minor cleanups

packages/components/src/components/SquiggleErrorAlert.tsx

@@ -22,7 +22,7 @@ const StackTrace: React.FC<Props> = ({ error }) => {
   const frames = error.getFrameArray();
   return frames.length ? (
     <div>
-      <div>Traceback:</div>
+      <div className="font-medium">Stack trace:</div>
       <div className="ml-4">
         {frames.map((frame, i) => (
           <StackTraceFrame frame={frame} key={i} />

packages/squiggle-lang/scripts/lib.mjs

@@ -36,6 +36,6 @@ export const run = (src, { output, sampleCount } = {}) => {
     "Time:",
     String(time),
     result.tag === "Error" ? red(result.tag) : green(result.tag),
-    result.tag === "Error" ? result.value.toStringWithStackTrace() : ""
+    result.tag === "Error" ? result.value.toStringWithFrameStack() : ""
   );
 };

packages/squiggle-lang/src/rescript/Reducer/Reducer_Exception.res

@@ -1,3 +0,0 @@
-// There are switch statement cases in the code which are impossible to reach by design.
-// ImpossibleException is a sign of programming error.
-exception ImpossibleException(string)

packages/squiggle-lang/src/rescript/Reducer/Reducer_FrameStack.res

@@ -1,3 +1,6 @@
+// This is called "frameStack" and not "callStack", because the last frame in errors is often not a function call.
+// A "frame" is a pair of a scope (function or top-level scope, currently stored as a string) and a location inside it.
+// See this comment to deconfuse about what a frame is: https://github.com/quantified-uncertainty/squiggle/pull/1172#issuecomment-1264115038
 type t = Reducer_T.frameStack
 
 module Frame = {
@@ -18,9 +21,6 @@ module Frame = {
 
 let make = (): t => list{}
 
-@genType
-let getTopFrame = (t: t): option<Reducer_T.frame> => Belt.List.head(t)
-
 let extend = (t: t, name: string, location: option<Reducer_Peggy_Parse.location>) =>
   t->Belt.List.add({
     name: name,

packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda.res

@@ -82,7 +82,7 @@ let doLambdaCallFrom = (
     inFunction: Some(t),
   }
 
-  SqError.rethrowWithStacktrace(() => {
+  SqError.rethrowWithFrameStack(() => {
     switch t {
     | FnLambda({body}) => body(args, newContext, reducer)
     | FnBuiltin({body}) => body(args, newContext, reducer)

packages/squiggle-lang/src/rescript/SqError.res

@@ -1,7 +1,8 @@
 type location = Reducer_Peggy_Parse.location
 
 // Messages don't contain any stack trace information.
-// FunctionRegistry functions are allowed to throw MessageExceptions, though, because they will be caught and rewrapped by Reducer_Lambda code
+// FunctionRegistry functions are allowed to throw MessageExceptions, though,
+// because they will be caught and rewrapped by Reducer_Lambda code.
 module Message = {
   @genType.opaque
   type t =
@@ -125,16 +126,16 @@ let getFrameArray = (t: t): array<Reducer_T.frame> => t.frameStack->Reducer_Fram
 @genType
 let toStringWithStackTrace = (t: t) =>
   t->toString ++ if t.frameStack->Reducer_FrameStack.isEmpty {
-      "\nTraceback:\n" ++ t.frameStack->Reducer_FrameStack.toString
+      "\nStack trace:\n" ++ t.frameStack->Reducer_FrameStack.toString
     } else {
       ""
     }
 let throw = (t: t) => t->SqException->raise
 
 let throwMessageWithFrameStack = (message: Message.t, frameStack: Reducer_FrameStack.t) =>
-  fromMessageWithFrameStack(message, frameStack)->throw
+  message->fromMessageWithFrameStack(frameStack)->throw
 
-// this shouldn't be used for most runtime errors - the resulting error would have an empty stacktrace
+// this shouldn't be used for most runtime errors - the resulting error would have an empty framestack
 let fromException = exn =>
   switch exn {
   | SqException(e) => e
@@ -143,14 +144,14 @@ let fromException = exn =>
   | _ => REOther("Unknown exception")->fromMessage
   }
 
-// converts raw exceptions into exceptions with stacktrace attached
+// converts raw exceptions into exceptions with framestack attached
 // already converted exceptions won't be affected
-let rethrowWithStacktrace = (fn: unit => 'a, frameStack: Reducer_FrameStack.t) => {
+let rethrowWithFrameStack = (fn: unit => 'a, frameStack: Reducer_FrameStack.t) => {
   try {
     fn()
   } catch {
-  | SqException(e) => e->throw // exception already has a stacktrace
-  | Message.MessageException(e) => e->throwMessageWithFrameStack(frameStack) // probably comes from FunctionRegistry, adding stacktrace
+  | SqException(e) => e->throw // exception already has a framestack
+  | Message.MessageException(e) => e->throwMessageWithFrameStack(frameStack) // probably comes from FunctionRegistry, adding framestack
   | Js.Exn.Error(obj) =>
     REJavaScriptExn(obj->Js.Exn.message, obj->Js.Exn.name)->throwMessageWithFrameStack(frameStack)
   | _ => REOther("Unknown exception")->throwMessageWithFrameStack(frameStack)