Refactor cook_lexer_literal.

It deals with eight cases: ints, floats, and the six quoted types
(char/byte/strings). For ints and floats we have an early return, and
the other six types fall through to the code at the end, which makes the
function hard to read.

This commit rearranges things to avoid the early returns.

Author: nnethercote

compiler/rustc_parse/src/lexer/mod.rs

@@ -363,112 +363,103 @@ impl<'a> StringReader<'a> {
     fn cook_lexer_literal(
         &self,
         start: BytePos,
-        suffix_start: BytePos,
+        end: BytePos,
         kind: rustc_lexer::LiteralKind,
     ) -> (token::LitKind, Symbol) {
-        // prefix means `"` or `br"` or `r###"`, ...
-        let (lit_kind, mode, prefix_len, postfix_len) = match kind {
+        match kind {
             rustc_lexer::LiteralKind::Char { terminated } => {
                 if !terminated {
                     self.sess.span_diagnostic.span_fatal_with_code(
-                        self.mk_sp(start, suffix_start),
+                        self.mk_sp(start, end),
                         "unterminated character literal",
                         error_code!(E0762),
                     )
                 }
-                (token::Char, Mode::Char, 1, 1) // ' '
+                self.cook_quoted(token::Char, Mode::Char, start, end, 1, 1) // ' '
             }
             rustc_lexer::LiteralKind::Byte { terminated } => {
                 if !terminated {
                     self.sess.span_diagnostic.span_fatal_with_code(
-                        self.mk_sp(start + BytePos(1), suffix_start),
+                        self.mk_sp(start + BytePos(1), end),
                         "unterminated byte constant",
                         error_code!(E0763),
                     )
                 }
-                (token::Byte, Mode::Byte, 2, 1) // b' '
+                self.cook_quoted(token::Byte, Mode::Byte, start, end, 2, 1) // b' '
             }
             rustc_lexer::LiteralKind::Str { terminated } => {
                 if !terminated {
                     self.sess.span_diagnostic.span_fatal_with_code(
-                        self.mk_sp(start, suffix_start),
+                        self.mk_sp(start, end),
                         "unterminated double quote string",
                         error_code!(E0765),
                     )
                 }
-                (token::Str, Mode::Str, 1, 1) // " "
+                self.cook_quoted(token::Str, Mode::Str, start, end, 1, 1) // " "
             }
             rustc_lexer::LiteralKind::ByteStr { terminated } => {
                 if !terminated {
                     self.sess.span_diagnostic.span_fatal_with_code(
-                        self.mk_sp(start + BytePos(1), suffix_start),
+                        self.mk_sp(start + BytePos(1), end),
                         "unterminated double quote byte string",
                         error_code!(E0766),
                     )
                 }
-                (token::ByteStr, Mode::ByteStr, 2, 1) // b" "
+                self.cook_quoted(token::ByteStr, Mode::ByteStr, start, end, 2, 1) // b" "
             }
             rustc_lexer::LiteralKind::RawStr { n_hashes } => {
                 if let Some(n_hashes) = n_hashes {
                     let n = u32::from(n_hashes);
-                    (token::StrRaw(n_hashes), Mode::RawStr, 2 + n, 1 + n) // r##" "##
+                    let kind = token::StrRaw(n_hashes);
+                    self.cook_quoted(kind, Mode::RawStr, start, end, 2 + n, 1 + n) // r##" "##
                 } else {
                     self.report_raw_str_error(start, 1);
                 }
             }
             rustc_lexer::LiteralKind::RawByteStr { n_hashes } => {
                 if let Some(n_hashes) = n_hashes {
                     let n = u32::from(n_hashes);
-                    (token::ByteStrRaw(n_hashes), Mode::RawByteStr, 3 + n, 1 + n) // br##" "##
+                    let kind = token::ByteStrRaw(n_hashes);
+                    self.cook_quoted(kind, Mode::RawByteStr, start, end, 3 + n, 1 + n) // br##" "##
                 } else {
                     self.report_raw_str_error(start, 2);
                 }
             }
             rustc_lexer::LiteralKind::Int { base, empty_int } => {
-                return if empty_int {
+                if empty_int {
                     self.sess
                         .span_diagnostic
                         .struct_span_err_with_code(
-                            self.mk_sp(start, suffix_start),
+                            self.mk_sp(start, end),
                             "no valid digits found for number",
                             error_code!(E0768),
                         )
                         .emit();
                     (token::Integer, sym::integer(0))
                 } else {
-                    self.validate_int_literal(base, start, suffix_start);
-                    (token::Integer, self.symbol_from_to(start, suffix_start))
-                };
+                    self.validate_int_literal(base, start, end);
+                    (token::Integer, self.symbol_from_to(start, end))
+                }
             }
             rustc_lexer::LiteralKind::Float { base, empty_exponent } => {
                 if empty_exponent {
                     self.err_span_(start, self.pos, "expected at least one digit in exponent");
                 }
-
                 match base {
-                    Base::Hexadecimal => self.err_span_(
-                        start,
-                        suffix_start,
-                        "hexadecimal float literal is not supported",
-                    ),
+                    Base::Hexadecimal => {
+                        self.err_span_(start, end, "hexadecimal float literal is not supported")
+                    }
                     Base::Octal => {
-                        self.err_span_(start, suffix_start, "octal float literal is not supported")
+                        self.err_span_(start, end, "octal float literal is not supported")
                     }
                     Base::Binary => {
-                        self.err_span_(start, suffix_start, "binary float literal is not supported")
+                        self.err_span_(start, end, "binary float literal is not supported")
                     }
-                    _ => (),
+                    _ => {}
                 }
-
-                let id = self.symbol_from_to(start, suffix_start);
-                return (token::Float, id);
+                (token::Float, self.symbol_from_to(start, end))
             }
-        };
-        let content_start = start + BytePos(prefix_len);
-        let content_end = suffix_start - BytePos(postfix_len);
-        let id = self.symbol_from_to(content_start, content_end);
-        self.validate_literal_escape(mode, content_start, content_end, prefix_len, postfix_len);
-        (lit_kind, id)
+        }
     }
 
     #[inline]
@@ -659,20 +650,22 @@ impl<'a> StringReader<'a> {
         )
     }
 
-    fn validate_literal_escape(
+    fn cook_quoted(
         &self,
+        kind: token::LitKind,
         mode: Mode,
-        content_start: BytePos,
-        content_end: BytePos,
+        start: BytePos,
+        end: BytePos,
         prefix_len: u32,
         postfix_len: u32,
-    ) {
+    ) -> (token::LitKind, Symbol) {
+        let content_start = start + BytePos(prefix_len);
+        let content_end = end - BytePos(postfix_len);
         let lit_content = self.str_from_to(content_start, content_end);
         unescape::unescape_literal(lit_content, mode, &mut |range, result| {
             // Here we only check for errors. The actual unescaping is done later.
             if let Err(err) = result {
-                let span_with_quotes = self
-                    .mk_sp(content_start - BytePos(prefix_len), content_end + BytePos(postfix_len));
+                let span_with_quotes = self.mk_sp(start, end);
                 let (start, end) = (range.start as u32, range.end as u32);
                 let lo = content_start + BytePos(start);
                 let hi = lo + BytePos(end - start);
@@ -688,6 +681,7 @@ impl<'a> StringReader<'a> {
                 );
             }
         });
+        (kind, Symbol::intern(lit_content))
     }
 
     fn validate_int_literal(&self, base: Base, content_start: BytePos, content_end: BytePos) {