fix

packages/babel-plugin-transform-typescript/src/enum.ts

@@ -301,6 +301,10 @@ function computeConstantValue(
     } else if (path.isIdentifier()) {
       const name = path.node.name;
 
+      if (["Infinity", "NaN"].includes(name)) {
+        return Number(name);
+      }
+
       let value = prevMembers?.get(name);
       if (value !== undefined) {
         return value;

packages/babel-plugin-transform-typescript/test/fixtures/regression/15768/input.ts

@@ -0,0 +1,11 @@
+const v = 42;
+const v2 = Infinity;
+var Infinity = 1; // Known inconsistencies
+enum StateEnum {
+	okay = 0,
+	neg = -Infinity,
+	pos = Infinity,
+	nan = NaN,
+	ext = v,
+  ext2 = v2,
+}

packages/babel-plugin-transform-typescript/test/fixtures/regression/15768/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["transform-typescript"]
+}

packages/babel-plugin-transform-typescript/test/fixtures/regression/15768/output.js

@@ -0,0 +1,12 @@
+const v = 42;
+const v2 = Infinity;
+var Infinity = 1; // Known inconsistencies
+var StateEnum = /*#__PURE__*/function (StateEnum) {
+  StateEnum[StateEnum["okay"] = 0] = "okay";
+  StateEnum[StateEnum["neg"] = -Infinity] = "neg";
+  StateEnum[StateEnum["pos"] = Infinity] = "pos";
+  StateEnum[StateEnum["nan"] = NaN] = "nan";
+  StateEnum[StateEnum["ext"] = 42] = "ext";
+  StateEnum[StateEnum["ext2"] = 1] = "ext2";
+  return StateEnum;
+}(StateEnum || {});