deal with eval errors

src/component/app/App.tsx

@@ -8,6 +8,8 @@ import { biggerExample, emptySet, factorial, higherOrder, higherOrder2Params, in
 
 import './App.css';
 import { evalExpr } from '../../eval/eval';
+import { Value } from '../other/Value';
+import { Type } from '../other/Type';
 
 
 const examples: [string, ExprBlockState][] = [
@@ -182,7 +184,13 @@ export function App() {
             }}
             typeInfo={typeInfo}
           />
-          ={evalExpr(currentState, extendedEnv)}
+          =
+          <Value dynamic={{
+            i: evalExpr(currentState, extendedEnv),
+            t: typeInfo.type,
+          }}/>
+          ::
+          <Type type={typeInfo.type}/>
         </GlobalContext>
       </main>
 

src/component/other/Type.tsx

@@ -1,8 +1,13 @@
 import { getHumanReadableName, getSymbol, symbolDict, symbolDictIterator, symbolFunction, symbolList, symbolProduct, symbolSet, symbolSetIterator, symbolSum } from "dope2";
 
 import "./Type.css";
+import { ValueUnknown } from "./Value";
 
 export function Type({type}) {
+  if (type === undefined) {
+    // Types are just values, and sometimes, when using a Type as a Value, the Type is unknown (e.g., because of an eval error when computing the type)
+    return <ValueUnknown/>;
+  }
   const symbol = getSymbol(type);
   switch (symbol) {
     case symbolFunction:

src/component/other/Value.css

@@ -16,4 +16,8 @@
   margin-right: 2px;
   padding-left: 2px;
   padding-right: 2px;
+}
+
+.valueUnknown {
+  color: darkgrey;
 }

src/component/other/Value.tsx

@@ -1,4 +1,4 @@
-import {getType, getInst, getSymbol, Double, Int, symbolFunction, symbolProduct, symbolSum, symbolDict, symbolSet, symbolList, eqType, match, getLeft, getRight, dict, Bool, set, Unit, symbolType, symbolUUID, getHumanReadableName, Ordering} from "dope2";
+import {getType, getInst, getSymbol, Double, Int, symbolFunction, symbolProduct, symbolSum, symbolDict, symbolSet, symbolList, eqType, match, getLeft, getRight, dict, Bool, set, Unit, symbolType, symbolUUID, getHumanReadableName, Ordering, isTypeVar} from "dope2";
 
 import "./Value.css";
 import { Type } from "./Type";
@@ -6,6 +6,11 @@ import { Type } from "./Type";
 export function Value({dynamic}) {
   const type = getType(dynamic);
   const inst = getInst(dynamic);
+  if (inst === undefined) {
+    // Sometimes we only know the type of a value, not the value itself.
+    // For instance, if there is an evaluation error somewhere.
+    return <ValueUnknown/>;
+  }
   if (eqType(type)(Double)) {
     return <ValueDouble val={inst}/>;
   }
@@ -87,4 +92,7 @@ function ValueUUID({val}) {
 }
 function ValueOrdering({val}) {
   return <span className="valueOrdering">{{[-1]: "LessThan", [0]: "Equal", [1]: "GreaterThan" }[val]}</span>
+}
+export function ValueUnknown() {
+  return <span className="valueUnknown">unknown</span>
 }

src/eval/eval.ts

@@ -49,7 +49,10 @@ export function evalCall(s: CallBlockState, env: DynamicEnvironment): EvalResult
   const fn = evalExpr(s.fn, env);
   const input = evalExpr(s.input, env);
   if (fn !== undefined && input !== undefined) {
-    return fn(input);
+    try {
+      return fn(input);
+    }
+    catch {}
   }
 }