Diagnostics, Error Reporting

Fail Nodes

Potentially lots of useful information can be given with a fail node.

Comprehensive Pattern Rows

Simple pattern comprehensiveness warnings can be given, for example

(match [x]
       [1] 1)

This pattern matrix can fall through.

Might give warning:

Warning: Non-comprehensive pattern matrix

Done

Reporting on matching-so-far

If a fail node is reached, could report on how the match got to that point.

(let [x 1
      y 2
      z 3]
  (match [x y z]
         [1 3 3] 1))

Could give error:

No match found: No match for {y 3}, successful matches: {x 1, z 3}

Decent messages for Seq patterns that are gensymed will be more challenging.

Diagnostics

Some useful information to report:

• Number of branches tested at runtime (how many conds executed)
• Number of SwitchNodes created at compile time
• Number of LeafNodes created at compile time (?)
• Execution trace of Matrix->DAG compilation

Pre/post Matrix expansion

It would be useful to show the origin of the expanded occurances in error messages.

This would make following long lists easier, for example.