From 26dbd29ec8eecf495f2576e6f6266713d2059279 Mon Sep 17 00:00:00 2001
From: Vyacheslav Matyukhin <me@berekuk.ru>
Date: Wed, 5 Oct 2022 04:51:23 +0400
Subject: [PATCH] framestack reimplemented

---
 .../src/components/SquiggleErrorAlert.tsx     | 20 ++++----
 packages/components/src/lib/utility.ts        |  2 +-
 packages/squiggle-lang/src/js/SqError.ts      | 33 +++++++++----
 .../squiggle-lang/src/js/SqValueLocation.ts   |  1 -
 packages/squiggle-lang/src/js/index.ts        |  2 +-
 .../src/rescript/Reducer/Reducer_Context.res  |  7 ++-
 .../Reducer_Expression/Reducer_Expression.res | 22 ++++++---
 .../Reducer_Expression_ExpressionBuilder.res  |  9 ++--
 .../Reducer_Expression_T.res                  |  2 +-
 .../rescript/Reducer/Reducer_FrameStack.res   | 42 +++++++++--------
 .../src/rescript/Reducer/Reducer_Lambda.res   | 25 ++++++++--
 .../src/rescript/Reducer/Reducer_Lambda_T.res |  8 ++++
 .../Reducer_Peggy_GeneratedParser.peggy       |  6 +--
 .../Reducer_Peggy/Reducer_Peggy_Parse.res     |  2 +-
 .../Reducer_Peggy_ToExpression.res            |  2 +-
 .../rescript/Reducer/Reducer_Peggy/helpers.ts |  6 ++-
 .../src/rescript/Reducer/Reducer_T.res        | 10 ++--
 .../squiggle-lang/src/rescript/SqError.res    | 46 +++++++++----------
 18 files changed, 153 insertions(+), 92 deletions(-)
 create mode 100644 packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda_T.res

diff --git a/packages/components/src/components/SquiggleErrorAlert.tsx b/packages/components/src/components/SquiggleErrorAlert.tsx
index fb4721eb..c4b14f17 100644
--- a/packages/components/src/components/SquiggleErrorAlert.tsx
+++ b/packages/components/src/components/SquiggleErrorAlert.tsx
@@ -1,4 +1,4 @@
-import { SqError, SqLocation } from "@quri/squiggle-lang";
+import { SqError, SqFrame } from "@quri/squiggle-lang";
 import React from "react";
 import { ErrorAlert } from "./Alert";
 
@@ -6,24 +6,26 @@ type Props = {
   error: SqError;
 };
 
-const StackTraceLocation: React.FC<{ location: SqLocation }> = ({
-  location,
-}) => {
+const StackTraceFrame: React.FC<{ frame: SqFrame }> = ({ frame }) => {
+  const location = frame.location();
   return (
     <div>
-      Line {location.start.line}, column {location.start.column}
+      {frame.name()}
+      {location
+        ? ` at line ${location.start.line}, column ${location.start.column}`
+        : ""}
     </div>
   );
 };
 
 const StackTrace: React.FC<Props> = ({ error }) => {
-  const locations = error.toLocationArray();
-  return locations.length ? (
+  const frames = error.getFrameArray();
+  return frames.length ? (
     <div>
       <div>Traceback:</div>
       <div className="ml-4">
-        {locations.map((location, i) => (
-          <StackTraceLocation location={location} key={i} />
+        {frames.map((frame, i) => (
+          <StackTraceFrame frame={frame} key={i} />
         ))}
       </div>
     </div>
diff --git a/packages/components/src/lib/utility.ts b/packages/components/src/lib/utility.ts
index c3ce08a4..cb002954 100644
--- a/packages/components/src/lib/utility.ts
+++ b/packages/components/src/lib/utility.ts
@@ -45,7 +45,7 @@ export function getValueToRender({ result, bindings }: ResultAndBindings) {
 
 export function getErrorLocations(result: ResultAndBindings["result"]) {
   if (result.tag === "Error") {
-    const location = result.value.toLocation();
+    const location = result.value.location();
     return location ? [location] : [];
   } else {
     return [];
diff --git a/packages/squiggle-lang/src/js/SqError.ts b/packages/squiggle-lang/src/js/SqError.ts
index 61d09096..59036830 100644
--- a/packages/squiggle-lang/src/js/SqError.ts
+++ b/packages/squiggle-lang/src/js/SqError.ts
@@ -1,8 +1,9 @@
 import * as RSError from "../rescript/SqError.gen";
+import * as RSReducerT from "../rescript/Reducer/Reducer_T.gen";
 
-import * as RSCallStack from "../rescript/Reducer/Reducer_CallStack.gen";
+import * as RSFrameStack from "../rescript/Reducer/Reducer_FrameStack.gen";
 
-export type SqFrame = RSCallStack.frame;
+export { location as SqLocation } from "../rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.gen";
 
 export class SqError {
   constructor(private _value: RSError.t) {}
@@ -19,17 +20,31 @@ export class SqError {
     return new SqError(RSError.createOtherError(v));
   }
 
-  getTopFrame(): SqCallFrame | undefined {
-    const frame = RSCallStack.getTopFrame(RSError.getStackTrace(this._value));
-    return frame ? new SqCallFrame(frame) : undefined;
+  getTopFrame(): SqFrame | undefined {
+    const frame = RSFrameStack.getTopFrame(RSError.getFrameStack(this._value));
+    return frame ? new SqFrame(frame) : undefined;
   }
 
-  getFrameArray(): SqCallFrame[] {
+  getFrameArray(): SqFrame[] {
     const frames = RSError.getFrameArray(this._value);
-    return frames.map((frame) => new SqCallFrame(frame));
+    return frames.map((frame) => new SqFrame(frame));
+  }
+
+  location() {
+    return this.getTopFrame()?.location();
   }
 }
 
-export class SqCallFrame {
-  constructor(private _value: SqFrame) {}
+export class SqFrame {
+  constructor(private _value: RSReducerT.frame) {}
+
+  name(): string {
+    return RSFrameStack.Frame.toName(this._value);
+  }
+
+  location() {
+    console.log(RSFrameStack);
+    console.log(RSFrameStack.Frame);
+    return RSFrameStack.Frame.toLocation(this._value);
+  }
 }
diff --git a/packages/squiggle-lang/src/js/SqValueLocation.ts b/packages/squiggle-lang/src/js/SqValueLocation.ts
index 33c7060b..ad2e7e02 100644
--- a/packages/squiggle-lang/src/js/SqValueLocation.ts
+++ b/packages/squiggle-lang/src/js/SqValueLocation.ts
@@ -1,4 +1,3 @@
-import { isParenthesisNode } from "mathjs";
 import { SqProject } from "./SqProject";
 
 type PathItem = string | number;
diff --git a/packages/squiggle-lang/src/js/index.ts b/packages/squiggle-lang/src/js/index.ts
index aac26bd5..886c830a 100644
--- a/packages/squiggle-lang/src/js/index.ts
+++ b/packages/squiggle-lang/src/js/index.ts
@@ -13,7 +13,7 @@ export {
   environment,
   defaultEnvironment,
 } from "../rescript/ForTS/ForTS_Distribution/ForTS_Distribution.gen";
-export { SqError } from "./SqError";
+export { SqError, SqFrame, SqLocation } from "./SqError";
 export { SqShape } from "./SqPointSetDist";
 
 export { resultMap } from "./types";
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Context.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Context.res
index af596dc2..a2d98f92 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Context.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Context.res
@@ -4,8 +4,13 @@ let defaultEnvironment: Reducer_T.environment = DistributionOperation.defaultEnv
 
 let createContext = (stdLib: Reducer_Namespace.t, environment: Reducer_T.environment): t => {
   {
-    callStack: list{},
+    frameStack: list{},
     bindings: stdLib->Reducer_Bindings.fromNamespace->Reducer_Bindings.extend,
     environment: environment,
+    inFunction: None,
   }
 }
+
+let currentFunctionName = (t: t): string => {
+  t.inFunction->E.O2.fmap(Reducer_Lambda_T.name)->E.O2.default("<top>")
+}
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
index f334335a..0036816b 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
@@ -2,14 +2,16 @@ module Bindings = Reducer_Bindings
 module Result = Belt.Result
 module T = Reducer_T
 
-let toLocation = (expression: T.expression): SqError.location => {
+let toLocation = (expression: T.expression): Reducer_Peggy_Parse.location => {
   expression.ast.location
 }
 
 let throwFrom = (error: SqError.Message.t, expression: T.expression, context: T.context) =>
-  error->SqError.throwMessage(
-    context.callStack,
-    location: Some(expression->toLocation)
+  error->SqError.throwMessageWithFrameStack(
+    context.frameStack->Reducer_FrameStack.extend(
+      context->Reducer_Context.currentFunctionName,
+      Some(expression->toLocation),
+    ),
   )
 
 /*
@@ -93,9 +95,9 @@ let rec evaluate: T.reducerFn = (expression, context): (T.value, T.context) => {
       }
     }
 
-  | T.ELambda(parameters, body) => (
+  | T.ELambda(parameters, body, name) => (
       Reducer_Lambda.makeLambda(
-        None, // TODO - pass function name from parser
+        name,
         parameters,
         context.bindings,
         body,
@@ -112,7 +114,13 @@ let rec evaluate: T.reducerFn = (expression, context): (T.value, T.context) => {
       })
       switch lambda {
       | T.IEvLambda(lambda) => {
-          let result = Reducer_Lambda.doLambdaCall(lambda, argValues, context, evaluate)
+          let result = Reducer_Lambda.doLambdaCallFrom(
+            lambda,
+            argValues,
+            context,
+            evaluate,
+            Some(expression->toLocation), // we have to pass the location of a current expression here, to put it on frameStack
+          )
           (result, context)
         }
       | _ => RENotAFunction(lambda->Reducer_Value.toString)->throwFrom(expression, context)
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res
index 965fc499..527331fb 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_ExpressionBuilder.res
@@ -9,10 +9,11 @@ let eBool = aBool => aBool->T.IEvBool->T.EValue
 
 let eCall = (fn: expression, args: array<expression>): expressionContent => T.ECall(fn, args)
 
-let eLambda = (parameters: array<string>, expr: expression): expressionContent => T.ELambda(
-  parameters,
-  expr,
-)
+let eLambda = (
+  parameters: array<string>,
+  expr: expression,
+  name: option<string>,
+): expressionContent => T.ELambda(parameters, expr, name)
 
 let eNumber = aNumber => aNumber->T.IEvNumber->T.EValue
 
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res
index 6b2982f6..c7804c7a 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression_T.res
@@ -24,7 +24,7 @@ let rec toString = (expression: t) =>
     `${predicate->toString} ? (${trueCase->toString}) : (${falseCase->toString})`
   | EAssign(name, value) => `${name} = ${value->toString}`
   | ECall(fn, args) => `(${fn->toString})(${args->Js.Array2.map(toString)->commaJoin})`
-  | ELambda(parameters, body) => `{|${parameters->commaJoin}| ${body->toString}}`
+  | ELambda(parameters, body, _) => `{|${parameters->commaJoin}| ${body->toString}}`
   | EValue(aValue) => Reducer_Value.toString(aValue)
   }
 
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_FrameStack.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_FrameStack.res
index 217993f0..e61efd5d 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_FrameStack.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_FrameStack.res
@@ -1,37 +1,43 @@
 type t = Reducer_T.frameStack
 
 module Frame = {
-  let toString = ({lambda, location}: Reducer_T.frame) =>
-    `${fromFrame} at ${location.start.line->Js.Int.toString}, column ${location.start.column->Js.Int.toString}`
+  let toString = ({name, location}: Reducer_T.frame) =>
+    name ++
+    switch location {
+    | Some(location) =>
+      ` at line ${location.start.line->Js.Int.toString}, column ${location.start.column->Js.Int.toString}`
+    | None => ""
+    }
+
+  @genType
+  let toLocation = (t: Reducer_T.frame): option<Reducer_Peggy_Parse.location> => t.location
+
+  @genType
+  let toName = (t: Reducer_T.frame): string => t.name
 }
 
 let make = (): t => list{}
 
-let topFrameName = (t: t) =>
-  switch t->getTopFrame {
-  | Some({lambda}) =>
-    switch lambda {
-    | FnLambda({name}) => name
-    | FnBuiltin({name}) => name
-    }
-  | None => "<main>"
-  }
+@genType
+let getTopFrame = (t: t): option<Reducer_T.frame> => Belt.List.head(t)
 
-let extend = (t: t, lambda: Reducer_T.lambdaValue, location: option<location>) =>
+let extend = (t: t, name: string, location: option<Reducer_Peggy_Parse.location>) =>
   t->Belt.List.add({
-    lambda: lambda,
-    fromLocation: location,
-    fromFrame: t->topFrameName,
+    name: name,
+    location: location,
   })
 
 let toString = (t: t) =>
-  t->Belt.List.map(s => "  " ++ s->toStringFrame ++ "\n")->Belt.List.toArray->Js.Array2.joinWith("")
+  t
+  ->Belt.List.map(s => "  " ++ s->Frame.toString ++ "\n")
+  ->Belt.List.toArray
+  ->Js.Array2.joinWith("")
 
 @genType
-let toFrameArray = (t: t): array<frame> => t->Belt.List.toArray
+let toFrameArray = (t: t): array<Reducer_T.frame> => t->Belt.List.toArray
 
 @genType
-let getTopFrame = (t: t): option<frame> => t->Belt.List.head
+let getTopFrame = (t: t): option<Reducer_T.frame> => t->Belt.List.head
 
 let isEmpty = (t: t): bool =>
   switch t->Belt.List.head {
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda.res
index 04adeea0..98a272db 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda.res
@@ -33,7 +33,8 @@ let makeLambda = (
     let lambdaContext: Reducer_T.context = {
       bindings: localBindingsWithParameters, // based on bindings at the moment of lambda creation
       environment: context.environment, // environment at the moment when lambda is called
-      callStack: context.callStack, // extended by main `evaluate` function
+      frameStack: context.frameStack, // already extended in `doLambdaCall`
+      inFunction: context.inFunction, // already updated in `doLambdaCall`
     }
 
     let (value, _) = reducer(body, lambdaContext)
@@ -49,7 +50,7 @@ let makeLambda = (
   })
 }
 
-// stdlib lambdas (everything in FunctionRegistry) is built by this method. Body is generated in SquiggleLibrary_StdLib.res
+// stdlib functions (everything in FunctionRegistry) are built by this method. Body is generated in SquiggleLibrary_StdLib.res
 let makeFFILambda = (name: string, body: Reducer_T.lambdaBody): t => FnBuiltin({
   // Note: current bindings could be accidentally exposed here through context (compare with native lambda implementation above, where we override them with local bindings).
   // But FunctionRegistry API is too limited for that to matter. Please take care not to violate that in the future by accident.
@@ -65,10 +66,20 @@ let parameters = (t: t): array<string> => {
   }
 }
 
-let doLambdaCall = (t: t, args, context: Reducer_Context.t, reducer) => {
+let doLambdaCallFrom = (
+  t: t,
+  args: array<Reducer_T.value>,
+  context: Reducer_T.context,
+  reducer,
+  location: option<Reducer_Peggy_Parse.location>,
+) => {
   let newContext = {
     ...context,
-    callStack: t->Reducer_CallStack.extend(t),
+    frameStack: context.frameStack->Reducer_FrameStack.extend(
+      context->Reducer_Context.currentFunctionName,
+      location,
+    ),
+    inFunction: Some(t),
   }
 
   SqError.rethrowWithStacktrace(() => {
@@ -76,5 +87,9 @@ let doLambdaCall = (t: t, args, context: Reducer_Context.t, reducer) => {
     | FnLambda({body}) => body(args, newContext, reducer)
     | FnBuiltin({body}) => body(args, newContext, reducer)
     }
-  }, newContext.callStack)
+  }, newContext.frameStack)
+}
+
+let doLambdaCall = (t: t, args, context, reducer) => {
+  doLambdaCallFrom(t, args, context, reducer, None)
 }
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda_T.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda_T.res
new file mode 100644
index 00000000..ab0724b4
--- /dev/null
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Lambda_T.res
@@ -0,0 +1,8 @@
+type t = Reducer_T.lambdaValue
+
+let name = (t: t): string => {
+  switch t {
+  | FnLambda({name}) => name->E.O2.default("<anonymous>")
+  | FnBuiltin({name}) => name
+  }
+}
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_GeneratedParser.peggy b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_GeneratedParser.peggy
index 0cd28a86..cbe1f9da 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_GeneratedParser.peggy
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_GeneratedParser.peggy
@@ -50,7 +50,7 @@ letStatement
 
 defunStatement
   = variable:variable '(' _nl args:array_parameters _nl ')' _ assignmentOp _nl body:innerBlockOrExpression
-    { var value = h.nodeLambda(args, body, location())
+    { var value = h.nodeLambda(args, body, location(), variable)
       return h.nodeLetStatement(variable, value, location()) }
 
   assignmentOp "assignment" = '='
@@ -261,9 +261,9 @@ valueConstructor
 lambda  
   = '{' _nl '|' _nl args:array_parameters _nl '|' _nl statements:array_statements  finalExpression: (statementSeparator @expression)  _nl '}'
       { statements.push(finalExpression) 
-        return h.nodeLambda(args, h.nodeBlock(statements, location()), location()) }
+        return h.nodeLambda(args, h.nodeBlock(statements, location()), location(), undefined) }
   / '{' _nl '|' _nl args:array_parameters _nl '|' _nl finalExpression: expression  _nl '}'
-      { return h.nodeLambda(args, finalExpression, location()) }
+      { return h.nodeLambda(args, finalExpression, location(), undefined) }
 
 arrayConstructor 'array'
   = '[' _nl ']'
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res
index b2b57bed..001f3e5b 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res
@@ -44,7 +44,7 @@ type nodeIdentifier = {...node, "value": string}
 type nodeInteger = {...node, "value": int}
 type nodeKeyValue = {...node, "key": node, "value": node}
 type nodeRecord = {...node, "elements": array<nodeKeyValue>}
-type nodeLambda = {...node, "args": array<nodeIdentifier>, "body": node}
+type nodeLambda = {...node, "args": array<nodeIdentifier>, "body": node, "name": option<string>}
 type nodeLetStatement = {...node, "variable": nodeIdentifier, "value": node}
 type nodeModuleIdentifier = {...node, "value": string}
 type nodeString = {...node, "value": string}
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression.res
index 6c187476..2e858c55 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_ToExpression.res
@@ -20,7 +20,7 @@ let rec fromNode = (node: Parse.node): expression => {
         nodeLambda["args"]->Js.Array2.map((argNode: Parse.nodeIdentifier) => argNode["value"])
       let body = nodeLambda["body"]->fromNode
 
-      ExpressionBuilder.eLambda(args, body)
+      ExpressionBuilder.eLambda(args, body, nodeLambda["name"])
     }
 
     let caseRecord = (nodeRecord): expressionContent => {
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/helpers.ts b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/helpers.ts
index 6e9fe80c..6253b875 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/helpers.ts
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/helpers.ts
@@ -89,6 +89,7 @@ type NodeLambda = Node & {
   type: "Lambda";
   args: AnyPeggyNode[];
   body: AnyPeggyNode;
+  name?: string;
 };
 
 type NodeTernary = Node & {
@@ -217,9 +218,10 @@ export function nodeKeyValue(
 export function nodeLambda(
   args: AnyPeggyNode[],
   body: AnyPeggyNode,
-  location: LocationRange
+  location: LocationRange,
+  name?: NodeIdentifier
 ): NodeLambda {
-  return { type: "Lambda", args, body, location };
+  return { type: "Lambda", args, body, location, name: name?.value };
 }
 export function nodeLetStatement(
   variable: NodeIdentifier,
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_T.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_T.res
index eab7bd55..dcc9e4bf 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_T.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_T.res
@@ -36,7 +36,7 @@ and expressionContent =
   | ETernary(expression, expression, expression)
   | EAssign(string, expression)
   | ECall(expression, array<expression>)
-  | ELambda(array<string>, expression)
+  | ELambda(array<string>, expression, option<string>)
   | EValue(value)
 
 and expression = {
@@ -50,18 +50,18 @@ and bindings = {
   parent: option<bindings>,
 }
 
+@genType.opaque
 and frame = {
   name: string,
   location: option<Reducer_Peggy_Parse.location>, // can be empty for calls from builtin functions
 }
-
-and frameStack = list<frame>
+@genType.opaque and frameStack = list<frame>
 
 and context = {
   bindings: bindings,
   environment: environment,
-  inFunction: option<string>, // used to build the next frame in frameStack
-  callStack: frameStack,
+  frameStack: frameStack,
+  inFunction: option<lambdaValue>,
 }
 
 and reducerFn = (expression, context) => (value, context)
diff --git a/packages/squiggle-lang/src/rescript/SqError.res b/packages/squiggle-lang/src/rescript/SqError.res
index 461e1feb..29d98517 100644
--- a/packages/squiggle-lang/src/rescript/SqError.res
+++ b/packages/squiggle-lang/src/rescript/SqError.res
@@ -95,19 +95,19 @@ type t = {
 
 exception SqException(t)
 
-// `context` should be specified for runtime errors, but can be left empty for errors from Reducer_Project and so on.
-// `location` can be empty for errors raised from FunctionRegistry.
-let fromMessage = (message: Message.t, frameStack: Reducer_FrameStack.t): t => {
+let fromMessageWithFrameStack = (message: Message.t, frameStack: Reducer_FrameStack.t): t => {
   message: message,
-  stackTrace: stackTrace,
+  frameStack: frameStack,
 }
 
-let fromMessageWithoutFrameStack = (message: Message.t) =>
-  fromMessage(message, Reducer_FrameStack.make())
+// this shouldn't be used much, since frame stack will be empty
+// but it's useful for global errors, e.g. in ReducerProject or somethere in the frontend
+@genType
+let fromMessage = (message: Message.t) =>
+  fromMessageWithFrameStack(message, Reducer_FrameStack.make())
 
 @genType
-let getTopFrame = (t: t): option<Reducer_CallStack.frame> =>
-  t.stackTrace->Reducer_FrameStack.getTopFrame
+let getTopFrame = (t: t): option<Reducer_T.frame> => t.frameStack->Reducer_FrameStack.getTopFrame
 
 @genType
 let getFrameStack = (t: t): Reducer_FrameStack.t => t.frameStack
@@ -116,42 +116,42 @@ let getFrameStack = (t: t): Reducer_FrameStack.t => t.frameStack
 let toString = (t: t): string => t.message->Message.toString
 
 @genType
-let createOtherError = (v: string): t => Message.REOther(v)->fromMessageWithoutFrameStack
+let createOtherError = (v: string): t => Message.REOther(v)->fromMessage
 
 @genType
-let getFrameArray = (t: t): array<Reducer_CallStack.frame> =>
-  t.stackTrace->Reducer_CallStack.toFrameArray
+let getFrameArray = (t: t): array<Reducer_T.frame> => t.frameStack->Reducer_FrameStack.toFrameArray
 
 @genType
-let toStringWithStacktrace = (t: t) =>
+let toStringWithStackTrace = (t: t) =>
   t->toString ++ if t.frameStack->Reducer_FrameStack.isEmpty {
-      "Traceback:\n" ++ t.frameStack->Reducer_FrameStack.toString
+      "\nTraceback:\n" ++ t.frameStack->Reducer_FrameStack.toString
+    } else {
+      ""
     }
 let throw = (t: t) => t->SqException->raise
 
-let throwMessage = (message: Message.t, frameStack: Reducer_FrameStack.t) =>
-  fromMessage(message, frameStack)->throw
+let throwMessageWithFrameStack = (message: Message.t, frameStack: Reducer_FrameStack.t) =>
+  fromMessageWithFrameStack(message, frameStack)->throw
 
 // this shouldn't be used for most runtime errors - the resulting error would have an empty stacktrace
 let fromException = exn =>
   switch exn {
   | SqException(e) => e
-  | Message.MessageException(e) => e->fromMessage(Reducer_CallStack.make())
-  | Js.Exn.Error(obj) =>
-    REJavaScriptExn(obj->Js.Exn.message, obj->Js.Exn.name)->fromMessageWithoutStacktrace
-  | _ => REOther("Unknown exception")->fromMessageWithoutStacktrace
+  | Message.MessageException(e) => e->fromMessage
+  | Js.Exn.Error(obj) => REJavaScriptExn(obj->Js.Exn.message, obj->Js.Exn.name)->fromMessage
+  | _ => REOther("Unknown exception")->fromMessage
   }
 
 // converts raw exceptions into exceptions with stacktrace attached
 // already converted exceptions won't be affected
-let rethrowWithStacktrace = (fn: unit => 'a, stackTrace: Reducer_CallStack.t) => {
+let rethrowWithStacktrace = (fn: unit => 'a, frameStack: Reducer_FrameStack.t) => {
   try {
     fn()
   } catch {
   | SqException(e) => e->throw // exception already has a stacktrace
-  | Message.MessageException(e) => e->throwMessage(stackTrace) // probably comes from FunctionRegistry, adding stacktrace
+  | Message.MessageException(e) => e->throwMessageWithFrameStack(frameStack) // probably comes from FunctionRegistry, adding stacktrace
   | Js.Exn.Error(obj) =>
-    REJavaScriptExn(obj->Js.Exn.message, obj->Js.Exn.name)->throwMessage(stackTrace)
-  | _ => REOther("Unknown exception")->throwMessage(stackTrace)
+    REJavaScriptExn(obj->Js.Exn.message, obj->Js.Exn.name)->throwMessageWithFrameStack(frameStack)
+  | _ => REOther("Unknown exception")->throwMessageWithFrameStack(frameStack)
   }
 }