From 0c9973ff0363e400d3d284339b77197c40c3f60c Mon Sep 17 00:00:00 2001
From: Bruce Hill <bitbucket@bruce-hill.com>
Date: Tue, 12 Jun 2018 13:56:15 -0700
Subject: Tidying up exceptions and error reporting. Also simplified the
 grammar a tiny bit.

---
 core/control_flow.nom    | 42 ++++++++++++++++++++++++++++++------------
 core/metaprogramming.nom | 18 +++++++++++++++---
 core/scopes.nom          |  4 ++--
 3 files changed, 47 insertions(+), 17 deletions(-)

(limited to 'core')

diff --git a/core/control_flow.nom b/core/control_flow.nom
index f5c61e3..73a0f43 100644
--- a/core/control_flow.nom
+++ b/core/control_flow.nom
@@ -49,13 +49,13 @@ immediately
                 To see why this is necessary consider: (random()<.5 and false or 99)
             return
                 Lua value ".."
-                    (function()
+                    ((function()
                         if \(%condition as lua expr) then
                             return \(%when_true_expr as lua expr)
                         else
                             return \(%when_false_expr as lua expr)
                         end
-                    end)()
+                    end)())
 
 # GOTOs
 immediately
@@ -361,31 +361,46 @@ immediately
 # Try/except
 immediately
     compile [..]
-        try %action and if it succeeds %success or if it barfs %fallback
-        try %action and if it barfs %fallback or if it succeeds %success
+        try %action and if it succeeds %success or if it barfs %msg %fallback
+        try %action and if it barfs %msg %fallback or if it succeeds %success
     ..to
         Lua ".."
             do
                 local fell_through = false
-                local ok, ret = pcall(function()
+                local err, erred = nil, false
+                local ok, ret = xpcall(function()
                     \(%action as lua statements)
                     fell_through = true
+                end, function(\(%msg as lua expr))
+                    local ok, ret = pcall(function()
+                        \(%fallback as lua statements)
+                    end)
+                    if not ok then err, erred = ret, true end
                 end)
                 if ok then
                     \(%success as lua statements)
                     if not fell_through then
                         return ret
                     end
-                else
-                    \(%fallback as lua statements)
+                elseif erred then
+                    error(err, 0)
                 end
             end
+immediately
+    parse [..]
+        try %action and if it succeeds %success or if it barfs %fallback
+        try %action and if it barfs %fallback or if it succeeds %success
+    ..as: try %action and if it succeeds %success or if it barfs (=lua "") %fallback
+immediately
     parse [try %action] as
         try %action and if it succeeds: do nothing
         ..or if it barfs: do nothing
     parse [try %action and if it barfs %fallback] as
         try %action and if it succeeds: do nothing
         ..or if it barfs %fallback
+    parse [try %action and if it barfs %msg %fallback] as
+        try %action and if it succeeds: do nothing
+        ..or if it barfs %msg %fallback
     parse [try %action and if it succeeds %success] as
         try %action and if it succeeds %success or if it barfs: do nothing
 
@@ -406,17 +421,20 @@ immediately
                     fell_through = true
                 end)
                 \(%final_action as lua statements)
-                if not ok then error(ret) end
+                if not ok then error(ret, 0) end
                 if not fell_through then return ret end
             end
 
 # Inline thunk:
 immediately
     compile [result of %body] to
-        Lua value ".."
-            (function()
-                \(%body as lua statements)
-            end)()
+        %body <- (%body as lua statements)
+        declare locals in %body
+        return
+            Lua value ".."
+                ((function()
+                    \%body
+                end)())
 
 # Coroutines:
 immediately
diff --git a/core/metaprogramming.nom b/core/metaprogramming.nom
index 8ad9448..83293c1 100644
--- a/core/metaprogramming.nom
+++ b/core/metaprogramming.nom
@@ -132,15 +132,25 @@ immediately
         lua> ".."
             local lua = nomsu:tree_to_lua(\%tree)
             if not lua.is_value then
-                error("Invalid thing to convert to lua expr: "..tostring(\%tree))
+                compile_error(\%tree, "Invalid thing to convert to lua expr:\n%s")
             end
             return lua
 
     action [%tree as lua statements]
         =lua "nomsu:tree_to_lua(\%tree):as_statements()"
+
+    action [%tree as lua return]
+        =lua "nomsu:tree_to_lua(\%tree):as_statements('return ')"
     
-    action [%tree with vars %vars]
-        =lua "\%tree:map(\%vars)"
+immediately
+    compile [%tree with vars %vars] to
+        barf "Deprecated"
+
+    compile [%tree with %t -> %replacement] to
+        Lua value ".."
+            \(%tree as lua expr):map(function(\(%t as lua expr))
+                \(%replacement as lua return)
+            end)
     
     compile [declare locals in %code] to
         Lua value "\(%code as lua expr):declare_locals()"
@@ -202,6 +212,8 @@ immediately
 
 # Error functions
 immediately
+    compile [traceback] to: Lua value "debug.traceback()"
+    compile [traceback %] to: Lua value "debug.traceback('', \(% as lua expr))"
     compile [barf] to: Lua "error(nil, 0);"
     compile [barf %msg] to: Lua "error(\(%msg as lua expr), 0);"
     compile [assume %condition] to
diff --git a/core/scopes.nom b/core/scopes.nom
index 72631c0..02ad73d 100644
--- a/core/scopes.nom
+++ b/core/scopes.nom
@@ -30,7 +30,7 @@ compile [using %definitions %body, using %definitions do %body] to
                 \%setup_lua
                 if not ok then
                     ACTIONS, COMPILE_ACTIONS, ARG_ORDERS = old_actions, old_compile_actions, old_arg_orders
-                    error(ret)
+                    error(ret, 0)
                 end
                 if not fell_through then
                     ACTIONS, COMPILE_ACTIONS, ARG_ORDERS = old_actions, old_compile_actions, old_arg_orders
@@ -42,7 +42,7 @@ compile [using %definitions %body, using %definitions do %body] to
                 \%body_lua
                 ACTIONS, COMPILE_ACTIONS, ARG_ORDERS = old_actions, old_compile_actions, old_arg_orders
                 if not ok then
-                    error(ret)
+                    error(ret, 0)
                 end
                 if not fell_through then
                     return ret
-- 
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