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Debug Tools

AILANG provides several CLI tools for understanding the compilation pipeline and diagnosing issues.

Quick Reference​

CommandPurpose
ailang debug ast <file>Show Core AST (ANF) structure
ailang check -debug-compile <file>Show compilation phase timing and lowering telemetry
ailang check -timeout 30s <file>Detect compilation hangs with stack dump
ailang builtins listList all 128 registered builtins
ailang docs <module>Show stdlib module documentation

Debug AST​

The ailang debug ast command shows the Core AST after ANF transformation.

Example Source​

examples/debug/anf_example.ail
module examples/debug/anf_example

-- Example showing ANF transformation
-- Run: ailang debug ast examples/debug/anf_example.ail

let add = \x y. x + y in let result = add(1)(2) in result

Running the Command​

ailang debug ast examples/debug/anf_example.ail

Output​

=== Core AST (ANF) ===
Program:
  [0] Let(add) [#16]:
    Value: Lambda([x]) [#5]:
      Body: Lambda([y]) [#4]:
        Body: Intrinsic(0) [#3]:
          Arg[0]: Var(x) [#1]
          Arg[1]: Var(y) [#2]
    Body:  Let($tmp1) [#15]:
      Value: App [#8]:
        Func: Var(add) [#6]
        Arg[0]: Lit(1) [#7]
      Body:  Let(result) [#14]:
        Value: App [#11]:
          Func: Var($tmp1) [#10]
          Arg[0]: Lit(2) [#9]
        Body:  Var(result) [#13]

Reading the Output​

  • [#N] - NodeID (keys into CoreTypeInfo)
  • Let(name) - Variable binding in ANF
  • Lambda([params]) - Function with parameter list
  • Intrinsic(0) - Primitive operation (0 = OpAdd)
  • App - Function application
  • Var(name) - Variable reference
  • Lit(value) - Literal value

Debug Compile​

The -debug-compile flag shows compilation phase timing and lowering decisions.

Example Source​

examples/debug/list_concat.ail
module examples/debug/list_concat

-- Example showing polymorphic operator lowering
-- Run: ailang check -debug-compile examples/debug/list_concat.ail

let xs = [1, 2, 3] in let ys = [4, 5, 6] in xs ++ ys

Running the Command​

ailang check -debug-compile examples/debug/list_concat.ail

Output​

→ Type checking examples/debug/list_concat.ail...
→ Effect checking...
[DEBUG] Dictionary elaboration complete for module examples/debug/list_concat
[DEBUG] Monomorphization: 0 specializations, 0 skipped
[DEBUG] Var type resolution complete
[DEBUG M-DX4] NodeID 11: type=[α9], head=List
[DEBUG] Lowering telemetry: 1 operators processed
[DEBUG]   CoreTI hits: 1 (100.0%)
[DEBUG]   CoreTI misses: 0 (0.0%)

⏱ Compilation Phase Timings:
  Loading:                0ms
  Topo Sort:              0ms
  Compile:                4ms
  Evaluate:               0ms
  ----------------------------
  Total:                  4ms

✓ No errors found!

What to Look For​

  • CoreTI hits: Percentage of operators resolved via CoreTypeInfo (should be 100%)
  • CoreTI misses: Operators that fell back to other resolution (indicates potential issues)
  • Monomorphization stats: Number of polymorphic function specializations
  • Phase timings: Where time is spent during compilation

Timeout Detection​

For compilation hangs (often caused by cyclic types), use the timeout flag:

ailang check -timeout 30s problematic_file.ail

If the timeout triggers, you'll get a stack dump showing where the compiler is stuck.

Builtin Exploration​

List All Builtins​

ailang builtins list

Shows all 128 registered builtins with their effect categories and modules.

Filter by Module​

ailang builtins list --by-module

Groups builtins by their source module (std/io, std/fs, etc.).

Filter by Effect​

ailang builtins list --by-effect

Groups builtins by their effect requirements (pure, io, fs, etc.).

Stdlib Documentation​

List Available Modules​

ailang docs --list

View Module Exports​

ailang docs std/io

Output:

# std/io
Print to stdout and read from stdin.

## Exports

  print(s: string) -> () !
    Print string without newline

  println(s: string) -> () !
    Print string with newline

  readLine() -> string !
    Read line from stdin

## Usage

  import std/io (print)
  -- or --
  import std/io as Io

Environment Variables​

Debug environment variables for detailed tracing:

VariablePurpose
DEBUG_STRICT=1Fail loudly on unhandled cases
DEBUG_MONO_VERBOSE=1Monomorphization tracing
DEBUG_OPERATOR_LOWERING=1Operator resolution details
DEBUG_PARSER=1Token position tracing
DEBUG_CODEGEN=1Record type fallback warnings

Example Usage​

DEBUG_STRICT=1 DEBUG_MONO_VERBOSE=1 ailang run examples/factorial.ail

Troubleshooting Workflow​

See Also​