allow keywords as values in enums (and tagged unions)

compiler_tests.odin

@@ -10223,6 +10223,93 @@ main func() i32 {
 	testing.expect(t, found_promotion)
 }
 
+@(test)
+keywords_are_valid_enum_members_and_tagged_union_variants :: proc(t: ^testing.T) {
+	testing.expect(t, token.is_keyword(.Keyword_Func))
+	testing.expect(t, token.is_keyword(.Keyword_C_Longdouble))
+	testing.expect(t, !token.is_keyword(.Identifier))
+	testing.expect(t, !token.is_keyword(.Underscore))
+
+	text := `TokenKind :: enum {
+	if
+	else
+	return
+}
+Token :: union(TokenKind) {
+	if i32
+	else void
+	return i32
+}
+kind func(value bool) TokenKind {
+	if value {
+		return .if
+	}
+	return TokenKind.else
+}
+main func() i32 {
+	first TokenKind = kind(true)
+	second TokenKind = .return
+	a Token = Token{ if = 1 }
+	b Token = Token{ else }
+	c Token = .return{2}
+	total i32 = a.if + c.return
+	match first {
+		.if: total = total + 1
+		.else: total = total + 2
+		.return: total = total + 3
+	}
+	match b {
+		.if |value|: total = total + value
+		.else: total = total + 4
+		.return |value|: total = total + value
+	}
+	_ = second
+	return total
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+	ir_module := lower.lower(&hir_module)
+	defer ir.destroy_module(&ir_module)
+	llvm_text := llvm.emit(&ir_module, &diagnostics, &symbols)
+	defer delete(llvm_text)
+
+	testing.expect_value(t, len(diagnostics.items), 0)
+	testing.expect(t, len(llvm_text) > 0)
+}
+
+@(test)
+keyword_names_remain_invalid_for_struct_fields :: proc(t: ^testing.T) {
+	text := `Bad :: struct {
+	if i32
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&module)
+
+	found := false
+	for diagnostic in diagnostics.items {
+		found = found || strings.contains(diagnostic.message, "expected a struct field name")
+	}
+	testing.expect(t, found)
+}
+
 @(test)
 unbacked_enum_uses_global_u16_backing :: proc(t: ^testing.T) {
 	builder := strings.builder_make()