Merge #222

222: Validate string literals r=aochagavia a=aochagavia

Related: #6 (some validators are still missing), fixes #27

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

9 files changed, 621 insertions, 274 deletions

diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index 5b5f71ee7..2e9ae263a 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -3236,6 +3236,43 @@ impl<'a> AstNode<'a> for Stmt<'a> {
 
 impl<'a> Stmt<'a> {}
 
+// String
+#[derive(Debug, Clone, Copy,)]
+pub struct StringNode<R: TreeRoot<RaTypes> = OwnedRoot> {
+    pub(crate) syntax: SyntaxNode<R>,
+}
+pub type String<'a> = StringNode<RefRoot<'a>>;
+
+impl<R1: TreeRoot<RaTypes>, R2: TreeRoot<RaTypes>> PartialEq<StringNode<R1>> for StringNode<R2> {
+    fn eq(&self, other: &StringNode<R1>) -> bool { self.syntax == other.syntax }
+}
+impl<R: TreeRoot<RaTypes>> Eq for StringNode<R> {}
+impl<R: TreeRoot<RaTypes>> Hash for StringNode<R> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.syntax.hash(state) }
+}
+
+impl<'a> AstNode<'a> for String<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            STRING => Some(String { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<R: TreeRoot<RaTypes>> StringNode<R> {
+    pub fn borrowed(&self) -> String {
+        StringNode { syntax: self.syntax.borrowed() }
+    }
+    pub fn owned(&self) -> StringNode {
+        StringNode { syntax: self.syntax.owned() }
+    }
+}
+
+
+impl<'a> String<'a> {}
+
 // StructDef
 #[derive(Debug, Clone, Copy,)]
 pub struct StructDefNode<R: TreeRoot<RaTypes> = OwnedRoot> {
diff --git a/crates/ra_syntax/src/ast/mod.rs b/crates/ra_syntax/src/ast/mod.rs
index 6b0d62610..f20714ede 100644
--- a/crates/ra_syntax/src/ast/mod.rs
+++ b/crates/ra_syntax/src/ast/mod.rs
@@ -1,6 +1,7 @@
 mod generated;
 
 use std::marker::PhantomData;
+use std::string::String as RustString;
 
 use itertools::Itertools;
 
@@ -76,7 +77,7 @@ pub trait DocCommentsOwner<'a>: AstNode<'a> {
 
     /// Returns the textual content of a doc comment block as a single string.
     /// That is, strips leading `///` and joins lines
-    fn doc_comment_text(self) -> String {
+    fn doc_comment_text(self) -> RustString {
         self.doc_comments()
             .map(|comment| {
                 let prefix = comment.prefix();
@@ -133,6 +134,12 @@ impl<'a> Char<'a> {
     }
 }
 
+impl<'a> String<'a> {
+    pub fn text(&self) -> &SmolStr {
+        &self.syntax().leaf_text().unwrap()
+    }
+}
+
 impl<'a> Comment<'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 a92844415..c3184667e 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -411,6 +411,7 @@ Grammar(
         "PrefixExpr": (),
         "RangeExpr": (),
         "BinExpr": (),
+        "String": (),
         "Char": (),
         "Literal": (),
 
diff --git a/crates/ra_syntax/src/string_lexing/mod.rs b/crates/ra_syntax/src/string_lexing.rs
index cc53e0aba..d613bb042 100644
--- a/crates/ra_syntax/src/string_lexing/mod.rs
+++ b/crates/ra_syntax/src/string_lexing.rs
@@ -1,6 +1,68 @@
 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),
@@ -93,6 +155,12 @@ impl<'a> Parser<'a> {
         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()
     }
@@ -172,6 +240,51 @@ impl<'a> Parser<'a> {
             ))
         }
     }
+
+    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)]
diff --git a/crates/ra_syntax/src/validation.rs b/crates/ra_syntax/src/validation.rs
deleted file mode 100644
index a10b297c0..000000000
--- a/crates/ra_syntax/src/validation.rs
+++ /dev/null
@@ -1,271 +0,0 @@
-use std::u32;
-
-use arrayvec::ArrayString;
-
-use crate::{
-    algo::visit::{visitor_ctx, VisitorCtx},
-    ast::{self, AstNode},
-    SourceFileNode,
-    string_lexing::{self, CharComponentKind},
-    yellow::{
-        SyntaxError,
-        SyntaxErrorKind::*,
-    },
-};
-
-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::Char, _>(validate_char)
-            .accept(node);
-    }
-    errors
-}
-
-fn validate_char(node: ast::Char, errors: &mut Vec<SyntaxError>) {
-    let mut components = string_lexing::parse_char_literal(node.text());
-    let mut len = 0;
-    for component in &mut components {
-        len += 1;
-
-        // Validate escapes
-        let text = &node.text()[component.range];
-        let range = component.range + node.syntax().range().start();
-        use self::CharComponentKind::*;
-        match component.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));
-                    }
-                }
-            }
-            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)),
-                    }
-                }
-            }
-            UnicodeEscape => {
-                assert!(&text[..2] == "\\u", "UnicodeEscape always starts with \\u");
-
-                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;
-                        }
-
-                        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;
-                    }
-                }
-
-                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));
-                    }
-                }
-            }
-            CodePoint => {
-                // These code points must always be escaped
-                if text == "\t" || text == "\r" {
-                    errors.push(SyntaxError::new(UnescapedCodepoint, range));
-                }
-            }
-        }
-    }
-
-    if !components.has_closing_quote {
-        errors.push(SyntaxError::new(UnclosedChar, node.syntax().range()));
-    }
-
-    if len == 0 {
-        errors.push(SyntaxError::new(EmptyChar, node.syntax().range()));
-    }
-
-    if len > 1 {
-        errors.push(SyntaxError::new(LongChar, node.syntax().range()));
-    }
-}
-
-fn is_ascii_escape(code: char) -> bool {
-    match code {
-        '\\' | '\'' | '"' | 'n' | 'r' | 't' | '0' => true,
-        _ => false,
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use crate::SourceFileNode;
-
-    fn build_file(literal: &str) -> SourceFileNode {
-        let src = format!("const C: char = '{}';", literal);
-        SourceFileNode::parse(&src)
-    }
-
-    fn assert_valid_char(literal: &str) {
-        let file = build_file(literal);
-        assert!(
-            file.errors().len() == 0,
-            "Errors for literal '{}': {:?}",
-            literal,
-            file.errors()
-        );
-    }
-
-    fn assert_invalid_char(literal: &str) {
-        let file = build_file(literal);
-        assert!(file.errors().len() > 0);
-    }
-
-    #[test]
-    fn test_ansi_codepoints() {
-        for byte in 0..=255u8 {
-            match byte {
-                b'\n' | b'\r' | b'\t' => assert_invalid_char(&(byte as char).to_string()),
-                b'\'' | b'\\' => { /* Ignore character close and backslash */ }
-                _ => assert_valid_char(&(byte as char).to_string()),
-            }
-        }
-    }
-
-    #[test]
-    fn test_unicode_codepoints() {
-        let valid = ["Ƒ", "バ", "メ", "﷽"];
-        for c in &valid {
-            assert_valid_char(c);
-        }
-    }
-
-    #[test]
-    fn test_unicode_multiple_codepoints() {
-        let invalid = ["नी", "👨‍👨‍"];
-        for c in &invalid {
-            assert_invalid_char(c);
-        }
-    }
-
-    #[test]
-    fn test_valid_ascii_escape() {
-        let valid = [
-            r"\'", "\"", "\\\\", "\\\"", r"\n", r"\r", r"\t", r"\0", "a", "b",
-        ];
-        for c in &valid {
-            assert_valid_char(c);
-        }
-    }
-
-    #[test]
-    fn test_invalid_ascii_escape() {
-        let invalid = [r"\a", r"\?", r"\"];
-        for c in &invalid {
-            assert_invalid_char(c);
-        }
-    }
-
-    #[test]
-    fn test_valid_ascii_code_escape() {
-        let valid = [r"\x00", r"\x7F", r"\x55"];
-        for c in &valid {
-            assert_valid_char(c);
-        }
-    }
-
-    #[test]
-    fn test_invalid_ascii_code_escape() {
-        let invalid = [r"\x", r"\x7", r"\xF0"];
-        for c in &invalid {
-            assert_invalid_char(c);
-        }
-    }
-
-    #[test]
-    fn test_valid_unicode_escape() {
-        let valid = [
-            r"\u{FF}",
-            r"\u{0}",
-            r"\u{F}",
-            r"\u{10FFFF}",
-            r"\u{1_0__FF___FF_____}",
-        ];
-        for c in &valid {
-            assert_valid_char(c);
-        }
-    }
-
-    #[test]
-    fn test_invalid_unicode_escape() {
-        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_char(c);
-        }
-    }
-}
diff --git a/crates/ra_syntax/src/validation/char.rs b/crates/ra_syntax/src/validation/char.rs
new file mode 100644
index 000000000..63f9bad24
--- /dev/null
+++ b/crates/ra_syntax/src/validation/char.rs
@@ -0,0 +1,270 @@
+use std::u32;
+
+use arrayvec::ArrayString;
+
+use crate::{
+    ast::{self, AstNode},
+    string_lexing::{self, CharComponentKind},
+    TextRange,
+    yellow::{
+        SyntaxError,
+        SyntaxErrorKind::*,
+    },
+};
+
+pub(crate) 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);
+    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_char_component(text, component.kind, range, errors);
+    }
+
+    if !components.has_closing_quote {
+        errors.push(SyntaxError::new(UnclosedChar, literal_range));
+    }
+
+    if len == 0 {
+        errors.push(SyntaxError::new(EmptyChar, literal_range));
+    }
+
+    if len > 1 {
+        errors.push(SyntaxError::new(OverlongChar, literal_range));
+    }
+}
+
+pub(crate) fn validate_char_component(
+    text: &str,
+    kind: CharComponentKind,
+    range: TextRange,
+    errors: &mut Vec<SyntaxError>,
+) {
+    // 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));
+                }
+            }
+        }
+        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)),
+                }
+            }
+        }
+        UnicodeEscape => {
+            assert!(&text[..2] == "\\u", "UnicodeEscape always starts with \\u");
+
+            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;
+                    }
+
+                    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;
+                }
+            }
+
+            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));
+                }
+            }
+        }
+        CodePoint => {
+            // These code points must always be escaped
+            if text == "\t" || text == "\r" {
+                errors.push(SyntaxError::new(UnescapedCodepoint, range));
+            }
+        }
+    }
+}
+
+fn is_ascii_escape(code: char) -> bool {
+    match code {
+        '\\' | '\'' | '"' | 'n' | 'r' | 't' | '0' => true,
+        _ => false,
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::SourceFileNode;
+
+    fn build_file(literal: &str) -> SourceFileNode {
+        let src = format!("const C: char = '{}';", literal);
+        SourceFileNode::parse(&src)
+    }
+
+    fn assert_valid_char(literal: &str) {
+        let file = build_file(literal);
+        assert!(
+            file.errors().len() == 0,
+            "Errors for literal '{}': {:?}",
+            literal,
+            file.errors()
+        );
+    }
+
+    fn assert_invalid_char(literal: &str) {
+        let file = build_file(literal);
+        assert!(file.errors().len() > 0);
+    }
+
+    #[test]
+    fn test_ansi_codepoints() {
+        for byte in 0..=255u8 {
+            match byte {
+                b'\n' | b'\r' | b'\t' => assert_invalid_char(&(byte as char).to_string()),
+                b'\'' | b'\\' => { /* Ignore character close and backslash */ }
+                _ => assert_valid_char(&(byte as char).to_string()),
+            }
+        }
+    }
+
+    #[test]
+    fn test_unicode_codepoints() {
+        let valid = ["Ƒ", "バ", "メ", "﷽"];
+        for c in &valid {
+            assert_valid_char(c);
+        }
+    }
+
+    #[test]
+    fn test_unicode_multiple_codepoints() {
+        let invalid = ["नी", "👨‍👨‍"];
+        for c in &invalid {
+            assert_invalid_char(c);
+        }
+    }
+
+    #[test]
+    fn test_valid_ascii_escape() {
+        let valid = [
+            r"\'", "\"", "\\\\", "\\\"", r"\n", r"\r", r"\t", r"\0", "a", "b",
+        ];
+        for c in &valid {
+            assert_valid_char(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_ascii_escape() {
+        let invalid = [r"\a", r"\?", r"\"];
+        for c in &invalid {
+            assert_invalid_char(c);
+        }
+    }
+
+    #[test]
+    fn test_valid_ascii_code_escape() {
+        let valid = [r"\x00", r"\x7F", r"\x55"];
+        for c in &valid {
+            assert_valid_char(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_ascii_code_escape() {
+        let invalid = [r"\x", r"\x7", r"\xF0"];
+        for c in &invalid {
+            assert_invalid_char(c);
+        }
+    }
+
+    #[test]
+    fn test_valid_unicode_escape() {
+        let valid = [
+            r"\u{FF}",
+            r"\u{0}",
+            r"\u{F}",
+            r"\u{10FFFF}",
+            r"\u{1_0__FF___FF_____}",
+        ];
+        for c in &valid {
+            assert_valid_char(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_unicode_escape() {
+        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_char(c);
+        }
+    }
+}
diff --git a/crates/ra_syntax/src/validation/mod.rs b/crates/ra_syntax/src/validation/mod.rs
new file mode 100644
index 000000000..2ff0bc26d
--- /dev/null
+++ b/crates/ra_syntax/src/validation/mod.rs
@@ -0,0 +1,20 @@
+use crate::{
+    algo::visit::{visitor_ctx, VisitorCtx},
+    ast,
+    SourceFileNode,
+    yellow::SyntaxError,
+};
+
+mod char;
+mod string;
+
+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::Char, _>(self::char::validate_char_node)
+            .visit::<ast::String, _>(self::string::validate_string_node)
+            .accept(node);
+    }
+    errors
+}
diff --git a/crates/ra_syntax/src/validation/string.rs b/crates/ra_syntax/src/validation/string.rs
new file mode 100644
index 000000000..089879d15
--- /dev/null
+++ b/crates/ra_syntax/src/validation/string.rs
@@ -0,0 +1,168 @@
+use crate::{
+    ast::{self, AstNode},
+    string_lexing::{self, StringComponentKind},
+    yellow::{
+        SyntaxError,
+        SyntaxErrorKind::*,
+    },
+};
+
+use super::char;
+
+pub(crate) fn validate_string_node(node: ast::String, errors: &mut Vec<SyntaxError>) {
+    let literal_text = node.text();
+    let literal_range = node.syntax().range();
+    let mut components = string_lexing::parse_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 */ }
+                    _ => char::validate_char_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 str = "{}";"#, 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..=255u8 {
+            match byte {
+                b'\"' | b'\\' => { /* Ignore string close and backslash */ }
+                _ => assert_valid_str(&(byte as char).to_string()),
+            }
+        }
+    }
+
+    #[test]
+    fn test_unicode_codepoints() {
+        let valid = ["Ƒ", "バ", "メ", "﷽"];
+        for c in &valid {
+            assert_valid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_unicode_multiple_codepoints() {
+        let valid = ["नी", "👨‍👨‍"];
+        for c in &valid {
+            assert_valid_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"];
+        for c in &valid {
+            assert_valid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_ascii_code_escape() {
+        let invalid = [r"\x", r"\x7", r"\xF0"];
+        for c in &invalid {
+            assert_invalid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_valid_unicode_escape() {
+        let valid = [
+            r"\u{FF}",
+            r"\u{0}",
+            r"\u{F}",
+            r"\u{10FFFF}",
+            r"\u{1_0__FF___FF_____}",
+        ];
+        for c in &valid {
+            assert_valid_str(c);
+        }
+    }
+
+    #[test]
+    fn test_invalid_unicode_escape() {
+        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() {
+        assert_valid_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_ignore_newline() {
+        assert_valid_str(
+            "Hello \
+             World",
+        );
+    }
+}
diff --git a/crates/ra_syntax/src/yellow/syntax_error.rs b/crates/ra_syntax/src/yellow/syntax_error.rs
index c524adf39..cf7b1d495 100644
--- a/crates/ra_syntax/src/yellow/syntax_error.rs
+++ b/crates/ra_syntax/src/yellow/syntax_error.rs
@@ -71,7 +71,7 @@ pub enum SyntaxErrorKind {
     UnescapedCodepoint,
     EmptyChar,
     UnclosedChar,
-    LongChar,
+    OverlongChar,
     EmptyAsciiEscape,
     InvalidAsciiEscape,
     TooShortAsciiCodeEscape,
@@ -82,6 +82,7 @@ pub enum SyntaxErrorKind {
     EmptyUnicodeEcape,
     OverlongUnicodeEscape,
     UnicodeEscapeOutOfRange,
+    UnclosedString,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -96,7 +97,7 @@ impl fmt::Display for SyntaxErrorKind {
             InvalidAsciiEscape => write!(f, "Invalid escape sequence"),
             EmptyChar => write!(f, "Empty char literal"),
             UnclosedChar => write!(f, "Unclosed char literal"),
-            LongChar => write!(f, "Char literal should be one character long"),
+            OverlongChar => write!(f, "Char literal should be one character long"),
             TooShortAsciiCodeEscape => write!(f, "Escape sequence should have two digits"),
             AsciiCodeEscapeOutOfRange => {
                 write!(f, "Escape sequence should be between \\x00 and \\x7F")
@@ -109,6 +110,7 @@ impl fmt::Display for SyntaxErrorKind {
                 write!(f, "Unicode escape sequence should have at most 6 digits")
             }
             UnicodeEscapeOutOfRange => write!(f, "Unicode escape code should be at most 0x10FFFF"),
+            UnclosedString => write!(f, "Unclosed string literal"),
             ParseError(msg) => write!(f, "{}", msg.0),
         }
     }