Merge #226

226: Validate byte literals and byte strings r=aochagavia a=aochagavia



Co-authored-by: Adolfo Ochagavía <[email protected]>

15 files changed, 1141 insertions, 507 deletions

diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index 2e9ae263a..bf056131e 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -372,6 +372,80 @@ impl<R: TreeRoot<RaTypes>> BreakExprNode<R> {
 
 impl<'a> BreakExpr<'a> {}
 
+// Byte
+#[derive(Debug, Clone, Copy,)]
+pub struct ByteNode<R: TreeRoot<RaTypes> = OwnedRoot> {
+    pub(crate) syntax: SyntaxNode<R>,
+}
+pub type Byte<'a> = ByteNode<RefRoot<'a>>;
+
+impl<R1: TreeRoot<RaTypes>, R2: TreeRoot<RaTypes>> PartialEq<ByteNode<R1>> for ByteNode<R2> {
+    fn eq(&self, other: &ByteNode<R1>) -> bool { self.syntax == other.syntax }
+}
+impl<R: TreeRoot<RaTypes>> Eq for ByteNode<R> {}
+impl<R: TreeRoot<RaTypes>> Hash for ByteNode<R> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.syntax.hash(state) }
+}
+
+impl<'a> AstNode<'a> for Byte<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            BYTE => Some(Byte { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<R: TreeRoot<RaTypes>> ByteNode<R> {
+    pub fn borrowed(&self) -> Byte {
+        ByteNode { syntax: self.syntax.borrowed() }
+    }
+    pub fn owned(&self) -> ByteNode {
+        ByteNode { syntax: self.syntax.owned() }
+    }
+}
+
+
+impl<'a> Byte<'a> {}
+
+// ByteString
+#[derive(Debug, Clone, Copy,)]
+pub struct ByteStringNode<R: TreeRoot<RaTypes> = OwnedRoot> {
+    pub(crate) syntax: SyntaxNode<R>,
+}
+pub type ByteString<'a> = ByteStringNode<RefRoot<'a>>;
+
+impl<R1: TreeRoot<RaTypes>, R2: TreeRoot<RaTypes>> PartialEq<ByteStringNode<R1>> for ByteStringNode<R2> {
+    fn eq(&self, other: &ByteStringNode<R1>) -> bool { self.syntax == other.syntax }
+}
+impl<R: TreeRoot<RaTypes>> Eq for ByteStringNode<R> {}
+impl<R: TreeRoot<RaTypes>> Hash for ByteStringNode<R> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.syntax.hash(state) }
+}
+
+impl<'a> AstNode<'a> for ByteString<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            BYTE_STRING => Some(ByteString { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<R: TreeRoot<RaTypes>> ByteStringNode<R> {
+    pub fn borrowed(&self) -> ByteString {
+        ByteStringNode { syntax: self.syntax.borrowed() }
+    }
+    pub fn owned(&self) -> ByteStringNode {
+        ByteStringNode { syntax: self.syntax.owned() }
+    }
+}
+
+
+impl<'a> ByteString<'a> {}
+
 // CallExpr
 #[derive(Debug, Clone, Copy,)]
 pub struct CallExprNode<R: TreeRoot<RaTypes> = OwnedRoot> {
diff --git a/crates/ra_syntax/src/ast/mod.rs b/crates/ra_syntax/src/ast/mod.rs
index f20714ede..7077e3492 100644
--- a/crates/ra_syntax/src/ast/mod.rs
+++ b/crates/ra_syntax/src/ast/mod.rs
@@ -134,6 +134,18 @@ impl<'a> Char<'a> {
     }
 }
 
+impl<'a> Byte<'a> {
+    pub fn text(&self) -> &SmolStr {
+        &self.syntax().leaf_text().unwrap()
+    }
+}
+
+impl<'a> ByteString<'a> {
+    pub fn text(&self) -> &SmolStr {
+        &self.syntax().leaf_text().unwrap()
+    }
+}
+
 impl<'a> String<'a> {
     pub fn text(&self) -> &SmolStr {
         &self.syntax().leaf_text().unwrap()
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index c3184667e..53cd2118f 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -412,6 +412,8 @@ Grammar(
         "RangeExpr": (),
         "BinExpr": (),
         "String": (),
+        "Byte": (),
+        "ByteString": (),
         "Char": (),
         "Literal": (),
 
diff --git a/crates/ra_syntax/src/string_lexing.rs b/crates/ra_syntax/src/string_lexing.rs
deleted file mode 100644
index d613bb042..000000000
--- a/crates/ra_syntax/src/string_lexing.rs
+++ /dev/null
@@ -1,414 +0,0 @@
-use self::CharComponentKind::*;
-use rowan::{TextRange, TextUnit};
-
-pub fn parse_string_literal(src: &str) -> StringComponentIterator {
-    StringComponentIterator {
-        parser: Parser::new(src),
-        has_closing_quote: false,
-    }
-}
-
-#[derive(Debug, Eq, PartialEq, Clone)]
-pub struct StringComponent {
-    pub range: TextRange,
-    pub kind: StringComponentKind,
-}
-
-impl StringComponent {
-    fn new(range: TextRange, kind: StringComponentKind) -> StringComponent {
-        StringComponent { range, kind }
-    }
-}
-
-#[derive(Debug, Eq, PartialEq, Clone)]
-pub enum StringComponentKind {
-    IgnoreNewline,
-    Char(CharComponentKind),
-}
-
-pub struct StringComponentIterator<'a> {
-    parser: Parser<'a>,
-    pub has_closing_quote: bool,
-}
-
-impl<'a> Iterator for StringComponentIterator<'a> {
-    type Item = StringComponent;
-    fn next(&mut self) -> Option<StringComponent> {
-        if self.parser.pos == 0 {
-            assert!(
-                self.parser.advance() == '"',
-                "string literal should start with double quotes"
-            );
-        }
-
-        if let Some(component) = self.parser.parse_string_component() {
-            return Some(component);
-        }
-
-        // We get here when there are no char components left to parse
-        if self.parser.peek() == Some('"') {
-            self.parser.advance();
-            self.has_closing_quote = true;
-        }
-
-        assert!(
-            self.parser.peek() == None,
-            "string literal should leave no unparsed input: src = {}, pos = {}, length = {}",
-            self.parser.src,
-            self.parser.pos,
-            self.parser.src.len()
-        );
-
-        None
-    }
-}
-
-pub fn parse_char_literal(src: &str) -> CharComponentIterator {
-    CharComponentIterator {
-        parser: Parser::new(src),
-        has_closing_quote: false,
-    }
-}
-
-#[derive(Debug, Eq, PartialEq, Clone)]
-pub struct CharComponent {
-    pub range: TextRange,
-    pub kind: CharComponentKind,
-}
-
-impl CharComponent {
-    fn new(range: TextRange, kind: CharComponentKind) -> CharComponent {
-        CharComponent { range, kind }
-    }
-}
-
-#[derive(Debug, Eq, PartialEq, Clone)]
-pub enum CharComponentKind {
-    CodePoint,
-    AsciiEscape,
-    AsciiCodeEscape,
-    UnicodeEscape,
-}
-
-pub struct CharComponentIterator<'a> {
-    parser: Parser<'a>,
-    pub has_closing_quote: bool,
-}
-
-impl<'a> Iterator for CharComponentIterator<'a> {
-    type Item = CharComponent;
-    fn next(&mut self) -> Option<CharComponent> {
-        if self.parser.pos == 0 {
-            assert!(
-                self.parser.advance() == '\'',
-                "char literal should start with a quote"
-            );
-        }
-
-        if let Some(component) = self.parser.parse_char_component() {
-            return Some(component);
-        }
-
-        // We get here when there are no char components left to parse
-        if self.parser.peek() == Some('\'') {
-            self.parser.advance();
-            self.has_closing_quote = true;
-        }
-
-        assert!(
-            self.parser.peek() == None,
-            "char literal should leave no unparsed input: src = {}, pos = {}, length = {}",
-            self.parser.src,
-            self.parser.pos,
-            self.parser.src.len()
-        );
-
-        None
-    }
-}
-
-pub struct Parser<'a> {
-    src: &'a str,
-    pos: usize,
-}
-
-impl<'a> Parser<'a> {
-    pub fn new(src: &'a str) -> Parser<'a> {
-        Parser { src, pos: 0 }
-    }
-
-    // Utility methods
-
-    pub fn peek(&self) -> Option<char> {
-        if self.pos == self.src.len() {
-            return None;
-        }
-
-        self.src[self.pos..].chars().next()
-    }
-
-    pub fn advance(&mut self) -> char {
-        let next = self
-            .peek()
-            .expect("cannot advance if end of input is reached");
-        self.pos += next.len_utf8();
-        next
-    }
-
-    pub fn skip_whitespace(&mut self) {
-        while self.peek().map(|c| c.is_whitespace()) == Some(true) {
-            self.advance();
-        }
-    }
-
-    pub fn get_pos(&self) -> TextUnit {
-        (self.pos as u32).into()
-    }
-
-    // Char parsing methods
-
-    fn parse_unicode_escape(&mut self, start: TextUnit) -> CharComponent {
-        match self.peek() {
-            Some('{') => {
-                self.advance();
-
-                // Parse anything until we reach `}`
-                while let Some(next) = self.peek() {
-                    self.advance();
-                    if next == '}' {
-                        break;
-                    }
-                }
-
-                let end = self.get_pos();
-                CharComponent::new(TextRange::from_to(start, end), UnicodeEscape)
-            }
-            Some(_) | None => {
-                let end = self.get_pos();
-                CharComponent::new(TextRange::from_to(start, end), UnicodeEscape)
-            }
-        }
-    }
-
-    fn parse_ascii_code_escape(&mut self, start: TextUnit) -> CharComponent {
-        let code_start = self.get_pos();
-        while let Some(next) = self.peek() {
-            if next == '\'' || (self.get_pos() - code_start == 2.into()) {
-                break;
-            }
-
-            self.advance();
-        }
-
-        let end = self.get_pos();
-        CharComponent::new(TextRange::from_to(start, end), AsciiCodeEscape)
-    }
-
-    fn parse_escape(&mut self, start: TextUnit) -> CharComponent {
-        if self.peek().is_none() {
-            return CharComponent::new(TextRange::from_to(start, start), AsciiEscape);
-        }
-
-        let next = self.advance();
-        let end = self.get_pos();
-        let range = TextRange::from_to(start, end);
-        match next {
-            'x' => self.parse_ascii_code_escape(start),
-            'u' => self.parse_unicode_escape(start),
-            _ => CharComponent::new(range, AsciiEscape),
-        }
-    }
-
-    pub fn parse_char_component(&mut self) -> Option<CharComponent> {
-        let next = self.peek()?;
-
-        // Ignore character close
-        if next == '\'' {
-            return None;
-        }
-
-        let start = self.get_pos();
-        self.advance();
-
-        if next == '\\' {
-            Some(self.parse_escape(start))
-        } else {
-            let end = self.get_pos();
-            Some(CharComponent::new(
-                TextRange::from_to(start, end),
-                CodePoint,
-            ))
-        }
-    }
-
-    pub fn parse_ignore_newline(&mut self, start: TextUnit) -> Option<StringComponent> {
-        // In string literals, when a `\` occurs immediately before the newline, the `\`,
-        // the newline, and all whitespace at the beginning of the next line are ignored
-        match self.peek() {
-            Some('\n') | Some('\r') => {
-                self.skip_whitespace();
-                Some(StringComponent::new(
-                    TextRange::from_to(start, self.get_pos()),
-                    StringComponentKind::IgnoreNewline,
-                ))
-            }
-            _ => None,
-        }
-    }
-
-    pub fn parse_string_component(&mut self) -> Option<StringComponent> {
-        let next = self.peek()?;
-
-        // Ignore string close
-        if next == '"' {
-            return None;
-        }
-
-        let start = self.get_pos();
-        self.advance();
-
-        if next == '\\' {
-            // Strings can use `\` to ignore newlines, so we first try to parse one of those
-            // before falling back to parsing char escapes
-            self.parse_ignore_newline(start).or_else(|| {
-                let char_component = self.parse_escape(start);
-                Some(StringComponent::new(
-                    char_component.range,
-                    StringComponentKind::Char(char_component.kind),
-                ))
-            })
-        } else {
-            let end = self.get_pos();
-            Some(StringComponent::new(
-                TextRange::from_to(start, end),
-                StringComponentKind::Char(CodePoint),
-            ))
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    fn parse(src: &str) -> (bool, Vec<CharComponent>) {
-        let component_iterator = &mut super::parse_char_literal(src);
-        let components: Vec<_> = component_iterator.collect();
-        (component_iterator.has_closing_quote, components)
-    }
-
-    fn unclosed_char_component(src: &str) -> CharComponent {
-        let (has_closing_quote, components) = parse(src);
-        assert!(!has_closing_quote, "char should not have closing quote");
-        assert!(components.len() == 1);
-        components[0].clone()
-    }
-
-    fn closed_char_component(src: &str) -> CharComponent {
-        let (has_closing_quote, components) = parse(src);
-        assert!(has_closing_quote, "char should have closing quote");
-        assert!(
-            components.len() == 1,
-            "Literal: {}\nComponents: {:#?}",
-            src,
-            components
-        );
-        components[0].clone()
-    }
-
-    fn closed_char_components(src: &str) -> Vec<CharComponent> {
-        let (has_closing_quote, components) = parse(src);
-        assert!(has_closing_quote, "char should have closing quote");
-        components
-    }
-
-    fn range_closed(src: &str) -> TextRange {
-        TextRange::from_to(1.into(), (src.len() as u32 - 1).into())
-    }
-
-    fn range_unclosed(src: &str) -> TextRange {
-        TextRange::from_to(1.into(), (src.len() as u32).into())
-    }
-
-    #[test]
-    fn test_unicode_escapes() {
-        let unicode_escapes = &[r"{DEAD}", "{BEEF}", "{FF}", "{}", ""];
-        for escape in unicode_escapes {
-            let escape_sequence = format!(r"'\u{}'", escape);
-            let component = closed_char_component(&escape_sequence);
-            let expected_range = range_closed(&escape_sequence);
-            assert_eq!(component.kind, CharComponentKind::UnicodeEscape);
-            assert_eq!(component.range, expected_range);
-        }
-    }
-
-    #[test]
-    fn test_unicode_escapes_unclosed() {
-        let unicode_escapes = &["{DEAD", "{BEEF", "{FF"];
-        for escape in unicode_escapes {
-            let escape_sequence = format!(r"'\u{}'", escape);
-            let component = unclosed_char_component(&escape_sequence);
-            let expected_range = range_unclosed(&escape_sequence);
-            assert_eq!(component.kind, CharComponentKind::UnicodeEscape);
-            assert_eq!(component.range, expected_range);
-        }
-    }
-
-    #[test]
-    fn test_empty_char() {
-        let (has_closing_quote, components) = parse("''");
-        assert!(has_closing_quote, "char should have closing quote");
-        assert!(components.len() == 0);
-    }
-
-    #[test]
-    fn test_unclosed_char() {
-        let component = unclosed_char_component("'a");
-        assert!(component.kind == CodePoint);
-        assert!(component.range == TextRange::from_to(1.into(), 2.into()));
-    }
-
-    #[test]
-    fn test_digit_escapes() {
-        let literals = &[r"", r"5", r"55"];
-
-        for literal in literals {
-            let lit_text = format!(r"'\x{}'", literal);
-            let component = closed_char_component(&lit_text);
-            assert!(component.kind == CharComponentKind::AsciiCodeEscape);
-            assert!(component.range == range_closed(&lit_text));
-        }
-
-        // More than 2 digits starts a new codepoint
-        let components = closed_char_components(r"'\x555'");
-        assert!(components.len() == 2);
-        assert!(components[1].kind == CharComponentKind::CodePoint);
-    }
-
-    #[test]
-    fn test_ascii_escapes() {
-        let literals = &[
-            r"\'", "\\\"", // equivalent to \"
-            r"\n", r"\r", r"\t", r"\\", r"\0",
-        ];
-
-        for literal in literals {
-            let lit_text = format!("'{}'", literal);
-            let component = closed_char_component(&lit_text);
-            assert!(component.kind == CharComponentKind::AsciiEscape);
-            assert!(component.range == range_closed(&lit_text));
-        }
-    }
-
-    #[test]
-    fn test_no_escapes() {
-        let literals = &['"', 'n', 'r', 't', '0', 'x', 'u'];
-
-        for &literal in literals {
-            let lit_text = format!("'{}'", literal);
-            let component = closed_char_component(&lit_text);
-            assert!(component.kind == CharComponentKind::CodePoint);
-            assert!(component.range == range_closed(&lit_text));
-        }
-    }
-}
diff --git a/crates/ra_syntax/src/string_lexing/byte.rs b/crates/ra_syntax/src/string_lexing/byte.rs
new file mode 100644
index 000000000..24424349c
--- /dev/null
+++ b/crates/ra_syntax/src/string_lexing/byte.rs
@@ -0,0 +1,51 @@
+use super::parser::Parser;
+use super::CharComponent;
+
+pub fn parse_byte_literal(src: &str) -> ByteComponentIterator {
+    ByteComponentIterator {
+        parser: Parser::new(src),
+        has_closing_quote: false,
+    }
+}
+
+pub struct ByteComponentIterator<'a> {
+    parser: Parser<'a>,
+    pub has_closing_quote: bool,
+}
+
+impl<'a> Iterator for ByteComponentIterator<'a> {
+    type Item = CharComponent;
+    fn next(&mut self) -> Option<CharComponent> {
+        if self.parser.pos == 0 {
+            assert!(
+                self.parser.advance() == 'b',
+                "Byte literal should start with a `b`"
+            );
+
+            assert!(
+                self.parser.advance() == '\'',
+                "Byte literal should start with a `b`, followed by a quote"
+            );
+        }
+
+        if let Some(component) = self.parser.parse_char_component() {
+            return Some(component);
+        }
+
+        // We get here when there are no char components left to parse
+        if self.parser.peek() == Some('\'') {
+            self.parser.advance();
+            self.has_closing_quote = true;
+        }
+
+        assert!(
+            self.parser.peek() == None,
+            "byte literal should leave no unparsed input: src = {}, pos = {}, length = {}",
+            self.parser.src,
+            self.parser.pos,
+            self.parser.src.len()
+        );
+
+        None
+    }
+}
diff --git a/crates/ra_syntax/src/string_lexing/byte_string.rs b/crates/ra_syntax/src/string_lexing/byte_string.rs
new file mode 100644
index 000000000..5b6dda760
--- /dev/null
+++ b/crates/ra_syntax/src/string_lexing/byte_string.rs
@@ -0,0 +1,51 @@
+use super::parser::Parser;
+use super::StringComponent;
+
+pub fn parse_byte_string_literal(src: &str) -> ByteStringComponentIterator {
+    ByteStringComponentIterator {
+        parser: Parser::new(src),
+        has_closing_quote: false,
+    }
+}
+
+pub struct ByteStringComponentIterator<'a> {
+    parser: Parser<'a>,
+    pub has_closing_quote: bool,
+}
+
+impl<'a> Iterator for ByteStringComponentIterator<'a> {
+    type Item = StringComponent;
+    fn next(&mut self) -> Option<StringComponent> {
+        if self.parser.pos == 0 {
+            assert!(
+                self.parser.advance() == 'b',
+                "byte string literal should start with a `b`"
+            );
+
+            assert!(
+                self.parser.advance() == '"',
+                "byte string literal should start with a `b`, followed by double quotes"
+            );
+        }
+
+        if let Some(component) = self.parser.parse_string_component() {
+            return Some(component);
+        }
+
+        // We get here when there are no char components left to parse
+        if self.parser.peek() == Some('"') {
+            self.parser.advance();
+            self.has_closing_quote = true;
+        }
+
+        assert!(
+            self.parser.peek() == None,
+            "byte string literal should leave no unparsed input: src = {}, pos = {}, length = {}",
+            self.parser.src,
+            self.parser.pos,
+            self.parser.src.len()
+        );
+
+        None
+    }
+}
diff --git a/crates/ra_syntax/src/string_lexing/char.rs b/crates/ra_syntax/src/string_lexing/char.rs
new file mode 100644
index 000000000..885c03b14
--- /dev/null
+++ b/crates/ra_syntax/src/string_lexing/char.rs
@@ -0,0 +1,176 @@
+use super::parser::Parser;
+use super::CharComponent;
+
+pub fn parse_char_literal(src: &str) -> CharComponentIterator {
+    CharComponentIterator {
+        parser: Parser::new(src),
+        has_closing_quote: false,
+    }
+}
+
+pub struct CharComponentIterator<'a> {
+    parser: Parser<'a>,
+    pub has_closing_quote: bool,
+}
+
+impl<'a> Iterator for CharComponentIterator<'a> {
+    type Item = CharComponent;
+    fn next(&mut self) -> Option<CharComponent> {
+        if self.parser.pos == 0 {
+            assert!(
+                self.parser.advance() == '\'',
+                "char literal should start with a quote"
+            );
+        }
+
+        if let Some(component) = self.parser.parse_char_component() {
+            return Some(component);
+        }
+
+        // We get here when there are no char components left to parse
+        if self.parser.peek() == Some('\'') {
+            self.parser.advance();
+            self.has_closing_quote = true;
+        }
+
+        assert!(
+            self.parser.peek() == None,
+            "char literal should leave no unparsed input: src = {}, pos = {}, length = {}",
+            self.parser.src,
+            self.parser.pos,
+            self.parser.src.len()
+        );
+
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use rowan::TextRange;
+    use crate::string_lexing::{
+        CharComponent,
+        CharComponentKind::*,
+};
+
+    fn parse(src: &str) -> (bool, Vec<CharComponent>) {
+        let component_iterator = &mut super::parse_char_literal(src);
+        let components: Vec<_> = component_iterator.collect();
+        (component_iterator.has_closing_quote, components)
+    }
+
+    fn unclosed_char_component(src: &str) -> CharComponent {
+        let (has_closing_quote, components) = parse(src);
+        assert!(!has_closing_quote, "char should not have closing quote");
+        assert!(components.len() == 1);
+        components[0].clone()
+    }
+
+    fn closed_char_component(src: &str) -> CharComponent {
+        let (has_closing_quote, components) = parse(src);
+        assert!(has_closing_quote, "char should have closing quote");
+        assert!(
+            components.len() == 1,
+            "Literal: {}\nComponents: {:#?}",
+            src,
+            components
+        );
+        components[0].clone()
+    }
+
+    fn closed_char_components(src: &str) -> Vec<CharComponent> {
+        let (has_closing_quote, components) = parse(src);
+        assert!(has_closing_quote, "char should have closing quote");
+        components
+    }
+
+    fn range_closed(src: &str) -> TextRange {
+        TextRange::from_to(1.into(), (src.len() as u32 - 1).into())
+    }
+
+    fn range_unclosed(src: &str) -> TextRange {
+        TextRange::from_to(1.into(), (src.len() as u32).into())
+    }
+
+    #[test]
+    fn test_unicode_escapes() {
+        let unicode_escapes = &[r"{DEAD}", "{BEEF}", "{FF}", "{}", ""];
+        for escape in unicode_escapes {
+            let escape_sequence = format!(r"'\u{}'", escape);
+            let component = closed_char_component(&escape_sequence);
+            let expected_range = range_closed(&escape_sequence);
+            assert_eq!(component.kind, UnicodeEscape);
+            assert_eq!(component.range, expected_range);
+        }
+    }
+
+    #[test]
+    fn test_unicode_escapes_unclosed() {
+        let unicode_escapes = &["{DEAD", "{BEEF", "{FF"];
+        for escape in unicode_escapes {
+            let escape_sequence = format!(r"'\u{}'", escape);
+            let component = unclosed_char_component(&escape_sequence);
+            let expected_range = range_unclosed(&escape_sequence);
+            assert_eq!(component.kind, UnicodeEscape);
+            assert_eq!(component.range, expected_range);
+        }
+    }
+
+    #[test]
+    fn test_empty_char() {
+        let (has_closing_quote, components) = parse("''");
+        assert!(has_closing_quote, "char should have closing quote");
+        assert!(components.len() == 0);
+    }
+
+    #[test]
+    fn test_unclosed_char() {
+        let component = unclosed_char_component("'a");
+        assert!(component.kind == CodePoint);
+        assert!(component.range == TextRange::from_to(1.into(), 2.into()));
+    }
+
+    #[test]
+    fn test_digit_escapes() {
+        let literals = &[r"", r"5", r"55"];
+
+        for literal in literals {
+            let lit_text = format!(r"'\x{}'", literal);
+            let component = closed_char_component(&lit_text);
+            assert!(component.kind == AsciiCodeEscape);
+            assert!(component.range == range_closed(&lit_text));
+        }
+
+        // More than 2 digits starts a new codepoint
+        let components = closed_char_components(r"'\x555'");
+        assert!(components.len() == 2);
+        assert!(components[1].kind == CodePoint);
+    }
+
+    #[test]
+    fn test_ascii_escapes() {
+        let literals = &[
+            r"\'", "\\\"", // equivalent to \"
+            r"\n", r"\r", r"\t", r"\\", r"\0",
+        ];
+
+        for literal in literals {
+            let lit_text = format!("'{}'", literal);
+            let component = closed_char_component(&lit_text);
+            assert!(component.kind == AsciiEscape);
+            assert!(component.range == range_closed(&lit_text));
+        }
+    }
+
+    #[test]
+    fn test_no_escapes() {
+        let literals = &['"', 'n', 'r', 't', '0', 'x', 'u'];
+
+        for &literal in literals {
+            let lit_text = format!("'{}'", literal);
+            let component = closed_char_component(&lit_text);
+            assert!(component.kind == CodePoint);
+            assert!(component.range == range_closed(&lit_text));
+        }
+    }
+}
diff --git a/crates/ra_syntax/src/string_lexing/mod.rs b/crates/ra_syntax/src/string_lexing/mod.rs
new file mode 100644
index 000000000..94853331f
--- /dev/null
+++ b/crates/ra_syntax/src/string_lexing/mod.rs
@@ -0,0 +1,13 @@
+mod parser;
+mod byte;
+mod byte_string;
+mod char;
+mod string;
+
+pub use self::{
+    byte::parse_byte_literal,
+    byte_string::parse_byte_string_literal,
+    char::parse_char_literal,
+    parser::{CharComponent, CharComponentKind, StringComponent, StringComponentKind},
+    string::parse_string_literal,
+};
diff --git a/crates/ra_syntax/src/string_lexing/parser.rs b/crates/ra_syntax/src/string_lexing/parser.rs
new file mode 100644
index 000000000..4a6d5bc93
--- /dev/null
+++ b/crates/ra_syntax/src/string_lexing/parser.rs
@@ -0,0 +1,201 @@
+use rowan::{TextRange, TextUnit};
+
+use self::CharComponentKind::*;
+
+pub struct Parser<'a> {
+    pub(super) src: &'a str,
+    pub(super) pos: usize,
+}
+
+impl<'a> Parser<'a> {
+    pub fn new(src: &'a str) -> Parser<'a> {
+        Parser { src, pos: 0 }
+    }
+
+    // Utility methods
+
+    pub fn peek(&self) -> Option<char> {
+        if self.pos == self.src.len() {
+            return None;
+        }
+
+        self.src[self.pos..].chars().next()
+    }
+
+    pub fn advance(&mut self) -> char {
+        let next = self
+            .peek()
+            .expect("cannot advance if end of input is reached");
+        self.pos += next.len_utf8();
+        next
+    }
+
+    pub fn skip_whitespace(&mut self) {
+        while self.peek().map(|c| c.is_whitespace()) == Some(true) {
+            self.advance();
+        }
+    }
+
+    pub fn get_pos(&self) -> TextUnit {
+        (self.pos as u32).into()
+    }
+
+    // Char parsing methods
+
+    fn parse_unicode_escape(&mut self, start: TextUnit) -> CharComponent {
+        match self.peek() {
+            Some('{') => {
+                self.advance();
+
+                // Parse anything until we reach `}`
+                while let Some(next) = self.peek() {
+                    self.advance();
+                    if next == '}' {
+                        break;
+                    }
+                }
+
+                let end = self.get_pos();
+                CharComponent::new(TextRange::from_to(start, end), UnicodeEscape)
+            }
+            Some(_) | None => {
+                let end = self.get_pos();
+                CharComponent::new(TextRange::from_to(start, end), UnicodeEscape)
+            }
+        }
+    }
+
+    fn parse_ascii_code_escape(&mut self, start: TextUnit) -> CharComponent {
+        let code_start = self.get_pos();
+        while let Some(next) = self.peek() {
+            if next == '\'' || (self.get_pos() - code_start == 2.into()) {
+                break;
+            }
+
+            self.advance();
+        }
+
+        let end = self.get_pos();
+        CharComponent::new(TextRange::from_to(start, end), AsciiCodeEscape)
+    }
+
+    fn parse_escape(&mut self, start: TextUnit) -> CharComponent {
+        if self.peek().is_none() {
+            return CharComponent::new(TextRange::from_to(start, start), AsciiEscape);
+        }
+
+        let next = self.advance();
+        let end = self.get_pos();
+        let range = TextRange::from_to(start, end);
+        match next {
+            'x' => self.parse_ascii_code_escape(start),
+            'u' => self.parse_unicode_escape(start),
+            _ => CharComponent::new(range, AsciiEscape),
+        }
+    }
+
+    pub fn parse_char_component(&mut self) -> Option<CharComponent> {
+        let next = self.peek()?;
+
+        // Ignore character close
+        if next == '\'' {
+            return None;
+        }
+
+        let start = self.get_pos();
+        self.advance();
+
+        if next == '\\' {
+            Some(self.parse_escape(start))
+        } else {
+            let end = self.get_pos();
+            Some(CharComponent::new(
+                TextRange::from_to(start, end),
+                CodePoint,
+            ))
+        }
+    }
+
+    pub fn parse_ignore_newline(&mut self, start: TextUnit) -> Option<StringComponent> {
+        // In string literals, when a `\` occurs immediately before the newline, the `\`,
+        // the newline, and all whitespace at the beginning of the next line are ignored
+        match self.peek() {
+            Some('\n') | Some('\r') => {
+                self.skip_whitespace();
+                Some(StringComponent::new(
+                    TextRange::from_to(start, self.get_pos()),
+                    StringComponentKind::IgnoreNewline,
+                ))
+            }
+            _ => None,
+        }
+    }
+
+    pub fn parse_string_component(&mut self) -> Option<StringComponent> {
+        let next = self.peek()?;
+
+        // Ignore string close
+        if next == '"' {
+            return None;
+        }
+
+        let start = self.get_pos();
+        self.advance();
+
+        if next == '\\' {
+            // Strings can use `\` to ignore newlines, so we first try to parse one of those
+            // before falling back to parsing char escapes
+            self.parse_ignore_newline(start).or_else(|| {
+                let char_component = self.parse_escape(start);
+                Some(StringComponent::new(
+                    char_component.range,
+                    StringComponentKind::Char(char_component.kind),
+                ))
+            })
+        } else {
+            let end = self.get_pos();
+            Some(StringComponent::new(
+                TextRange::from_to(start, end),
+                StringComponentKind::Char(CodePoint),
+            ))
+        }
+    }
+}
+
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub struct StringComponent {
+    pub range: TextRange,
+    pub kind: StringComponentKind,
+}
+
+impl StringComponent {
+    fn new(range: TextRange, kind: StringComponentKind) -> StringComponent {
+        StringComponent { range, kind }
+    }
+}
+
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub enum StringComponentKind {
+    IgnoreNewline,
+    Char(CharComponentKind),
+}
+
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub struct CharComponent {
+    pub range: TextRange,
+    pub kind: CharComponentKind,
+}
+
+impl CharComponent {
+    fn new(range: TextRange, kind: CharComponentKind) -> CharComponent {
+        CharComponent { range, kind }
+    }
+}
+
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub enum CharComponentKind {
+    CodePoint,
+    AsciiEscape,
+    AsciiCodeEscape,
+    UnicodeEscape,
+}
diff --git a/crates/ra_syntax/src/string_lexing/string.rs b/crates/ra_syntax/src/string_lexing/string.rs
new file mode 100644
index 000000000..1b23029c6
--- /dev/null
+++ b/crates/ra_syntax/src/string_lexing/string.rs
@@ -0,0 +1,46 @@
+use super::parser::Parser;
+use super::StringComponent;
+
+pub fn parse_string_literal(src: &str) -> StringComponentIterator {
+    StringComponentIterator {
+        parser: Parser::new(src),
+        has_closing_quote: false,
+    }
+}
+
+pub struct StringComponentIterator<'a> {
+    parser: Parser<'a>,
+    pub has_closing_quote: bool,
+}
+
+impl<'a> Iterator for StringComponentIterator<'a> {
+    type Item = StringComponent;
+    fn next(&mut self) -> Option<StringComponent> {
+        if self.parser.pos == 0 {
+            assert!(
+                self.parser.advance() == '"',
+                "string literal should start with double quotes"
+            );
+        }
+
+        if let Some(component) = self.parser.parse_string_component() {
+            return Some(component);
+        }
+
+        // We get here when there are no char components left to parse
+        if self.parser.peek() == Some('"') {
+            self.parser.advance();
+            self.has_closing_quote = true;
+        }
+
+        assert!(
+            self.parser.peek() == None,
+            "string literal should leave no unparsed input: src = {}, pos = {}, length = {}",
+            self.parser.src,
+            self.parser.pos,
+            self.parser.src.len()
+        );
+
+        None
+    }
+}
diff --git a/crates/ra_syntax/src/validation/byte.rs b/crates/ra_syntax/src/validation/byte.rs
new file mode 100644
index 000000000..43c0d7edd
--- /dev/null
+++ b/crates/ra_syntax/src/validation/byte.rs
@@ -0,0 +1,211 @@
+//! Validation of byte literals
+
+use crate::{
+    ast::{self, AstNode},
+    string_lexing::{self, CharComponentKind},
+    TextRange,
+    validation::char,
+    yellow::{
+        SyntaxError,
+        SyntaxErrorKind::*,
+    },
+};
+
+pub(super) fn validate_byte_node(node: ast::Byte, errors: &mut Vec<SyntaxError>) {
+    let literal_text = node.text();
+    let literal_range = node.syntax().range();
+    let mut components = string_lexing::parse_byte_literal(literal_text);
+    let mut len = 0;
+    for component in &mut components {
+        len += 1;
+        let text = &literal_text[component.range];
+        let range = component.range + literal_range.start();
+        validate_byte_component(text, component.kind, range, errors);
+    }
+
+    if !components.has_closing_quote {
+        errors.push(SyntaxError::new(UnclosedByte, literal_range));
+    }
+
+    if len == 0 {
+        errors.push(SyntaxError::new(EmptyByte, literal_range));
+    }
+
+    if len > 1 {
+        errors.push(SyntaxError::new(OverlongByte, literal_range));
+    }
+}
+
+pub(super) fn validate_byte_component(
+    text: &str,
+    kind: CharComponentKind,
+    range: TextRange,
+    errors: &mut Vec<SyntaxError>,
+) {
+    use self::CharComponentKind::*;
+    match kind {
+        AsciiEscape => validate_byte_escape(text, range, errors),
+        AsciiCodeEscape => validate_byte_code_escape(text, range, errors),
+        UnicodeEscape => errors.push(SyntaxError::new(UnicodeEscapeForbidden, range)),
+        CodePoint => {
+            let c = text
+                .chars()
+                .next()
+                .expect("Code points should be one character long");
+
+            // These bytes must always be escaped
+            if c == '\t' || c == '\r' || c == '\n' {
+                errors.push(SyntaxError::new(UnescapedByte, range));
+            }
+
+            // Only ASCII bytes are allowed
+            if c > 0x7F as char {
+                errors.push(SyntaxError::new(ByteOutOfRange, range));
+            }
+        }
+    }
+}
+
+fn validate_byte_escape(text: &str, range: TextRange, errors: &mut Vec<SyntaxError>) {
+    if text.len() == 1 {
+        // Escape sequence consists only of leading `\`
+        errors.push(SyntaxError::new(EmptyByteEscape, range));
+    } else {
+        let escape_code = text.chars().skip(1).next().unwrap();
+        if !char::is_ascii_escape(escape_code) {
+            errors.push(SyntaxError::new(InvalidByteEscape, range));
+        }
+    }
+}
+
+fn validate_byte_code_escape(text: &str, range: TextRange, errors: &mut Vec<SyntaxError>) {
+    // A ByteCodeEscape has 4 chars, example: `\xDD`
+    if text.len() < 4 {
+        errors.push(SyntaxError::new(TooShortByteCodeEscape, range));
+    } else {
+        assert!(
+            text.chars().count() == 4,
+            "ByteCodeEscape cannot be longer than 4 chars"
+        );
+
+        if u8::from_str_radix(&text[2..], 16).is_err() {
+            errors.push(SyntaxError::new(MalformedByteCodeEscape, range));
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::SourceFileNode;
+
+    fn build_file(literal: &str) -> SourceFileNode {
+        let src = format!("const C: u8 = b'{}';", literal);
+        SourceFileNode::parse(&src)
+    }
+
+    fn assert_valid_byte(literal: &str) {
+        let file = build_file(literal);
+        assert!(
+            file.errors().len() == 0,
+            "Errors for literal '{}': {:?}",
+            literal,
+            file.errors()
+        );
+    }
+
+    fn assert_invalid_byte(literal: &str) {
+        let file = build_file(literal);
+        assert!(file.errors().len() > 0);
+    }
+
+    #[test]
+    fn test_ansi_codepoints() {
+        for byte in 0..128 {
+            match byte {
+                b'\n' | b'\r' | b'\t' => assert_invalid_byte(&(byte as char).to_string()),
+                b'\'' | b'\\' => { /* Ignore character close and backslash */ }
+                _ => assert_valid_byte(&(byte as char).to_string()),
+            }
+        }
+
+        for byte in 128..=255u8 {
+            assert_invalid_byte(&(byte as char).to_string());
+        }
+    }
+
+    #[test]
+    fn test_unicode_codepoints() {
+        let invalid = ["Ƒ", "バ", "メ", "﷽"];
+        for c in &invalid {
+            assert_invalid_byte(c);
+        }
+    }
+
+    #[test]
+    fn test_unicode_multiple_codepoints() {
+        let invalid = ["नी", "👨‍👨‍"];
+        for c in &invalid {
+            assert_invalid_byte(c);
+        }
+    }
+
+    #[test]
+    fn test_valid_byte_escape() {
+        let valid = [r"\'", "\"", "\\\\", "\\\"", r"\n", r"\r", r"\t", r"\0"];
+        for c in &valid {
+            assert_valid_byte(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_byte_escape() {
+        let invalid = [r"\a", r"\?", r"\"];
+        for c in &invalid {
+            assert_invalid_byte(c);
+        }
+    }
+
+    #[test]
+    fn test_valid_byte_code_escape() {
+        let valid = [r"\x00", r"\x7F", r"\x55", r"\xF0"];
+        for c in &valid {
+            assert_valid_byte(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_byte_code_escape() {
+        let invalid = [r"\x", r"\x7"];
+        for c in &invalid {
+            assert_invalid_byte(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_unicode_escape() {
+        let well_formed = [
+            r"\u{FF}",
+            r"\u{0}",
+            r"\u{F}",
+            r"\u{10FFFF}",
+            r"\u{1_0__FF___FF_____}",
+        ];
+        for c in &well_formed {
+            assert_invalid_byte(c);
+        }
+
+        let invalid = [
+            r"\u",
+            r"\u{}",
+            r"\u{",
+            r"\u{FF",
+            r"\u{FFFFFF}",
+            r"\u{_F}",
+            r"\u{00FFFFF}",
+            r"\u{110000}",
+        ];
+        for c in &invalid {
+            assert_invalid_byte(c);
+        }
+    }
+}
diff --git a/crates/ra_syntax/src/validation/byte_string.rs b/crates/ra_syntax/src/validation/byte_string.rs
new file mode 100644
index 000000000..7b830e97c
--- /dev/null
+++ b/crates/ra_syntax/src/validation/byte_string.rs
@@ -0,0 +1,178 @@
+use crate::{
+    ast::{self, AstNode},
+    string_lexing::{self, StringComponentKind},
+    yellow::{
+        SyntaxError,
+        SyntaxErrorKind::*,
+    },
+};
+
+use super::byte;
+
+pub(crate) fn validate_byte_string_node(node: ast::ByteString, errors: &mut Vec<SyntaxError>) {
+    let literal_text = node.text();
+    let literal_range = node.syntax().range();
+    let mut components = string_lexing::parse_byte_string_literal(literal_text);
+    for component in &mut components {
+        let range = component.range + literal_range.start();
+
+        match component.kind {
+            StringComponentKind::Char(kind) => {
+                // Chars must escape \t, \n and \r codepoints, but strings don't
+                let text = &literal_text[component.range];
+                match text {
+                    "\t" | "\n" | "\r" => { /* always valid */ }
+                    _ => byte::validate_byte_component(text, kind, range, errors),
+                }
+            }
+            StringComponentKind::IgnoreNewline => { /* always valid */ }
+        }
+    }
+
+    if !components.has_closing_quote {
+        errors.push(SyntaxError::new(UnclosedString, literal_range));
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::SourceFileNode;
+
+    fn build_file(literal: &str) -> SourceFileNode {
+        let src = format!(r#"const S: &'static [u8] = b"{}";"#, literal);
+        println!("Source: {}", src);
+        SourceFileNode::parse(&src)
+    }
+
+    fn assert_valid_str(literal: &str) {
+        let file = build_file(literal);
+        assert!(
+            file.errors().len() == 0,
+            "Errors for literal '{}': {:?}",
+            literal,
+            file.errors()
+        );
+    }
+
+    fn assert_invalid_str(literal: &str) {
+        let file = build_file(literal);
+        assert!(file.errors().len() > 0);
+    }
+
+    #[test]
+    fn test_ansi_codepoints() {
+        for byte in 0..128 {
+            match byte {
+                b'\"' | b'\\' => { /* Ignore string close and backslash */ }
+                _ => assert_valid_str(&(byte as char).to_string()),
+            }
+        }
+
+        for byte in 128..=255u8 {
+            assert_invalid_str(&(byte as char).to_string());
+        }
+    }
+
+    #[test]
+    fn test_unicode_codepoints() {
+        let invalid = ["Ƒ", "バ", "メ", "﷽"];
+        for c in &invalid {
+            assert_invalid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_unicode_multiple_codepoints() {
+        let invalid = ["नी", "👨‍👨‍"];
+        for c in &invalid {
+            assert_invalid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_valid_ascii_escape() {
+        let valid = [r"\'", r#"\""#, r"\\", r"\n", r"\r", r"\t", r"\0", "a", "b"];
+        for c in &valid {
+            assert_valid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_ascii_escape() {
+        let invalid = [r"\a", r"\?", r"\"];
+        for c in &invalid {
+            assert_invalid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_valid_ascii_code_escape() {
+        let valid = [r"\x00", r"\x7F", r"\x55", r"\xF0"];
+        for c in &valid {
+            assert_valid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_ascii_code_escape() {
+        let invalid = [r"\x", r"\x7"];
+        for c in &invalid {
+            assert_invalid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_unicode_escape() {
+        let well_formed = [
+            r"\u{FF}",
+            r"\u{0}",
+            r"\u{F}",
+            r"\u{10FFFF}",
+            r"\u{1_0__FF___FF_____}",
+        ];
+        for c in &well_formed {
+            assert_invalid_str(c);
+        }
+
+        let invalid = [
+            r"\u",
+            r"\u{}",
+            r"\u{",
+            r"\u{FF",
+            r"\u{FFFFFF}",
+            r"\u{_F}",
+            r"\u{00FFFFF}",
+            r"\u{110000}",
+        ];
+        for c in &invalid {
+            assert_invalid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_mixed_invalid() {
+        assert_invalid_str(
+            r"This is the tale of a string
+with a newline in between, some emoji (👨‍👨‍) here and there,
+unicode escapes like this: \u{1FFBB} and weird stuff like
+this ﷽",
+        );
+    }
+
+    #[test]
+    fn test_mixed_valid() {
+        assert_valid_str(
+            r"This is the tale of a string
+with a newline in between, no emoji at all,
+nor unicode escapes or weird stuff",
+        );
+    }
+
+    #[test]
+    fn test_ignore_newline() {
+        assert_valid_str(
+            "Hello \
+             World",
+        );
+    }
+}
diff --git a/crates/ra_syntax/src/validation/char.rs b/crates/ra_syntax/src/validation/char.rs
index 63f9bad24..4728c85e6 100644
--- a/crates/ra_syntax/src/validation/char.rs
+++ b/crates/ra_syntax/src/validation/char.rs
@@ -1,3 +1,5 @@
+//! Validation of char literals
+
 use std::u32;
 
 use arrayvec::ArrayString;
@@ -12,7 +14,7 @@ use crate::{
     },
 };
 
-pub(crate) fn validate_char_node(node: ast::Char, errors: &mut Vec<SyntaxError>) {
+pub(super) fn validate_char_node(node: ast::Char, errors: &mut Vec<SyntaxError>) {
     let literal_text = node.text();
     let literal_range = node.syntax().range();
     let mut components = string_lexing::parse_char_literal(literal_text);
@@ -37,7 +39,7 @@ pub(crate) fn validate_char_node(node: ast::Char, errors: &mut Vec<SyntaxError>)
     }
 }
 
-pub(crate) fn validate_char_component(
+pub(super) fn validate_char_component(
     text: &str,
     kind: CharComponentKind,
     range: TextRange,
@@ -46,109 +48,115 @@ pub(crate) fn validate_char_component(
     // Validate escapes
     use self::CharComponentKind::*;
     match kind {
-        AsciiEscape => {
-            if text.len() == 1 {
-                // Escape sequence consists only of leading `\`
-                errors.push(SyntaxError::new(EmptyAsciiEscape, range));
-            } else {
-                let escape_code = text.chars().skip(1).next().unwrap();
-                if !is_ascii_escape(escape_code) {
-                    errors.push(SyntaxError::new(InvalidAsciiEscape, range));
-                }
+        AsciiEscape => validate_ascii_escape(text, range, errors),
+        AsciiCodeEscape => validate_ascii_code_escape(text, range, errors),
+        UnicodeEscape => validate_unicode_escape(text, range, errors),
+        CodePoint => {
+            // These code points must always be escaped
+            if text == "\t" || text == "\r" || text == "\n" {
+                errors.push(SyntaxError::new(UnescapedCodepoint, range));
             }
         }
-        AsciiCodeEscape => {
-            // An AsciiCodeEscape has 4 chars, example: `\xDD`
-            if text.len() < 4 {
-                errors.push(SyntaxError::new(TooShortAsciiCodeEscape, range));
-            } else {
-                assert!(
-                    text.chars().count() == 4,
-                    "AsciiCodeEscape cannot be longer than 4 chars"
-                );
-
-                match u8::from_str_radix(&text[2..], 16) {
-                    Ok(code) if code < 128 => { /* Escape code is valid */ }
-                    Ok(_) => errors.push(SyntaxError::new(AsciiCodeEscapeOutOfRange, range)),
-                    Err(_) => errors.push(SyntaxError::new(MalformedAsciiCodeEscape, range)),
-                }
-            }
+    }
+}
+
+fn validate_ascii_escape(text: &str, range: TextRange, errors: &mut Vec<SyntaxError>) {
+    if text.len() == 1 {
+        // Escape sequence consists only of leading `\`
+        errors.push(SyntaxError::new(EmptyAsciiEscape, range));
+    } else {
+        let escape_code = text.chars().skip(1).next().unwrap();
+        if !is_ascii_escape(escape_code) {
+            errors.push(SyntaxError::new(InvalidAsciiEscape, range));
         }
-        UnicodeEscape => {
-            assert!(&text[..2] == "\\u", "UnicodeEscape always starts with \\u");
+    }
+}
 
-            if text.len() == 2 {
-                // No starting `{`
-                errors.push(SyntaxError::new(MalformedUnicodeEscape, range));
-                return;
-            }
+pub(super) fn is_ascii_escape(code: char) -> bool {
+    match code {
+        '\\' | '\'' | '"' | 'n' | 'r' | 't' | '0' => true,
+        _ => false,
+    }
+}
 
-            if text.len() == 3 {
-                // Only starting `{`
-                errors.push(SyntaxError::new(UnclosedUnicodeEscape, range));
-                return;
-            }
+fn validate_ascii_code_escape(text: &str, range: TextRange, errors: &mut Vec<SyntaxError>) {
+    // An AsciiCodeEscape has 4 chars, example: `\xDD`
+    if text.len() < 4 {
+        errors.push(SyntaxError::new(TooShortAsciiCodeEscape, range));
+    } else {
+        assert!(
+            text.chars().count() == 4,
+            "AsciiCodeEscape cannot be longer than 4 chars"
+        );
 
-            let mut code = ArrayString::<[_; 6]>::new();
-            let mut closed = false;
-            for c in text[3..].chars() {
-                assert!(!closed, "no characters after escape is closed");
-
-                if c.is_digit(16) {
-                    if code.len() == 6 {
-                        errors.push(SyntaxError::new(OverlongUnicodeEscape, range));
-                        return;
-                    }
-
-                    code.push(c);
-                } else if c == '_' {
-                    // Reject leading _
-                    if code.len() == 0 {
-                        errors.push(SyntaxError::new(MalformedUnicodeEscape, range));
-                        return;
-                    }
-                } else if c == '}' {
-                    closed = true;
-                } else {
-                    errors.push(SyntaxError::new(MalformedUnicodeEscape, range));
-                    return;
-                }
-            }
+        match u8::from_str_radix(&text[2..], 16) {
+            Ok(code) if code < 128 => { /* Escape code is valid */ }
+            Ok(_) => errors.push(SyntaxError::new(AsciiCodeEscapeOutOfRange, range)),
+            Err(_) => errors.push(SyntaxError::new(MalformedAsciiCodeEscape, range)),
+        }
+    }
+}
 
-            if !closed {
-                errors.push(SyntaxError::new(UnclosedUnicodeEscape, range))
-            }
+fn validate_unicode_escape(text: &str, range: TextRange, errors: &mut Vec<SyntaxError>) {
+    assert!(&text[..2] == "\\u", "UnicodeEscape always starts with \\u");
 
-            if code.len() == 0 {
-                errors.push(SyntaxError::new(EmptyUnicodeEcape, range));
+    if text.len() == 2 {
+        // No starting `{`
+        errors.push(SyntaxError::new(MalformedUnicodeEscape, range));
+        return;
+    }
+
+    if text.len() == 3 {
+        // Only starting `{`
+        errors.push(SyntaxError::new(UnclosedUnicodeEscape, range));
+        return;
+    }
+
+    let mut code = ArrayString::<[_; 6]>::new();
+    let mut closed = false;
+    for c in text[3..].chars() {
+        assert!(!closed, "no characters after escape is closed");
+
+        if c.is_digit(16) {
+            if code.len() == 6 {
+                errors.push(SyntaxError::new(OverlongUnicodeEscape, range));
                 return;
             }
 
-            match u32::from_str_radix(&code, 16) {
-                Ok(code_u32) if code_u32 > 0x10FFFF => {
-                    errors.push(SyntaxError::new(UnicodeEscapeOutOfRange, range));
-                }
-                Ok(_) => {
-                    // Valid escape code
-                }
-                Err(_) => {
-                    errors.push(SyntaxError::new(MalformedUnicodeEscape, range));
-                }
-            }
-        }
-        CodePoint => {
-            // These code points must always be escaped
-            if text == "\t" || text == "\r" {
-                errors.push(SyntaxError::new(UnescapedCodepoint, range));
+            code.push(c);
+        } else if c == '_' {
+            // Reject leading _
+            if code.len() == 0 {
+                errors.push(SyntaxError::new(MalformedUnicodeEscape, range));
+                return;
             }
+        } else if c == '}' {
+            closed = true;
+        } else {
+            errors.push(SyntaxError::new(MalformedUnicodeEscape, range));
+            return;
         }
     }
-}
 
-fn is_ascii_escape(code: char) -> bool {
-    match code {
-        '\\' | '\'' | '"' | 'n' | 'r' | 't' | '0' => true,
-        _ => false,
+    if !closed {
+        errors.push(SyntaxError::new(UnclosedUnicodeEscape, range))
+    }
+
+    if code.len() == 0 {
+        errors.push(SyntaxError::new(EmptyUnicodeEcape, range));
+        return;
+    }
+
+    match u32::from_str_radix(&code, 16) {
+        Ok(code_u32) if code_u32 > 0x10FFFF => {
+            errors.push(SyntaxError::new(UnicodeEscapeOutOfRange, range));
+        }
+        Ok(_) => {
+            // Valid escape code
+        }
+        Err(_) => {
+            errors.push(SyntaxError::new(MalformedUnicodeEscape, range));
+        }
     }
 }
 
@@ -205,9 +213,7 @@ mod test {
 
     #[test]
     fn test_valid_ascii_escape() {
-        let valid = [
-            r"\'", "\"", "\\\\", "\\\"", r"\n", r"\r", r"\t", r"\0", "a", "b",
-        ];
+        let valid = [r"\'", "\"", "\\\\", "\\\"", r"\n", r"\r", r"\t", r"\0"];
         for c in &valid {
             assert_valid_char(c);
         }
diff --git a/crates/ra_syntax/src/validation/mod.rs b/crates/ra_syntax/src/validation/mod.rs
index 2ff0bc26d..bdee8120c 100644
--- a/crates/ra_syntax/src/validation/mod.rs
+++ b/crates/ra_syntax/src/validation/mod.rs
@@ -5,6 +5,8 @@ use crate::{
     yellow::SyntaxError,
 };
 
+mod byte;
+mod byte_string;
 mod char;
 mod string;
 
@@ -12,6 +14,8 @@ pub(crate) fn validate(file: &SourceFileNode) -> Vec<SyntaxError> {
     let mut errors = Vec::new();
     for node in file.syntax().descendants() {
         let _ = visitor_ctx(&mut errors)
+            .visit::<ast::Byte, _>(self::byte::validate_byte_node)
+            .visit::<ast::ByteString, _>(self::byte_string::validate_byte_string_node)
             .visit::<ast::Char, _>(self::char::validate_char_node)
             .visit::<ast::String, _>(self::string::validate_string_node)
             .accept(node);
diff --git a/crates/ra_syntax/src/yellow/syntax_error.rs b/crates/ra_syntax/src/yellow/syntax_error.rs
index cf7b1d495..c32ee650d 100644
--- a/crates/ra_syntax/src/yellow/syntax_error.rs
+++ b/crates/ra_syntax/src/yellow/syntax_error.rs
@@ -72,6 +72,16 @@ pub enum SyntaxErrorKind {
     EmptyChar,
     UnclosedChar,
     OverlongChar,
+    EmptyByte,
+    UnclosedByte,
+    OverlongByte,
+    ByteOutOfRange,
+    UnescapedByte,
+    EmptyByteEscape,
+    InvalidByteEscape,
+    TooShortByteCodeEscape,
+    MalformedByteCodeEscape,
+    UnicodeEscapeForbidden,
     EmptyAsciiEscape,
     InvalidAsciiEscape,
     TooShortAsciiCodeEscape,
@@ -98,6 +108,19 @@ impl fmt::Display for SyntaxErrorKind {
             EmptyChar => write!(f, "Empty char literal"),
             UnclosedChar => write!(f, "Unclosed char literal"),
             OverlongChar => write!(f, "Char literal should be one character long"),
+            EmptyByte => write!(f, "Empty byte literal"),
+            UnclosedByte => write!(f, "Unclosed byte literal"),
+            OverlongByte => write!(f, "Byte literal should be one character long"),
+            ByteOutOfRange => write!(f, "Byte should be a valid ASCII character"),
+            UnescapedByte => write!(f, "This byte should always be escaped"),
+            EmptyByteEscape => write!(f, "Empty escape sequence"),
+            InvalidByteEscape => write!(f, "Invalid escape sequence"),
+            TooShortByteCodeEscape => write!(f, "Escape sequence should have two digits"),
+            MalformedByteCodeEscape => write!(f, "Escape sequence should be a hexadecimal number"),
+            UnicodeEscapeForbidden => write!(
+                f,
+                "Unicode escapes are not allowed in byte literals or byte strings"
+            ),
             TooShortAsciiCodeEscape => write!(f, "Escape sequence should have two digits"),
             AsciiCodeEscapeOutOfRange => {
                 write!(f, "Escape sequence should be between \\x00 and \\x7F")