1 files changed, 202 insertions, 0 deletions

diff --git a/crates/ra_syntax/src/validation/byte.rs b/crates/ra_syntax/src/validation/byte.rs
new file mode 100644
index 000000000..3d2806c4e
--- /dev/null
+++ b/crates/ra_syntax/src/validation/byte.rs
@@ -0,0 +1,202 @@
+//! 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();
+
+        use self::CharComponentKind::*;
+        match component.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));
+                }
+            }
+        }
+    }
+
+    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));
+    }
+}
+
+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", "a", "b",
+        ];
+        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);
+        }
+    }
+}