052 pattern branches

✓ Passing This code compiles and runs correctly.

Code

// ============================================================================
// TEST: Pattern Branches Parser Support
// ============================================================================
// Verifies that the parser correctly handles [...] pattern branch syntax.
// Pattern branches allow opaque expressions as branch names for DSL transforms.
//
// The [...] content is passed through as the branch name - transforms interpret it.
// ============================================================================

// Simple event to test pattern branches
~event test_patterns {}
| ok {}

~proc test_patterns {
    return .{ .ok = .{} };
}

// Test that pattern branches parse correctly
// The branch names are [GET /users/:id] etc - opaque to the compiler
~test_patterns()
| [GET /users/:id] |> ok {}
| [POST /users] |> ok {}
| [nested [brackets] work] |> ok {}
| [* -> stopped] |> ok {}  // State machine style
| ok |> _  // Normal branch still works

// Verify nested patterns work
~test_patterns()
| [/admin/*] |>
    test_patterns()
    | [GET /dashboard] |> ok {}
    | ok |> _
| ok |> _
input.kz

Error Verification

Expected Error Pattern

Pattern branches without a transform produce KORU021 errors.

This test verifies that pattern branch SYNTAX parses correctly.
The validation correctly rejects unknown branches like [GET /users/:id]
when the event only declares 'ok'.

Expected errors:
  - KORU021: unknown branch '[GET /users/:id]'
  - KORU021: unknown branch '[POST /users]'
  - etc.

Actual Compiler Output

[PHASE 2.4] Calling run_pass for transforms\n[PHASE 2.5] Executing comptime_main() - running comptime flows
[PHASE 2.5] Comptime flows complete (31 items)
[PHASE 2.6] Rescanning transformed AST (31 items)
[PHASE 2.6] Rescan complete: 25 comptime events found
  [0] std.compiler:requires
  [1] std.compiler:flag.declare
  [2] std.compiler:command.declare
  [3] std.compiler:coordinate
  [4] std.compiler:context_create
  [5] std.testing:test
  [6] std.testing:validate_mocks
  [7] std.testing:test.with_harness
  [8] std.testing:test.harness
  [9] std.testing:assert
  [10] std.testing:test.property.equivalent
  [11] std.deps:deps
  [12] std.deps:requires.system
  [13] std.deps:requires.zig
  [14] std.control:if
  [15] std.control:for
  [16] std.control:capture
  [17] std.control:const
  [18] std.build:requires
  [19] std.build:variants
  [20] std.build:config
  [21] std.build:command.sh
  [22] std.build:command.zig
  [23] std.build:step
  [24] std.template:define
error[KORU021]: continuation references unknown branch '[GET /users/:id]'
  --> structural_check:21:0

error[KORU021]: continuation references unknown branch '[POST /users]'
  --> structural_check:21:0

error[KORU021]: continuation references unknown branch '[nested [brackets] work]'
  --> structural_check:21:0

error[KORU021]: continuation references unknown branch '[* -> stopped]'
  --> structural_check:21:0

❌ Compiler coordination error: Incomplete branch coverage
error: CompilerCoordinationFailed
/Users/larsde/src/koru/tests/regression/200_COMPILER_FEATURES/210_PARSER/210_052_pattern_branches/backend.zig:9517:17: 0x104186433 in emit (backend)
                return error.CompilerCoordinationFailed;
                ^
/Users/larsde/src/koru/tests/regression/200_COMPILER_FEATURES/210_PARSER/210_052_pattern_branches/backend.zig:9601:28: 0x1041871bf in main (backend)
    const generated_code = try RuntimeEmitter.emit(compile_allocator, final_ast);
                           ^

Test Configuration

MUST_FAIL