condtional multi-unwrap and guard clauses

compiler/parser/parser.odin

@@ -1129,16 +1129,39 @@ parse_if :: proc(parser: ^Parser) -> ast.Stmt_Id {
 	parser.no_struct_literal = true
 	condition := parse_expression(parser)
 	parser.no_struct_literal = saved
-	binding := symbol.INVALID
+	captures: [dynamic]symbol.Id
+	captures.allocator = parser.module.allocator
+	guard := ast.INVALID_EXPR
 	if _, ok := allow(parser, .Pipe); ok {
-		name_tok, name_ok := allow(parser, .Identifier)
-		if name_ok {
-			binding = name_tok.symbol
-		} else {
-			source.add(parser.diagnostics, current(parser).span, "expected a binding name after '|'")
+		for {
+			name_tok := current(parser)
+			if name_tok.kind == .Identifier || name_tok.kind == .Underscore {
+				advance(parser)
+				append(&captures, name_tok.symbol)
+			} else {
+				source.add(parser.diagnostics, current(parser).span, "expected an unwrap capture name")
+				break
+			}
+			if _, comma_ok := allow(parser, .Comma); !comma_ok {
+				break
+			}
+			if current(parser).kind == .Colon || current(parser).kind == .Pipe {
+				source.add(parser.diagnostics, current(parser).span, "expected an unwrap capture after ','")
+				break
+			}
+		}
+		if _, guard_ok := allow(parser, .Colon); guard_ok {
+			if current(parser).kind == .Pipe {
+				source.add(parser.diagnostics, current(parser).span, "expected a guard expression after ':'")
+			} else {
+				saved = parser.no_struct_literal
+				parser.no_struct_literal = true
+				guard = parse_expression(parser)
+				parser.no_struct_literal = saved
+			}
 		}
 		if _, close_ok := allow(parser, .Pipe); !close_ok {
-			source.add(parser.diagnostics, current(parser).span, "expected '|' to close the unwrap binding")
+			source.add(parser.diagnostics, current(parser).span, "expected '|' to close unwrap captures")
 		}
 	}
 	skip_newlines(parser)
@@ -1164,8 +1187,9 @@ parse_if :: proc(parser: ^Parser) -> ast.Stmt_Id {
 	append(&parser.module.statements, ast.Stmt{
 		kind=.If,
 		span=span_from(start.span, previous(parser).span),
-		name=binding,
 		expr=condition,
+		captures=captures[:],
+		guard=guard,
 		body=then_body,
 		else_body=else_body,
 		diagnostic=source.INVALID_DIAGNOSTIC,