3 files changed, 458 insertions, 0 deletions

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",
+        );
+    }
+}