1 files changed, 213 insertions, 0 deletions

diff --git a/crates/ra_syntax/src/lexer.rs b/crates/ra_syntax/src/lexer.rs
new file mode 100644
index 000000000..f388da273
--- /dev/null
+++ b/crates/ra_syntax/src/lexer.rs
@@ -0,0 +1,213 @@
+mod classes;
+mod comments;
+mod numbers;
+mod ptr;
+mod strings;
+
+use crate::{
+    SyntaxKind::{self, *},
+    TextUnit,
+};
+
+use self::{
+    classes::*,
+    comments::{scan_comment, scan_shebang},
+    numbers::scan_number,
+    ptr::Ptr,
+    strings::{
+        is_string_literal_start, scan_byte_char_or_string, scan_char, scan_raw_string, scan_string,
+    },
+};
+
+/// A token of Rust source.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Token {
+    /// The kind of token.
+    pub kind: SyntaxKind,
+    /// The length of the token.
+    pub len: TextUnit,
+}
+
+/// Break a string up into its component tokens
+pub fn tokenize(text: &str) -> Vec<Token> {
+    let mut text = text;
+    let mut acc = Vec::new();
+    while !text.is_empty() {
+        let token = next_token(text);
+        acc.push(token);
+        let len: u32 = token.len.into();
+        text = &text[len as usize..];
+    }
+    acc
+}
+
+/// Get the next token from a string
+pub fn next_token(text: &str) -> Token {
+    assert!(!text.is_empty());
+    let mut ptr = Ptr::new(text);
+    let c = ptr.bump().unwrap();
+    let kind = next_token_inner(c, &mut ptr);
+    let len = ptr.into_len();
+    Token { kind, len }
+}
+
+fn next_token_inner(c: char, ptr: &mut Ptr) -> SyntaxKind {
+    if is_whitespace(c) {
+        ptr.bump_while(is_whitespace);
+        return WHITESPACE;
+    }
+
+    match c {
+        '#' => {
+            if scan_shebang(ptr) {
+                return SHEBANG;
+            }
+        }
+        '/' => {
+            if let Some(kind) = scan_comment(ptr) {
+                return kind;
+            }
+        }
+        _ => (),
+    }
+
+    let ident_start = is_ident_start(c) && !is_string_literal_start(c, ptr.current(), ptr.nth(1));
+    if ident_start {
+        return scan_ident(c, ptr);
+    }
+
+    if is_dec_digit(c) {
+        let kind = scan_number(c, ptr);
+        scan_literal_suffix(ptr);
+        return kind;
+    }
+
+    // One-byte tokens.
+    if let Some(kind) = SyntaxKind::from_char(c) {
+        return kind;
+    }
+
+    match c {
+        // Multi-byte tokens.
+        '.' => {
+            return match (ptr.current(), ptr.nth(1)) {
+                (Some('.'), Some('.')) => {
+                    ptr.bump();
+                    ptr.bump();
+                    DOTDOTDOT
+                }
+                (Some('.'), Some('=')) => {
+                    ptr.bump();
+                    ptr.bump();
+                    DOTDOTEQ
+                }
+                (Some('.'), _) => {
+                    ptr.bump();
+                    DOTDOT
+                }
+                _ => DOT,
+            };
+        }
+        ':' => {
+            return match ptr.current() {
+                Some(':') => {
+                    ptr.bump();
+                    COLONCOLON
+                }
+                _ => COLON,
+            };
+        }
+        '=' => {
+            return match ptr.current() {
+                Some('=') => {
+                    ptr.bump();
+                    EQEQ
+                }
+                Some('>') => {
+                    ptr.bump();
+                    FAT_ARROW
+                }
+                _ => EQ,
+            };
+        }
+        '!' => {
+            return match ptr.current() {
+                Some('=') => {
+                    ptr.bump();
+                    NEQ
+                }
+                _ => EXCL,
+            };
+        }
+        '-' => {
+            return if ptr.at('>') {
+                ptr.bump();
+                THIN_ARROW
+            } else {
+                MINUS
+            };
+        }
+
+        // If the character is an ident start not followed by another single
+        // quote, then this is a lifetime name:
+        '\'' => {
+            return if ptr.at_p(is_ident_start) && !ptr.at_str("''") {
+                ptr.bump();
+                while ptr.at_p(is_ident_continue) {
+                    ptr.bump();
+                }
+                // lifetimes shouldn't end with a single quote
+                // if we find one, then this is an invalid character literal
+                if ptr.at('\'') {
+                    ptr.bump();
+                    return CHAR; // TODO: error reporting
+                }
+                LIFETIME
+            } else {
+                scan_char(ptr);
+                scan_literal_suffix(ptr);
+                CHAR
+            };
+        }
+        'b' => {
+            let kind = scan_byte_char_or_string(ptr);
+            scan_literal_suffix(ptr);
+            return kind;
+        }
+        '"' => {
+            scan_string(ptr);
+            scan_literal_suffix(ptr);
+            return STRING;
+        }
+        'r' => {
+            scan_raw_string(ptr);
+            scan_literal_suffix(ptr);
+            return RAW_STRING;
+        }
+        _ => (),
+    }
+    ERROR
+}
+
+fn scan_ident(c: char, ptr: &mut Ptr) -> SyntaxKind {
+    let is_single_letter = match ptr.current() {
+        None => true,
+        Some(c) if !is_ident_continue(c) => true,
+        _ => false,
+    };
+    if is_single_letter {
+        return if c == '_' { UNDERSCORE } else { IDENT };
+    }
+    ptr.bump_while(is_ident_continue);
+    if let Some(kind) = SyntaxKind::from_keyword(ptr.current_token_text()) {
+        return kind;
+    }
+    IDENT
+}
+
+fn scan_literal_suffix(ptr: &mut Ptr) {
+    if ptr.at_p(is_ident_start) {
+        ptr.bump();
+    }
+    ptr.bump_while(is_ident_continue);
+}