v0.3.0: restructure directories

- src/        ← compiler/selfhost/  (canonical Bux compiler)
- bootstrap/  ← compiler/bootstrap/ (Nim bootstrap)
- lib/        ← library/std/        (standard library)
- rt/         ← library/runtime/    (C runtime)
- tests/      ← compiler/tests/     (unit tests)
- Remove _selfhost/ (built into build/selfhost/ now)
- Update all path references (Makefile, cli.nim, cli.bux, docs)
- Bump version to 0.3.0

tests/lexer_test.nim

@@ -0,0 +1,124 @@
+import std/[unittest, os, strutils]
+import ../bootstrap/[lexer, token, source_location]
+
+proc tokenKinds(source: string): seq[TokenKind] =
+  let res = tokenize(source, "<test>")
+  for t in res.tokens:
+    result.add(t.kind)
+
+proc tokenTexts(source: string): seq[string] =
+  let res = tokenize(source, "<test>")
+  for t in res.tokens:
+    result.add(t.text)
+
+suite "Lexer":
+  test "empty source":
+    let res = tokenize("", "<test>")
+    check res.tokens.len == 1
+    check res.tokens[0].kind == tkEndOfFile
+    check not res.hasErrors
+
+  test "simple identifiers":
+    let kinds = tokenKinds("foo bar _x Baz123")
+    check kinds == @[tkIdent, tkIdent, tkIdent, tkIdent, tkEndOfFile]
+
+  test "keywords":
+    let kinds = tokenKinds("func let var if else while for return match struct enum")
+    check kinds == @[tkFunc, tkLet, tkVar, tkIf, tkElse, tkWhile, tkFor, tkReturn, tkMatch, tkStruct, tkEnum, tkEndOfFile]
+
+  test "bool literals":
+    let kinds = tokenKinds("true false")
+    check kinds == @[tkBoolLiteral, tkBoolLiteral, tkEndOfFile]
+    let texts = tokenTexts("true false")
+    check texts == @["true", "false", ""]
+
+  test "integers":
+    let kinds = tokenKinds("42 0xFF 0b1010 0o77")
+    check kinds == @[tkIntLiteral, tkIntLiteral, tkIntLiteral, tkIntLiteral, tkEndOfFile]
+
+  test "floats":
+    let kinds = tokenKinds("3.14 1.0e-9 2.5E+3")
+    check kinds == @[tkFloatLiteral, tkFloatLiteral, tkFloatLiteral, tkEndOfFile]
+
+  test "operators":
+    let kinds = tokenKinds("+ - * / % ** ++ --")
+    check kinds == @[tkPlus, tkMinus, tkStar, tkSlash, tkPercent, tkStarStar, tkPlusPlus, tkMinusMinus, tkEndOfFile]
+
+  test "comparison operators":
+    let kinds = tokenKinds("== != < <= > >=")
+    check kinds == @[tkEq, tkNe, tkLt, tkLe, tkGt, tkGe, tkEndOfFile]
+
+  test "assignment operators":
+    let kinds = tokenKinds("= += -= *= /= %= &= |= ^= <<= >>=")
+    check kinds == @[tkAssign, tkPlusAssign, tkMinusAssign, tkStarAssign, tkSlashAssign, tkPercentAssign, tkAmpAssign, tkPipeAssign, tkCaretAssign, tkShlAssign, tkShrAssign, tkEndOfFile]
+
+  test "punctuation":
+    let kinds = tokenKinds("( ) { } [ ] , ; : :: . .. ... ..= -> => @ # ?")
+    check kinds == @[tkLParen, tkRParen, tkLBrace, tkRBrace, tkLBracket, tkRBracket, tkComma, tkSemicolon, tkColon, tkColonColon, tkDot, tkDotDot, tkDotDotDot, tkDotDotEqual, tkArrow, tkFatArrow, tkAt, tkHash, tkQuestion, tkEndOfFile]
+
+  test "logical operators":
+    let kinds = tokenKinds("&& || !")
+    check kinds == @[tkAmpAmp, tkPipePipe, tkBang, tkEndOfFile]
+
+  test "bitwise operators":
+    let kinds = tokenKinds("& | ^ ~ << >>")
+    check kinds == @[tkAmp, tkPipe, tkCaret, tkTilde, tkShl, tkShr, tkEndOfFile]
+
+  test "string literals":
+    let kinds = tokenKinds("\"hello\" c8\"world\"")
+    check kinds == @[tkStringLiteral, tkStringLiteral, tkEndOfFile]
+
+  test "char literals":
+    let kinds = tokenKinds("'A' c8'B'")
+    check kinds == @[tkCharLiteral, tkCharLiteral, tkEndOfFile]
+
+  test "line comments are skipped":
+    let kinds = tokenKinds("let x = 42 // this is a comment")
+    check kinds == @[tkLet, tkIdent, tkAssign, tkIntLiteral, tkEndOfFile]
+
+  test "block comments are skipped":
+    let kinds = tokenKinds("let /* inline comment */ x = 42")
+    check kinds == @[tkLet, tkIdent, tkAssign, tkIntLiteral, tkEndOfFile]
+
+  test "nested block comments":
+    let kinds = tokenKinds("let /* outer /* inner */ still outer */ x = 42")
+    check kinds == @[tkLet, tkIdent, tkAssign, tkIntLiteral, tkEndOfFile]
+
+  test "intrinsics":
+    let kinds = tokenKinds("#line #column #file #function #date #time #module")
+    check kinds == @[tkHashLine, tkHashColumn, tkHashFile, tkHashFunction, tkHashDate, tkHashTime, tkHashModule, tkEndOfFile]
+
+  test "newline tokens":
+    let kinds = tokenKinds("let x = 42\nlet y = 10")
+    check kinds == @[tkLet, tkIdent, tkAssign, tkIntLiteral, tkNewLine, tkLet, tkIdent, tkAssign, tkIntLiteral, tkEndOfFile]
+
+  test "paths":
+    let kinds = tokenKinds("Std::Io::PrintLine")
+    check kinds == @[tkIdent, tkColonColon, tkIdent, tkColonColon, tkIdent, tkEndOfFile]
+
+  test "unterminated string error":
+    let res = tokenize("\"hello", "<test>")
+    check res.hasErrors
+
+  test "unterminated char error":
+    let res = tokenize("'a", "<test>")
+    check res.hasErrors
+
+  test "escape sequences in string":
+    let res = tokenize("\"hello\\nworld\\t!\"", "<test>")
+    check not res.hasErrors
+    check res.tokens[0].kind == tkStringLiteral
+
+  test "full function":
+    let src = "func Main() -> int {\n    let x: int32 = 42;\n    return x;\n}\n"
+    let res = tokenize(src, "<test>")
+    check not res.hasErrors
+    check res.tokens[0].kind == tkFunc
+    check res.tokens[1].kind == tkIdent
+    check res.tokens[1].text == "Main"
+
+  test "dumpTokens produces output":
+    let res = tokenize("let x = 42", "<test>")
+    let dump = dumpTokens(res)
+    check "let" in dump
+    check "42" in dump