language Error tracking

Close #3

14 files changed, 125 insertions, 31 deletions

diff --git a/copilot.moon b/copilot.moon
index a196d9b..600d2ed 100644
--- a/copilot.moon
+++ b/copilot.moon
@@ -1,5 +1,5 @@
 lfs = require 'lfs'
-import parse, globals, Scope, Registry from require 'core'
+import parse, globals, Scope, Error, Registry from require 'core'
 
 slurp = (file) ->
   file = io.open file, 'r'
@@ -40,8 +40,9 @@ class Copilot
       return
 
     scope = Scope globals
-    root = L\try "error evaluating:", ast\eval, scope, @registry
-    if not root
+    ok, root = Error.try "evaluating '#{@file}'", ast\eval, scope, @registry
+    if not ok
+      print root
       @registry\rollback_eval!
       return
 
diff --git a/core/base/init.moon b/core/base/init.moon
index 64b34f4..bb35140 100644
--- a/core/base/init.moon
+++ b/core/base/init.moon
@@ -12,6 +12,7 @@
 -- @see match
 -- @see Value
 -- @see Result
+-- @see Error
 
 import IO from require 'core.base.io'
 import Op from require 'core.base.op'
@@ -21,6 +22,7 @@ import Input from require 'core.base.input'
 import match from require 'core.base.match'
 import Value from require 'core.value'
 import Result from require 'core.result'
+import Error from require 'core.error'
 
 {
   :IO
@@ -31,5 +33,5 @@ import Result from require 'core.result'
   :match
 
   -- redundant exports, to keep anything an extension might need in one import
-  :Value, :Result
+  :Value, :Result, :Error
 }
diff --git a/core/base/match.moon b/core/base/match.moon
index a20bcdc..cb82ac4 100644
--- a/core/base/match.moon
+++ b/core/base/match.moon
@@ -2,6 +2,7 @@
 -- Utilities for matching `Result` types.
 --
 -- @module match
+import Error from require 'core.error'
 unpack or= table.unpack
 
 class Pattern
@@ -39,11 +40,11 @@ class Pattern
       matched = while @matches results[1]
         table.remove results, 1
 
-      assert @opt or #matched > 0, "expected at least one argument for spread"
+      assert @opt or #matched > 0, Error 'argument', "expected at least one argument for spread"
       matched
     else
       matches = @matches results[1]
-      assert @opt or matches, "couldn't match argument #{results[1]} as #{@}"
+      assert @opt or matches, Error 'argument', "argument #{results[1].value} incompatible with expected type #{@}"
       if matches then table.remove results, 1
 
   __tostring: =>
@@ -84,7 +85,7 @@ match = (pattern, inputs) ->
     pattern = rest
     Pattern pat
   values = [p\match inputs for p in *patterns]
-  assert #inputs == 0, "#{#inputs} extra arguments given!"
+  assert #inputs == 0, Error 'argument', "#{#inputs} extra arguments given!"
   values
 
 {
diff --git a/core/error.moon b/core/error.moon
new file mode 100644
index 0000000..a06c359
--- /dev/null
+++ b/core/error.moon
@@ -0,0 +1,85 @@
+----
+-- Language error and traceback.
+--
+-- @classmod Error
+class Error
+--- members
+-- @section members
+
+  --- append a traceback frame.
+  --
+  -- `where` should denote where the Error occured and fit grammatically to
+  -- complete the sentence `"{error} occured while {where}"`
+  --
+  -- @tparam string where
+  add_frame: (where) => @trace ..= "\n  while #{where}"
+
+  __tostring: => "#{@kind} error: #{@message}#{@detail}#{@trace}"
+
+--- static functions
+-- @section static
+
+  --- create a new Error.
+  --
+  -- `kind` should be one of:
+  --
+  -- - `'reference'`: error concerning symbol resolution
+  -- - `'argument'`: error concerning Op argument matching
+  -- - `'implementation'`: error in the Lua/MoonScript implementation of alive.
+  --   Should not occur in normal operation, and constitutes a bug.
+  --
+  -- @classmethod
+  -- @tparam string kind
+  -- @tparam string message
+  -- @tparam ?string detail
+  new: (@kind, @message, @detail) =>
+    @trace = ""
+
+  handler = (err) ->
+    if err.__class == Error
+      err
+    else
+      Error 'implementation', err, debug.traceback 'Lua error below:', 2
+  --- Wrap function errors in a traceback frame.
+  --
+  -- Execute `fn(...)`, and turn any error thrown as a result into an
+  -- `Error` instance, before re-throwing it.
+  --
+  -- When `Error` instances are caught, `frame` is added to the traceback.
+  -- All other error values are turned into `'implementation'` Errors.
+  --
+  -- @tparam string frame
+  -- @tparam function fn
+  @wrap: (frame, fn, ...) ->
+    results = { xpcall fn, handler, ... }
+    ok = table.remove results, 1
+    if ok
+      unpack results
+    else
+      error with results[1]
+        \add_frame frame
+
+  --- Capture and wrap function errors in traceback frame.
+  --
+  -- Execute `fn(...)`, and turn any error thrown as a result into an
+  -- `Error` instance, before re-throwing it.
+  --
+  -- When `Error` instances are caught, `frame` is added to the traceback.
+  -- All other error values are turned into `'implementation'` Errors.
+  --
+  -- @tparam string frame
+  -- @tparam function fn
+  -- @treturn boolean `ok` true if exeuction suceeded without errors
+  -- @treturn Error|any `error_or_results` the `Error` instance or results
+  @try: (frame, fn, ...) ->
+    results = { xpcall fn, handler, ... }
+    ok = table.remove results, 1
+    if ok
+      ok, unpack results
+    else
+      ok, with results[1]
+        \add_frame frame
+
+{
+  :Error
+}
diff --git a/core/init.moon b/core/init.moon
index a5e892d..00e3cd4 100644
--- a/core/init.moon
+++ b/core/init.moon
@@ -17,6 +17,7 @@ L or= setmetatable {}, __index: => ->
 import Value from require 'core.value'
 import Result from require 'core.result'
 import Scope from require 'core.scope'
+import Error from require 'core.error'
 import Registry, SimpleRegistry from require 'core.registry'
 import Tag from require 'core.tag'
 
@@ -35,6 +36,7 @@ globals = Scope.from_table require 'core.builtin'
 -- @tfield Cell Cell
 -- @tfield RootCell RootCell
 -- @tfield Scope Scope
+-- @tfield Error Error
 -- @tfield Registry Registry
 -- @tfield Tag Tag
 -- @tfield Scope globals global definitons
@@ -42,7 +44,7 @@ globals = Scope.from_table require 'core.builtin'
 {
   :Value, :Result
   :Cell, :RootCell
-  :Scope
+  :Scope, :Error
 
   :Registry, :SimpleRegistry, :Tag
 
diff --git a/core/invoke.moon b/core/invoke.moon
index 736f284..97d3949 100644
--- a/core/invoke.moon
+++ b/core/invoke.moon
@@ -6,6 +6,7 @@ import Value from require 'core.value'
 import Result from require 'core.result'
 import Action from require 'core.base'
 import Scope from require 'core.scope'
+import Error from require 'core.error'
 
 --- `Action` implementation that invokes an `Op`.
 --
@@ -40,7 +41,7 @@ class op_invoke extends Action
   -- @treturn Result
   eval: (scope, tail) =>
     children = [L\push expr\eval, scope for expr in *tail]
-    @op\setup [result for result in *children], scope
+    Error.wrap "invoking #{@op}#{@tag}", @op\setup, [result for result in *children], scope
 
     any_dirty = false
     for input in @op\all_inputs!
@@ -91,8 +92,8 @@ class fn_invoke extends Action
       with L\push tail[i]\eval, outer_scope
         fn_scope\set name, \make_ref!
 
-    body = body\clone @tag
-    result = body\eval fn_scope
+    clone = body\clone @tag
+    result = Error.wrap "invoking function #{body.tag} at #{@tag}", clone\eval, fn_scope
 
     table.insert children, result
     Result :children, value: result.value
diff --git a/core/value.moon b/core/value.moon
index bda6127..7f5a93d 100644
--- a/core/value.moon
+++ b/core/value.moon
@@ -3,6 +3,7 @@
 --
 -- @classmod Value
 import Result from require 'core.result'
+import Error from require 'core.error'
 import scope, base, registry from require 'core.cycle'
 
 ancestor = (klass) ->
@@ -107,7 +108,7 @@ class Value
       when 'num', 'str'
         Result value: @
       when 'sym'
-        assert (scope\get @value), "undefined reference to symbol '#{@value}'"
+        assert (scope\get @value), Error 'reference', "undefined symbol '#{@value}'"
       else
         error "cannot evaluate #{@}"
 
diff --git a/core/version.moon b/core/version.moon
index e5a965c..af97600 100644
--- a/core/version.moon
+++ b/core/version.moon
@@ -12,8 +12,8 @@
 -- @tfield string web the repo web URL
 {
   tag: "v0.0"
-  rev_short: "23f893a"
-  rev_long: "23f893a1303b35e11d7103d892c40b7e8d209a06"
+  rev_short: "662def4"
+  rev_long: "662def4ef082412147ae8126e80065d245f4b426"
   repo: "https://github.com/s-ol/alivecoding.git"
   web: "https://github.com/s-ol/alivecoding/tree/v0.0"
 }
diff --git a/lib/logic.moon b/lib/logic.moon
index 7cf8695..7264be0 100644
--- a/lib/logic.moon
+++ b/lib/logic.moon
@@ -1,4 +1,4 @@
-import Op, Input, match from require 'core.base'
+import Op, Input, Error, match from require 'core.base'
 
 all_same = (first, list) ->
   for v in *list
@@ -72,7 +72,7 @@ class not_eq extends Op
   new: => super 'bool'
 
   setup: (inputs) =>
-    assert #inputs > 1, "neq need at least two values"
+    assert #inputs > 1, Error 'argument', "need at least two values"
     super [Input.value v for v in *inputs]
 
   tick: =>
diff --git a/lib/math.moon b/lib/math.moon
index 02ba1e1..84e6682 100644
--- a/lib/math.moon
+++ b/lib/math.moon
@@ -1,4 +1,4 @@
-import Op, Value, Input, match from require 'core.base'
+import Op, Value, Error, Input, match from require 'core.base'
 unpack or= table.unpack
 
 class ReduceOp extends Op
@@ -71,7 +71,9 @@ func_op = (name, arity, func) ->
 
     setup: (inputs) =>
       { params } = match '*num', inputs
-      assert #params == arity, "#{@} needs exactly #{arity} parameters" if arity != '*'
+      if arity != '*'
+        err = Error 'argument', "need exactly #{arity} arguments"
+        assert #params == arity, err
       super [Input.value p for p in *params]
 
     tick: => @out\set func unpack @unwrap_all!
diff --git a/lib/midi/core.moon b/lib/midi/core.moon
index 8378b1d..75defdf 100644
--- a/lib/midi/core.moon
+++ b/lib/midi/core.moon
@@ -1,4 +1,4 @@
-import IO, Op, Registry, Input, match from require 'core.base'
+import IO, Op, Registry, Input, Error, match from require 'core.base'
 import RtMidiIn, RtMidiOut, RtMidi from require 'luartmidi'
 import band, bor, lshift, rshift from require 'bit32'
 
@@ -49,7 +49,7 @@ class MidiPort extends IO
         coroutine.yield msg
 
   send: (status, chan, a, b) =>
-    assert @out, "#{@} is not an output or bidirectional port"
+    assert @out, Error 'type', "#{@} is not an output or bidirectional port"
     if 'string' == type 'status'
       status = bor (lshift rMIDI[status], 4), chan
     @out\sendmessage status, a, b
diff --git a/lib/pilot.moon b/lib/pilot.moon
index f24270e..a687e48 100644
--- a/lib/pilot.moon
+++ b/lib/pilot.moon
@@ -1,4 +1,4 @@
-import Op, Input, match from require 'core.base'
+import Op, Input, Error, match from require 'core.base'
 import udp from require 'socket'
 
 local conn
@@ -25,7 +25,7 @@ class play extends Op
 
   setup: (inputs) =>
     { trig, args } = match 'bang *any', inputs
-    assert #args < 6, "too many arguments!"
+    assert #args < 6, Error 'argument', "too many arguments!"
     super
       trig: Input.event trig
       args: [Input.cold a for a in *args]
@@ -40,7 +40,7 @@ class play_ extends Op
 
   setup: (inputs) =>
     { chan, octv, note, args } = match 'any any any *any', inputs
-    assert #args < 3, "too many arguments!"
+    assert #args < 3, Error 'argument', "too many arguments!"
     super
       chan: Input.cold chan
       octv: Input.cold octv
diff --git a/lib/sc.moon b/lib/sc.moon
index ebdcd3b..7562620 100644
--- a/lib/sc.moon
+++ b/lib/sc.moon
@@ -1,4 +1,4 @@
-import Op, Input, match from require 'core.base'
+import Op, Input, Error, match from require 'core.base'
 import pack from require 'osc'
 import dns, udp from require 'socket'
 
@@ -8,11 +8,11 @@ class play extends Op
   setup: (inputs) =>
     { socket, synth, trig, ctrls } = match 'udp/socket str bang *any?', inputs
 
-    assert #ctrls % 2 == 0, "parameters need to be specified as pairs"
+    assert #ctrls % 2 == 0, Error 'argument', "parameters need to be specified as pairs"
     for key in *ctrls[1,,2]
-      assert key\type! == 'str', "ony strings are supported as control names"
+      assert key\type! == 'str', Error 'argument', "ony strings are supported as control names"
     for val in *ctrls[2,,2]
-      assert val\type! == 'num', "only numbers are supported as control values"
+      assert val\type! == 'num', Error 'argument', "only numbers are supported as control values"
 
     super
       trig:   Input.event trig
diff --git a/lib/util.moon b/lib/util.moon
index 1fddca4..f816eee 100644
--- a/lib/util.moon
+++ b/lib/util.moon
@@ -1,5 +1,4 @@
-import Op, Value, Input, match
-  from require 'core.base'
+import Op, Value, Input, Error, match from require 'core.base'
 
 all_same = (list) ->
   for v in *list[2,]
@@ -19,7 +18,7 @@ when i is a num, it is (floor)ed and the matching argument (starting from 0) is
     { i, values } = match 'any *any', inputs
 
     i_type = i\type!
-    assert i_type == 'bool' or i_type == 'num', "#{@}: i has to be bool or num"
+    assert i_type == 'bool' or i_type == 'num', Error 'argument', "i has to be bool or num"
     typ = all_same [v\type! for v in *values]
     @out = Value typ if not @out or typ != @out.type
 
@@ -50,7 +49,7 @@ when i is a num, it is (floor)ed and the matching argument (starting from 0) is
     { i, values } = match 'any *any', inputs
 
     i_type = i\type!
-    assert i_type == 'bool' or i_type == 'num', "#{@}: i has to be bool or num"
+    assert i_type == 'bool' or i_type == 'num', Error 'argument', "i has to be bool or num"
     typ = all_same [v\type! for v in *values]
     @out = Value typ if not @out or typ != @out.type