte};
+use rustc_lexer::unescape::{unescape_str, unescape_byte_str};
+use rustc_lexer::unescape::{unescape_raw_str, unescape_raw_byte_str};
 
 use std::ascii;
 
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 4c4551b1757..225065c1cf1 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -32,7 +32,6 @@ pub mod token;
 crate mod classify;
 crate mod diagnostics;
 crate mod literal;
-crate mod unescape;
 crate mod unescape_error_reporting;
 
 /// Info about a parsing session.
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 1d4d02c7325..da388694637 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -239,6 +239,7 @@ pub struct Parser<'a> {
     /// error.
     crate unclosed_delims: Vec<UnmatchedBrace>,
     crate last_unexpected_token_span: Option<Span>,
+    crate last_type_ascription: Option<(Span, bool /* likely path typo */)>,
     /// If present, this `Parser` is not parsing Rust code but rather a macro call.
     crate subparser_name: Option<&'static str>,
 }
@@ -502,6 +503,7 @@ impl<'a> Parser<'a> {
             max_angle_bracket_count: 0,
             unclosed_delims: Vec::new(),
             last_unexpected_token_span: None,
+            last_type_ascription: None,
             subparser_name,
         };
 
@@ -1422,7 +1424,10 @@ impl<'a> Parser<'a> {
             }
         } else {
             let msg = format!("expected type, found {}", self.this_token_descr());
-            return Err(self.fatal(&msg));
+            let mut err = self.fatal(&msg);
+            err.span_label(self.token.span, "expected type");
+            self.maybe_annotate_with_ascription(&mut err, true);
+            return Err(err);
         };
 
         let span = lo.to(self.prev_span);
@@ -2823,10 +2828,11 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses an associative expression with operators of at least `min_prec` precedence.
-    fn parse_assoc_expr_with(&mut self,
-                                 min_prec: usize,
-                                 lhs: LhsExpr)
-                                 -> PResult<'a, P<Expr>> {
+    fn parse_assoc_expr_with(
+        &mut self,
+        min_prec: usize,
+        lhs: LhsExpr,
+    ) -> PResult<'a, P<Expr>> {
         let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
             expr
         } else {
@@ -2840,9 +2846,11 @@ impl<'a> Parser<'a> {
                 self.parse_prefix_expr(attrs)?
             }
         };
+        let last_type_ascription_set = self.last_type_ascription.is_some();
 
         match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
             (true, None) => {
+                self.last_type_ascription = None;
                 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
                 return Ok(lhs);
             }
@@ -2857,12 +2865,14 @@ impl<'a> Parser<'a> {
             // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
             // `if x { a } else { b } && if y { c } else { d }`
             if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
+                self.last_type_ascription = None;
                 // These cases are ambiguous and can't be identified in the parser alone
                 let sp = self.sess.source_map().start_point(self.token.span);
                 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
                 return Ok(lhs);
             }
             (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
+                self.last_type_ascription = None;
                 return Ok(lhs);
             }
             (true, Some(_)) => {
@@ -2921,21 +2931,9 @@ impl<'a> Parser<'a> {
                 continue
             } else if op == AssocOp::Colon {
                 let maybe_path = self.could_ascription_be_path(&lhs.node);
-                let next_sp = self.token.span;
+                self.last_type_ascription = Some((self.prev_span, maybe_path));
 
-                lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
-                    Ok(lhs) => lhs,
-                    Err(mut err) => {
-                        self.bad_type_ascription(
-                            &mut err,
-                            lhs_span,
-                            cur_op_span,
-                            next_sp,
-                            maybe_path,
-                        );
-                        return Err(err);
-                    }
-                };
+                lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
                 continue
             } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
                 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
@@ -3020,6 +3018,9 @@ impl<'a> Parser<'a> {
 
             if let Fixity::None = fixity { break }
         }
+        if last_type_ascription_set {
+            self.last_type_ascription = None;
+        }
         Ok(lhs)
     }
 
diff --git a/src/libsyntax/parse/unescape.rs b/src/libsyntax/parse/unescape.rs
deleted file mode 100644
index 87cc9c1c9e3..00000000000
--- a/src/libsyntax/parse/unescape.rs
+++ /dev/null
@@ -1,602 +0,0 @@
-//! Utilities for validating string and char literals and turning them into
-//! values they represent.
-
-use std::str::Chars;
-use std::ops::Range;
-
-#[derive(Debug, PartialEq, Eq)]
-pub(crate) enum EscapeError {
-    ZeroChars,
-    MoreThanOneChar,
-
-    LoneSlash,
-    InvalidEscape,
-    BareCarriageReturn,
-    BareCarriageReturnInRawString,
-    EscapeOnlyChar,
-
-    TooShortHexEscape,
-    InvalidCharInHexEscape,
-    OutOfRangeHexEscape,
-
-    NoBraceInUnicodeEscape,
-    InvalidCharInUnicodeEscape,
-    EmptyUnicodeEscape,
-    UnclosedUnicodeEscape,
-    LeadingUnderscoreUnicodeEscape,
-    OverlongUnicodeEscape,
-    LoneSurrogateUnicodeEscape,
-    OutOfRangeUnicodeEscape,
-
-    UnicodeEscapeInByte,
-    NonAsciiCharInByte,
-    NonAsciiCharInByteString,
-}
-
-/// Takes a contents of a char literal (without quotes), and returns an
-/// unescaped char or an error
-pub(crate) fn unescape_char(literal_text: &str) -> Result<char, (usize, EscapeError)> {
-    let mut chars = literal_text.chars();
-    unescape_char_or_byte(&mut chars, Mode::Char)
-        .map_err(|err| (literal_text.len() - chars.as_str().len(), err))
-}
-
-/// Takes a contents of a string literal (without quotes) and produces a
-/// sequence of escaped characters or errors.
-pub(crate) fn unescape_str<F>(literal_text: &str, callback: &mut F)
-where
-    F: FnMut(Range<usize>, Result<char, EscapeError>),
-{
-    unescape_str_or_byte_str(literal_text, Mode::Str, callback)
-}
-
-pub(crate) fn unescape_byte(literal_text: &str) -> Result<u8, (usize, EscapeError)> {
-    let mut chars = literal_text.chars();
-    unescape_char_or_byte(&mut chars, Mode::Byte)
-        .map(byte_from_char)
-        .map_err(|err| (literal_text.len() - chars.as_str().len(), err))
-}
-
-/// Takes a contents of a string literal (without quotes) and produces a
-/// sequence of escaped characters or errors.
-pub(crate) fn unescape_byte_str<F>(literal_text: &str, callback: &mut F)
-where
-    F: FnMut(Range<usize>, Result<u8, EscapeError>),
-{
-    unescape_str_or_byte_str(literal_text, Mode::ByteStr, &mut |range, char| {
-        callback(range, char.map(byte_from_char))
-    })
-}
-
-/// Takes a contents of a string literal (without quotes) and produces a
-/// sequence of characters or errors.
-/// NOTE: Raw strings do not perform any explicit character escaping, here we
-/// only translate CRLF to LF and produce errors on bare CR.
-pub(crate) fn unescape_raw_str<F>(literal_text: &str, callback: &mut F)
-where
-    F: FnMut(Range<usize>, Result<char, EscapeError>),
-{
-    unescape_raw_str_or_byte_str(literal_text, Mode::Str, callback)
-}
-
-/// Takes a contents of a string literal (without quotes) and produces a
-/// sequence of characters or errors.
-/// NOTE: Raw strings do not perform any explicit character escaping, here we
-/// only translate CRLF to LF and produce errors on bare CR.
-pub(crate) fn unescape_raw_byte_str<F>(literal_text: &str, callback: &mut F)
-where
-    F: FnMut(Range<usize>, Result<u8, EscapeError>),
-{
-    unescape_raw_str_or_byte_str(literal_text, Mode::ByteStr, &mut |range, char| {
-        callback(range, char.map(byte_from_char))
-    })
-}
-
-#[derive(Debug, Clone, Copy)]
-pub(crate) enum Mode {
-    Char,
-    Str,
-    Byte,
-    ByteStr,
-}
-
-impl Mode {
-    fn in_single_quotes(self) -> bool {
-        match self {
-            Mode::Char | Mode::Byte => true,
-            Mode::Str | Mode::ByteStr => false,
-        }
-    }
-
-    pub(crate) fn in_double_quotes(self) -> bool {
-        !self.in_single_quotes()
-    }
-
-    pub(crate) fn is_bytes(self) -> bool {
-        match self {
-            Mode::Byte | Mode::ByteStr => true,
-            Mode::Char | Mode::Str => false,
-        }
-    }
-}
-
-
-fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {
-    if first_char != '\\' {
-        return match first_char {
-            '\t' | '\n' => Err(EscapeError::EscapeOnlyChar),
-            '\r' => Err(if chars.clone().next() == Some('\n') {
-                EscapeError::EscapeOnlyChar
-            } else {
-                EscapeError::BareCarriageReturn
-            }),
-            '\'' if mode.in_single_quotes() => Err(EscapeError::EscapeOnlyChar),
-            '"' if mode.in_double_quotes() => Err(EscapeError::EscapeOnlyChar),
-            _ => {
-                if mode.is_bytes() && !first_char.is_ascii() {
-                    return Err(EscapeError::NonAsciiCharInByte);
-                }
-                Ok(first_char)
-            }
-        };
-    }
-
-    let second_char = chars.next().ok_or(EscapeError::LoneSlash)?;
-
-    let res = match second_char {
-        '"' => '"',
-        'n' => '\n',
-        'r' => '\r',
-        't' => '\t',
-        '\\' => '\\',
-        '\'' => '\'',
-        '0' => '\0',
-
-        'x' => {
-            let hi = chars.next().ok_or(EscapeError::TooShortHexEscape)?;
-            let hi = hi.to_digit(16).ok_or(EscapeError::InvalidCharInHexEscape)?;
-
-            let lo = chars.next().ok_or(EscapeError::TooShortHexEscape)?;
-            let lo = lo.to_digit(16).ok_or(EscapeError::InvalidCharInHexEscape)?;
-
-            let value = hi * 16 + lo;
-
-            if !mode.is_bytes() && !is_ascii(value) {
-                return Err(EscapeError::OutOfRangeHexEscape);
-            }
-            let value = value as u8;
-
-            value as char
-        }
-
-        'u' => {
-            if chars.next() != Some('{') {
-                return Err(EscapeError::NoBraceInUnicodeEscape);
-            }
-
-            let mut n_digits = 1;
-            let mut value: u32 = match chars.next().ok_or(EscapeError::UnclosedUnicodeEscape)? {
-                '_' => return Err(EscapeError::LeadingUnderscoreUnicodeEscape),
-                '}' => return Err(EscapeError::EmptyUnicodeEscape),
-                c => c.to_digit(16).ok_or(EscapeError::InvalidCharInUnicodeEscape)?,
-            };
-
-            loop {
-                match chars.next() {
-                    None => return Err(EscapeError::UnclosedUnicodeEscape),
-                    Some('_') => continue,
-                    Some('}') => {
-                        if n_digits > 6 {
-                            return Err(EscapeError::OverlongUnicodeEscape);
-                        }
-                        if mode.is_bytes() {
-                            return Err(EscapeError::UnicodeEscapeInByte);
-                        }
-
-                        break std::char::from_u32(value).ok_or_else(|| {
-                            if value > 0x10FFFF {
-                                EscapeError::OutOfRangeUnicodeEscape
-                            } else {
-                                EscapeError::LoneSurrogateUnicodeEscape
-                            }
-                        })?;
-                    }
-                    Some(c) => {
-                        let digit = c.to_digit(16).ok_or(EscapeError::InvalidCharInUnicodeEscape)?;
-                        n_digits += 1;
-                        if n_digits > 6 {
-                            continue;
-                        }
-                        let digit = digit as u32;
-                        value = value * 16 + digit;
-                    }
-                };
-            }
-        }
-        _ => return Err(EscapeError::InvalidEscape),
-    };
-    Ok(res)
-}
-
-fn unescape_char_or_byte(chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {
-    let first_char = chars.next().ok_or(EscapeError::ZeroChars)?;
-    let res = scan_escape(first_char, chars, mode)?;
-    if chars.next().is_some() {
-        return Err(EscapeError::MoreThanOneChar);
-    }
-    Ok(res)
-}
-
-/// Takes a contents of a string literal (without quotes) and produces a
-/// sequence of escaped characters or errors.
-fn unescape_str_or_byte_str<F>(src: &str, mode: Mode, callback: &mut F)
-where
-    F: FnMut(Range<usize>, Result<char, EscapeError>),
-{
-    assert!(mode.in_double_quotes());
-    let initial_len = src.len();
-    let mut chars = src.chars();
-    while let Some(first_char) = chars.next() {
-        let start = initial_len - chars.as_str().len() - first_char.len_utf8();
-
-        let unescaped_char = match first_char {
-            '\\' => {
-                let (second_char, third_char) = {
-                    let mut chars = chars.clone();
-                    (chars.next(), chars.next())
-                };
-                match (second_char, third_char) {
-                    (Some('\n'), _) | (Some('\r'), Some('\n')) => {
-                        skip_ascii_whitespace(&mut chars);
-                        continue;
-                    }
-                    _ => scan_escape(first_char, &mut chars, mode),
-                }
-            }
-            '\r' => {
-                let second_char = chars.clone().next();
-                if second_char == Some('\n') {
-                    chars.next();
-                    Ok('\n')
-                } else {
-                    scan_escape(first_char, &mut chars, mode)
-                }
-            }
-            '\n' => Ok('\n'),
-            '\t' => Ok('\t'),
-            _ => scan_escape(first_char, &mut chars, mode),
-        };
-        let end = initial_len - chars.as_str().len();
-        callback(start..end, unescaped_char);
-    }
-
-    fn skip_ascii_whitespace(chars: &mut Chars<'_>) {
-        let str = chars.as_str();
-        let first_non_space = str
-            .bytes()
-            .position(|b| b != b' ' && b != b'\t' && b != b'\n' && b != b'\r')
-            .unwrap_or(str.len());
-        *chars = str[first_non_space..].chars()
-    }
-}
-
-/// Takes a contents of a string literal (without quotes) and produces a
-/// sequence of characters or errors.
-/// NOTE: Raw strings do not perform any explicit character escaping, here we
-/// only translate CRLF to LF and produce errors on bare CR.
-fn unescape_raw_str_or_byte_str<F>(literal_text: &str, mode: Mode, callback: &mut F)
-where
-    F: FnMut(Range<usize>, Result<char, EscapeError>),
-{
-    assert!(mode.in_double_quotes());
-    let initial_len = literal_text.len();
-
-    let mut chars = literal_text.chars();
-    while let Some(curr) = chars.next() {
-        let start = initial_len - chars.as_str().len() - curr.len_utf8();
-
-        let result = match (curr, chars.clone().next()) {
-            ('\r', Some('\n')) => {
-                chars.next();
-                Ok('\n')
-            },
-            ('\r', _) => Err(EscapeError::BareCarriageReturnInRawString),
-            (c, _) if mode.is_bytes() && !c.is_ascii() =>
-                Err(EscapeError::NonAsciiCharInByteString),
-            (c, _) => Ok(c),
-        };
-        let end = initial_len - chars.as_str().len();
-
-        callback(start..end, result);
-    }
-}
-
-fn byte_from_char(c: char) -> u8 {
-    let res = c as u32;
-    assert!(res <= u8::max_value() as u32, "guaranteed because of Mode::Byte(Str)");
-    res as u8
-}
-
-fn is_ascii(x: u32) -> bool {
-    x <= 0x7F
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_unescape_char_bad() {
-        fn check(literal_text: &str, expected_error: EscapeError) {
-            let actual_result = unescape_char(literal_text).map_err(|(_offset, err)| err);
-            assert_eq!(actual_result, Err(expected_error));
-        }
-
-        check("", EscapeError::ZeroChars);
-        check(r"\", EscapeError::LoneSlash);
-
-        check("\n", EscapeError::EscapeOnlyChar);
-        check("\r\n", EscapeError::EscapeOnlyChar);
-        check("\t", EscapeError::EscapeOnlyChar);
-        check("'", EscapeError::EscapeOnlyChar);
-        check("\r", EscapeError::BareCarriageReturn);
-
-        check("spam", EscapeError::MoreThanOneChar);
-        check(r"\x0ff", EscapeError::MoreThanOneChar);
-        check(r#"\"a"#, EscapeError::MoreThanOneChar);
-        check(r"\na", EscapeError::MoreThanOneChar);
-        check(r"\ra", EscapeError::MoreThanOneChar);
-        check(r"\ta", EscapeError::MoreThanOneChar);
-        check(r"\\a", EscapeError::MoreThanOneChar);
-        check(r"\'a", EscapeError::MoreThanOneChar);
-        check(r"\0a", EscapeError::MoreThanOneChar);
-        check(r"\u{0}x", EscapeError::MoreThanOneChar);
-        check(r"\u{1F63b}}", EscapeError::MoreThanOneChar);
-
-        check(r"\v", EscapeError::InvalidEscape);
-        check(r"\💩", EscapeError::InvalidEscape);
-        check(r"\●", EscapeError::InvalidEscape);
-
-        check(r"\x", EscapeError::TooShortHexEscape);
-        check(r"\x0", EscapeError::TooShortHexEscape);
-        check(r"\xf", EscapeError::TooShortHexEscape);
-        check(r"\xa", EscapeError::TooShortHexEscape);
-        check(r"\xx", EscapeError::InvalidCharInHexEscape);
-        check(r"\xы", EscapeError::InvalidCharInHexEscape);
-        check(r"\x🦀", EscapeError::InvalidCharInHexEscape);
-        check(r"\xtt", EscapeError::InvalidCharInHexEscape);
-        check(r"\xff", EscapeError::OutOfRangeHexEscape);
-        check(r"\xFF", EscapeError::OutOfRangeHexEscape);
-        check(r"\x80", EscapeError::OutOfRangeHexEscape);
-
-        check(r"\u", EscapeError::NoBraceInUnicodeEscape);
-        check(r"\u[0123]", EscapeError::NoBraceInUnicodeEscape);
-        check(r"\u{0x}", EscapeError::InvalidCharInUnicodeEscape);
-        check(r"\u{", EscapeError::UnclosedUnicodeEscape);
-        check(r"\u{0000", EscapeError::UnclosedUnicodeEscape);
-        check(r"\u{}", EscapeError::EmptyUnicodeEscape);
-        check(r"\u{_0000}", EscapeError::LeadingUnderscoreUnicodeEscape);
-        check(r"\u{0000000}", EscapeError::OverlongUnicodeEscape);
-        check(r"\u{FFFFFF}", EscapeError::OutOfRangeUnicodeEscape);
-        check(r"\u{ffffff}", EscapeError::OutOfRangeUnicodeEscape);
-        check(r"\u{ffffff}", EscapeError::OutOfRangeUnicodeEscape);
-
-        check(r"\u{DC00}", EscapeError::LoneSurrogateUnicodeEscape);
-        check(r"\u{DDDD}", EscapeError::LoneSurrogateUnicodeEscape);
-        check(r"\u{DFFF}", EscapeError::LoneSurrogateUnicodeEscape);
-
-        check(r"\u{D800}", EscapeError::LoneSurrogateUnicodeEscape);
-        check(r"\u{DAAA}", EscapeError::LoneSurrogateUnicodeEscape);
-        check(r"\u{DBFF}", EscapeError::LoneSurrogateUnicodeEscape);
-    }
-
-    #[test]
-    fn test_unescape_char_good() {
-        fn check(literal_text: &str, expected_char: char) {
-            let actual_result = unescape_char(literal_text);
-            assert_eq!(actual_result, Ok(expected_char));
-        }
-
-        check("a", 'a');
-        check("ы", 'ы');
-        check("🦀", '🦀');
-
-        check(r#"\""#, '"');
-        check(r"\n", '\n');
-        check(r"\r", '\r');
-        check(r"\t", '\t');
-        check(r"\\", '\\');
-        check(r"\'", '\'');
-        check(r"\0", '\0');
-
-        check(r"\x00", '\0');
-        check(r"\x5a", 'Z');
-        check(r"\x5A", 'Z');
-        check(r"\x7f", 127 as char);
-
-        check(r"\u{0}", '\0');
-        check(r"\u{000000}", '\0');
-        check(r"\u{41}", 'A');
-        check(r"\u{0041}", 'A');
-        check(r"\u{00_41}", 'A');
-        check(r"\u{4__1__}", 'A');
-        check(r"\u{1F63b}", '😻');
-    }
-
-    #[test]
-    fn test_unescape_str_good() {
-        fn check(literal_text: &str, expected: &str) {
-            let mut buf = Ok(String::with_capacity(literal_text.len()));
-            unescape_str(literal_text, &mut |range, c| {
-                if let Ok(b) = &mut buf {
-                    match c {
-                        Ok(c) => b.push(c),
-                        Err(e) => buf = Err((range, e)),
-                    }
-                }
-            });
-            let buf = buf.as_ref().map(|it| it.as_ref());
-            assert_eq!(buf, Ok(expected))
-        }
-
-        check("foo", "foo");
-        check("", "");
-        check(" \t\n\r\n", " \t\n\n");
-
-        check("hello \\\n     world", "hello world");
-        check("hello \\\r\n     world", "hello world");
-        check("thread's", "thread's")
-    }
-
-    #[test]
-    fn test_unescape_byte_bad() {
-        fn check(literal_text: &str, expected_error: EscapeError) {
-            let actual_result = unescape_byte(literal_text).map_err(|(_offset, err)| err);
-            assert_eq!(actual_result, Err(expected_error));
-        }
-
-        check("", EscapeError::ZeroChars);
-        check(r"\", EscapeError::LoneSlash);
-
-        check("\n", EscapeError::EscapeOnlyChar);
-        check("\r\n", EscapeError::EscapeOnlyChar);
-        check("\t", EscapeError::EscapeOnlyChar);
-        check("'", EscapeError::EscapeOnlyChar);
-        check("\r", EscapeError::BareCarriageReturn);
-
-        check("spam", EscapeError::MoreThanOneChar);
-        check(r"\x0ff", EscapeError::MoreThanOneChar);
-        check(r#"\"a"#, EscapeError::MoreThanOneChar);
-        check(r"\na", EscapeError::MoreThanOneChar);
-        check(r"\ra", EscapeError::MoreThanOneChar);
-        check(r"\ta", EscapeError::MoreThanOneChar);
-        check(r"\\a", EscapeError::MoreThanOneChar);
-        check(r"\'a", EscapeError::MoreThanOneChar);
-        check(r"\0a", EscapeError::MoreThanOneChar);
-
-        check(r"\v", EscapeError::InvalidEscape);
-        check(r"\💩", EscapeError::InvalidEscape);
-        check(r"\●", EscapeError::InvalidEscape);
-
-        check(r"\x", EscapeError::TooShortHexEscape);
-        check(r"\x0", EscapeError::TooShortHexEscape);
-        check(r"\xa", EscapeError::TooShortHexEscape);
-        check(r"\xf", EscapeError::TooShortHexEscape);
-        check(r"\xx", EscapeError::InvalidCharInHexEscape);
-        check(r"\xы", EscapeError::InvalidCharInHexEscape);
-        check(r"\x🦀", EscapeError::InvalidCharInHexEscape);
-        check(r"\xtt", EscapeError::InvalidCharInHexEscape);
-
-        check(r"\u", EscapeError::NoBraceInUnicodeEscape);
-        check(r"\u[0123]", EscapeError::NoBraceInUnicodeEscape);
-        check(r"\u{0x}", EscapeError::InvalidCharInUnicodeEscape);
-        check(r"\u{", EscapeError::UnclosedUnicodeEscape);
-        check(r"\u{0000", EscapeError::UnclosedUnicodeEscape);
-        check(r"\u{}", EscapeError::EmptyUnicodeEscape);
-        check(r"\u{_0000}", EscapeError::LeadingUnderscoreUnicodeEscape);
-        check(r"\u{0000000}", EscapeError::OverlongUnicodeEscape);
-
-        check("ы", EscapeError::NonAsciiCharInByte);
-        check("🦀", EscapeError::NonAsciiCharInByte);
-
-        check(r"\u{0}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{000000}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{41}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{0041}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{00_41}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{4__1__}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{1F63b}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{0}x", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{1F63b}}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{FFFFFF}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{ffffff}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{ffffff}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DC00}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DDDD}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DFFF}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{D800}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DAAA}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DBFF}", EscapeError::UnicodeEscapeInByte);
-    }
-
-    #[test]
-    fn test_unescape_byte_good() {
-        fn check(literal_text: &str, expected_byte: u8) {
-            let actual_result = unescape_byte(literal_text);
-            assert_eq!(actual_result, Ok(expected_byte));
-        }
-
-        check("a", b'a');
-
-        check(r#"\""#, b'"');
-        check(r"\n", b'\n');
-        check(r"\r", b'\r');
-        check(r"\t", b'\t');
-        check(r"\\", b'\\');
-        check(r"\'", b'\'');
-        check(r"\0", b'\0');
-
-        check(r"\x00", b'\0');
-        check(r"\x5a", b'Z');
-        check(r"\x5A", b'Z');
-        check(r"\x7f", 127);
-        check(r"\x80", 128);
-        check(r"\xff", 255);
-        check(r"\xFF", 255);
-    }
-
-    #[test]
-    fn test_unescape_byte_str_good() {
-        fn check(literal_text: &str, expected: &[u8]) {
-            let mut buf = Ok(Vec::with_capacity(literal_text.len()));
-            unescape_byte_str(literal_text, &mut |range, c| {
-                if let Ok(b) = &mut buf {
-                    match c {
-                        Ok(c) => b.push(c),
-                        Err(e) => buf = Err((range, e)),
-                    }
-                }
-            });
-            let buf = buf.as_ref().map(|it| it.as_ref());
-            assert_eq!(buf, Ok(expected))
-        }
-
-        check("foo", b"foo");
-        check("", b"");
-        check(" \t\n\r\n", b" \t\n\n");
-
-        check("hello \\\n     world", b"hello world");
-        check("hello \\\r\n     world", b"hello world");
-        check("thread's", b"thread's")
-    }
-
-    #[test]
-    fn test_unescape_raw_str() {
-        fn check(literal: &str, expected: &[(Range<usize>, Result<char, EscapeError>)]) {
-            let mut unescaped = Vec::with_capacity(literal.len());
-            unescape_raw_str(literal, &mut |range, res| unescaped.push((range, res)));
-            assert_eq!(unescaped, expected);
-        }
-
-        check("\r\n", &[(0..2, Ok('\n'))]);
-        check("\r", &[(0..1, Err(EscapeError::BareCarriageReturnInRawString))]);
-        check("\rx", &[(0..1, Err(EscapeError::BareCarriageReturnInRawString)), (1..2, Ok('x'))]);
-    }
-
-    #[test]
-    fn test_unescape_raw_byte_str() {
-        fn check(literal: &str, expected: &[(Range<usize>, Result<u8, EscapeError>)]) {
-            let mut unescaped = Vec::with_capacity(literal.len());
-            unescape_raw_byte_str(literal, &mut |range, res| unescaped.push((range, res)));
-            assert_eq!(unescaped, expected);
-        }
-
-        check("\r\n", &[(0..2, Ok(byte_from_char('\n')))]);
-        check("\r", &[(0..1, Err(EscapeError::BareCarriageReturnInRawString))]);
-        check("🦀", &[(0..4, Err(EscapeError::NonAsciiCharInByteString))]);
-        check(
-            "🦀a",
-            &[(0..4, Err(EscapeError::NonAsciiCharInByteString)), (4..5, Ok(byte_from_char('a')))],
-        );
-    }
-}
diff --git a/src/libsyntax/parse/unescape_error_reporting.rs b/src/libsyntax/parse/unescape_error_reporting.rs
index 71b41161ad8..bc3ee8620e0 100644
--- a/src/libsyntax/parse/unescape_error_reporting.rs
+++ b/src/libsyntax/parse/unescape_error_reporting.rs
@@ -3,12 +3,11 @@
 use std::ops::Range;
 use std::iter::once;
 
+use rustc_lexer::unescape::{EscapeError, Mode};
 use syntax_pos::{Span, BytePos};
 
 use crate::errors::{Handler, Applicability};
 
-use super::unescape::{EscapeError, Mode};
-
 pub(crate) fn emit_unescape_error(
     handler: &Handler,
     // interior part of the literal, without quotes