diff --git a/integration/oneof-unions-snake/google/protobuf/struct.ts b/integration/oneof-unions-snake/google/protobuf/struct.ts
index 6e2f28c4e..6c2965c35 100644
--- a/integration/oneof-unions-snake/google/protobuf/struct.ts
+++ b/integration/oneof-unions-snake/google/protobuf/struct.ts
@@ -420,36 +420,43 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
   },
   fromPartial<I extends Exact<DeepPartial<Value>, I>>(object: I): Value {
     const message = createBaseValue();
-    if (
-      object.kind?.$case === "null_value" && object.kind?.null_value !== undefined && object.kind?.null_value !== null
-    ) {
-      message.kind = { $case: "null_value", null_value: object.kind.null_value };
-    } else if (
-      object.kind?.$case === "number_value" &&
-      object.kind?.number_value !== undefined &&
-      object.kind?.number_value !== null
-    ) {
-      message.kind = { $case: "number_value", number_value: object.kind.number_value };
-    } else if (
-      object.kind?.$case === "string_value" &&
-      object.kind?.string_value !== undefined &&
-      object.kind?.string_value !== null
-    ) {
-      message.kind = { $case: "string_value", string_value: object.kind.string_value };
-    } else if (
-      object.kind?.$case === "bool_value" && object.kind?.bool_value !== undefined && object.kind?.bool_value !== null
-    ) {
-      message.kind = { $case: "bool_value", bool_value: object.kind.bool_value };
-    } else if (
-      object.kind?.$case === "struct_value" &&
-      object.kind?.struct_value !== undefined &&
-      object.kind?.struct_value !== null
-    ) {
-      message.kind = { $case: "struct_value", struct_value: object.kind.struct_value };
-    } else if (
-      object.kind?.$case === "list_value" && object.kind?.list_value !== undefined && object.kind?.list_value !== null
-    ) {
-      message.kind = { $case: "list_value", list_value: object.kind.list_value };
+    switch (object.kind?.$case) {
+      case "null_value": {
+        if (object.kind?.null_value !== undefined && object.kind?.null_value !== null) {
+          message.kind = { $case: "null_value", null_value: object.kind.null_value };
+        }
+        break;
+      }
+      case "number_value": {
+        if (object.kind?.number_value !== undefined && object.kind?.number_value !== null) {
+          message.kind = { $case: "number_value", number_value: object.kind.number_value };
+        }
+        break;
+      }
+      case "string_value": {
+        if (object.kind?.string_value !== undefined && object.kind?.string_value !== null) {
+          message.kind = { $case: "string_value", string_value: object.kind.string_value };
+        }
+        break;
+      }
+      case "bool_value": {
+        if (object.kind?.bool_value !== undefined && object.kind?.bool_value !== null) {
+          message.kind = { $case: "bool_value", bool_value: object.kind.bool_value };
+        }
+        break;
+      }
+      case "struct_value": {
+        if (object.kind?.struct_value !== undefined && object.kind?.struct_value !== null) {
+          message.kind = { $case: "struct_value", struct_value: object.kind.struct_value };
+        }
+        break;
+      }
+      case "list_value": {
+        if (object.kind?.list_value !== undefined && object.kind?.list_value !== null) {
+          message.kind = { $case: "list_value", list_value: object.kind.list_value };
+        }
+        break;
+      }
     }
     return message;
   },
diff --git a/integration/oneof-unions-value/google/protobuf/struct.ts b/integration/oneof-unions-value/google/protobuf/struct.ts
index 602beeb67..4bac8e861 100644
--- a/integration/oneof-unions-value/google/protobuf/struct.ts
+++ b/integration/oneof-unions-value/google/protobuf/struct.ts
@@ -417,24 +417,43 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
   },
   fromPartial<I extends Exact<DeepPartial<Value>, I>>(object: I): Value {
     const message = createBaseValue();
-    if (object.kind?.$case === "nullValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
-      message.kind = { $case: "nullValue", value: object.kind.value };
-    } else if (
-      object.kind?.$case === "numberValue" && object.kind?.value !== undefined && object.kind?.value !== null
-    ) {
-      message.kind = { $case: "numberValue", value: object.kind.value };
-    } else if (
-      object.kind?.$case === "stringValue" && object.kind?.value !== undefined && object.kind?.value !== null
-    ) {
-      message.kind = { $case: "stringValue", value: object.kind.value };
-    } else if (object.kind?.$case === "boolValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
-      message.kind = { $case: "boolValue", value: object.kind.value };
-    } else if (
-      object.kind?.$case === "structValue" && object.kind?.value !== undefined && object.kind?.value !== null
-    ) {
-      message.kind = { $case: "structValue", value: object.kind.value };
-    } else if (object.kind?.$case === "listValue" && object.kind?.value !== undefined && object.kind?.value !== null) {
-      message.kind = { $case: "listValue", value: object.kind.value };
+    switch (object.kind?.$case) {
+      case "nullValue": {
+        if (object.kind?.value !== undefined && object.kind?.value !== null) {
+          message.kind = { $case: "nullValue", value: object.kind.value };
+        }
+        break;
+      }
+      case "numberValue": {
+        if (object.kind?.value !== undefined && object.kind?.value !== null) {
+          message.kind = { $case: "numberValue", value: object.kind.value };
+        }
+        break;
+      }
+      case "stringValue": {
+        if (object.kind?.value !== undefined && object.kind?.value !== null) {
+          message.kind = { $case: "stringValue", value: object.kind.value };
+        }
+        break;
+      }
+      case "boolValue": {
+        if (object.kind?.value !== undefined && object.kind?.value !== null) {
+          message.kind = { $case: "boolValue", value: object.kind.value };
+        }
+        break;
+      }
+      case "structValue": {
+        if (object.kind?.value !== undefined && object.kind?.value !== null) {
+          message.kind = { $case: "structValue", value: object.kind.value };
+        }
+        break;
+      }
+      case "listValue": {
+        if (object.kind?.value !== undefined && object.kind?.value !== null) {
+          message.kind = { $case: "listValue", value: object.kind.value };
+        }
+        break;
+      }
     }
     return message;
   },
diff --git a/integration/oneof-unions-value/oneof.ts b/integration/oneof-unions-value/oneof.ts
index 439063cb4..5782a91e6 100644
--- a/integration/oneof-unions-value/oneof.ts
+++ b/integration/oneof-unions-value/oneof.ts
@@ -338,44 +338,64 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
   fromPartial<I extends Exact<DeepPartial<PleaseChoose>, I>>(object: I): PleaseChoose {
     const message = createBasePleaseChoose();
     message.name = object.name ?? "";
-    if (object.choice?.$case === "aNumber" && object.choice?.value !== undefined && object.choice?.value !== null) {
-      message.choice = { $case: "aNumber", value: object.choice.value };
-    } else if (
-      object.choice?.$case === "aString" && object.choice?.value !== undefined && object.choice?.value !== null
-    ) {
-      message.choice = { $case: "aString", value: object.choice.value };
-    } else if (
-      object.choice?.$case === "aMessage" && object.choice?.value !== undefined && object.choice?.value !== null
-    ) {
-      message.choice = { $case: "aMessage", value: PleaseChoose_Submessage.fromPartial(object.choice.value) };
-    } else if (
-      object.choice?.$case === "aBool" && object.choice?.value !== undefined && object.choice?.value !== null
-    ) {
-      message.choice = { $case: "aBool", value: object.choice.value };
-    } else if (
-      object.choice?.$case === "bunchaBytes" && object.choice?.value !== undefined && object.choice?.value !== null
-    ) {
-      message.choice = { $case: "bunchaBytes", value: object.choice.value };
-    } else if (
-      object.choice?.$case === "anEnum" && object.choice?.value !== undefined && object.choice?.value !== null
-    ) {
-      message.choice = { $case: "anEnum", value: object.choice.value };
+    switch (object.choice?.$case) {
+      case "aNumber": {
+        if (object.choice?.value !== undefined && object.choice?.value !== null) {
+          message.choice = { $case: "aNumber", value: object.choice.value };
+        }
+        break;
+      }
+      case "aString": {
+        if (object.choice?.value !== undefined && object.choice?.value !== null) {
+          message.choice = { $case: "aString", value: object.choice.value };
+        }
+        break;
+      }
+      case "aMessage": {
+        if (object.choice?.value !== undefined && object.choice?.value !== null) {
+          message.choice = { $case: "aMessage", value: PleaseChoose_Submessage.fromPartial(object.choice.value) };
+        }
+        break;
+      }
+      case "aBool": {
+        if (object.choice?.value !== undefined && object.choice?.value !== null) {
+          message.choice = { $case: "aBool", value: object.choice.value };
+        }
+        break;
+      }
+      case "bunchaBytes": {
+        if (object.choice?.value !== undefined && object.choice?.value !== null) {
+          message.choice = { $case: "bunchaBytes", value: object.choice.value };
+        }
+        break;
+      }
+      case "anEnum": {
+        if (object.choice?.value !== undefined && object.choice?.value !== null) {
+          message.choice = { $case: "anEnum", value: object.choice.value };
+        }
+        break;
+      }
     }
     message.age = object.age ?? 0;
-    if (
-      object.eitherOr?.$case === "either" && object.eitherOr?.value !== undefined && object.eitherOr?.value !== null
-    ) {
-      message.eitherOr = { $case: "either", value: object.eitherOr.value };
-    } else if (
-      object.eitherOr?.$case === "or" && object.eitherOr?.value !== undefined && object.eitherOr?.value !== null
-    ) {
-      message.eitherOr = { $case: "or", value: object.eitherOr.value };
-    } else if (
-      object.eitherOr?.$case === "thirdOption" &&
-      object.eitherOr?.value !== undefined &&
-      object.eitherOr?.value !== null
-    ) {
-      message.eitherOr = { $case: "thirdOption", value: object.eitherOr.value };
+    switch (object.eitherOr?.$case) {
+      case "either": {
+        if (object.eitherOr?.value !== undefined && object.eitherOr?.value !== null) {
+          message.eitherOr = { $case: "either", value: object.eitherOr.value };
+        }
+        break;
+      }
+      case "or": {
+        if (object.eitherOr?.value !== undefined && object.eitherOr?.value !== null) {
+          message.eitherOr = { $case: "or", value: object.eitherOr.value };
+        }
+        break;
+      }
+      case "thirdOption": {
+        if (object.eitherOr?.value !== undefined && object.eitherOr?.value !== null) {
+          message.eitherOr = { $case: "thirdOption", value: object.eitherOr.value };
+        }
+        break;
+      }
     }
     message.signature = object.signature ?? new Uint8Array(0);
     message.value = object.value ?? undefined;
diff --git a/integration/oneof-unions/google/protobuf/struct.ts b/integration/oneof-unions/google/protobuf/struct.ts
index 66c81b604..8cb68ac9c 100644
--- a/integration/oneof-unions/google/protobuf/struct.ts
+++ b/integration/oneof-unions/google/protobuf/struct.ts
@@ -417,34 +417,43 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
   },
   fromPartial<I extends Exact<DeepPartial<Value>, I>>(object: I): Value {
     const message = createBaseValue();
-    if (object.kind?.$case === "nullValue" && object.kind?.nullValue !== undefined && object.kind?.nullValue !== null) {
-      message.kind = { $case: "nullValue", nullValue: object.kind.nullValue };
-    } else if (
-      object.kind?.$case === "numberValue" &&
-      object.kind?.numberValue !== undefined &&
-      object.kind?.numberValue !== null
-    ) {
-      message.kind = { $case: "numberValue", numberValue: object.kind.numberValue };
-    } else if (
-      object.kind?.$case === "stringValue" &&
-      object.kind?.stringValue !== undefined &&
-      object.kind?.stringValue !== null
-    ) {
-      message.kind = { $case: "stringValue", stringValue: object.kind.stringValue };
-    } else if (
-      object.kind?.$case === "boolValue" && object.kind?.boolValue !== undefined && object.kind?.boolValue !== null
-    ) {
-      message.kind = { $case: "boolValue", boolValue: object.kind.boolValue };
-    } else if (
-      object.kind?.$case === "structValue" &&
-      object.kind?.structValue !== undefined &&
-      object.kind?.structValue !== null
-    ) {
-      message.kind = { $case: "structValue", structValue: object.kind.structValue };
-    } else if (
-      object.kind?.$case === "listValue" && object.kind?.listValue !== undefined && object.kind?.listValue !== null
-    ) {
-      message.kind = { $case: "listValue", listValue: object.kind.listValue };
+    switch (object.kind?.$case) {
+      case "nullValue": {
+        if (object.kind?.nullValue !== undefined && object.kind?.nullValue !== null) {
+          message.kind = { $case: "nullValue", nullValue: object.kind.nullValue };
+        }
+        break;
+      }
+      case "numberValue": {
+        if (object.kind?.numberValue !== undefined && object.kind?.numberValue !== null) {
+          message.kind = { $case: "numberValue", numberValue: object.kind.numberValue };
+        }
+        break;
+      }
+      case "stringValue": {
+        if (object.kind?.stringValue !== undefined && object.kind?.stringValue !== null) {
+          message.kind = { $case: "stringValue", stringValue: object.kind.stringValue };
+        }
+        break;
+      }
+      case "boolValue": {
+        if (object.kind?.boolValue !== undefined && object.kind?.boolValue !== null) {
+          message.kind = { $case: "boolValue", boolValue: object.kind.boolValue };
+        }
+        break;
+      }
+      case "structValue": {
+        if (object.kind?.structValue !== undefined && object.kind?.structValue !== null) {
+          message.kind = { $case: "structValue", structValue: object.kind.structValue };
+        }
+        break;
+      }
+      case "listValue": {
+        if (object.kind?.listValue !== undefined && object.kind?.listValue !== null) {
+          message.kind = { $case: "listValue", listValue: object.kind.listValue };
+        }
+        break;
+      }
     }
     return message;
   },
diff --git a/integration/oneof-unions/oneof.ts b/integration/oneof-unions/oneof.ts
index 8c17b53e3..667bf4ba6 100644
--- a/integration/oneof-unions/oneof.ts
+++ b/integration/oneof-unions/oneof.ts
@@ -338,44 +338,64 @@ export const PleaseChoose: MessageFns<PleaseChoose> = {
   fromPartial<I extends Exact<DeepPartial<PleaseChoose>, I>>(object: I): PleaseChoose {
     const message = createBasePleaseChoose();
     message.name = object.name ?? "";
-    if (object.choice?.$case === "aNumber" && object.choice?.aNumber !== undefined && object.choice?.aNumber !== null) {
-      message.choice = { $case: "aNumber", aNumber: object.choice.aNumber };
-    } else if (
-      object.choice?.$case === "aString" && object.choice?.aString !== undefined && object.choice?.aString !== null
-    ) {
-      message.choice = { $case: "aString", aString: object.choice.aString };
-    } else if (
-      object.choice?.$case === "aMessage" && object.choice?.aMessage !== undefined && object.choice?.aMessage !== null
-    ) {
-      message.choice = { $case: "aMessage", aMessage: PleaseChoose_Submessage.fromPartial(object.choice.aMessage) };
-    } else if (
-      object.choice?.$case === "aBool" && object.choice?.aBool !== undefined && object.choice?.aBool !== null
-    ) {
-      message.choice = { $case: "aBool", aBool: object.choice.aBool };
-    } else if (
-      object.choice?.$case === "bunchaBytes" &&
-      object.choice?.bunchaBytes !== undefined &&
-      object.choice?.bunchaBytes !== null
-    ) {
-      message.choice = { $case: "bunchaBytes", bunchaBytes: object.choice.bunchaBytes };
-    } else if (
-      object.choice?.$case === "anEnum" && object.choice?.anEnum !== undefined && object.choice?.anEnum !== null
-    ) {
-      message.choice = { $case: "anEnum", anEnum: object.choice.anEnum };
+    switch (object.choice?.$case) {
+      case "aNumber": {
+        if (object.choice?.aNumber !== undefined && object.choice?.aNumber !== null) {
+          message.choice = { $case: "aNumber", aNumber: object.choice.aNumber };
+        }
+        break;
+      }
+      case "aString": {
+        if (object.choice?.aString !== undefined && object.choice?.aString !== null) {
+          message.choice = { $case: "aString", aString: object.choice.aString };
+        }
+        break;
+      }
+      case "aMessage": {
+        if (object.choice?.aMessage !== undefined && object.choice?.aMessage !== null) {
+          message.choice = { $case: "aMessage", aMessage: PleaseChoose_Submessage.fromPartial(object.choice.aMessage) };
+        }
+        break;
+      }
+      case "aBool": {
+        if (object.choice?.aBool !== undefined && object.choice?.aBool !== null) {
+          message.choice = { $case: "aBool", aBool: object.choice.aBool };
+        }
+        break;
+      }
+      case "bunchaBytes": {
+        if (object.choice?.bunchaBytes !== undefined && object.choice?.bunchaBytes !== null) {
+          message.choice = { $case: "bunchaBytes", bunchaBytes: object.choice.bunchaBytes };
+        }
+        break;
+      }
+      case "anEnum": {
+        if (object.choice?.anEnum !== undefined && object.choice?.anEnum !== null) {
+          message.choice = { $case: "anEnum", anEnum: object.choice.anEnum };
+        }
+        break;
+      }
     }
     message.age = object.age ?? 0;
-    if (
-      object.eitherOr?.$case === "either" && object.eitherOr?.either !== undefined && object.eitherOr?.either !== null
-    ) {
-      message.eitherOr = { $case: "either", either: object.eitherOr.either };
-    } else if (object.eitherOr?.$case === "or" && object.eitherOr?.or !== undefined && object.eitherOr?.or !== null) {
-      message.eitherOr = { $case: "or", or: object.eitherOr.or };
-    } else if (
-      object.eitherOr?.$case === "thirdOption" &&
-      object.eitherOr?.thirdOption !== undefined &&
-      object.eitherOr?.thirdOption !== null
-    ) {
-      message.eitherOr = { $case: "thirdOption", thirdOption: object.eitherOr.thirdOption };
+    switch (object.eitherOr?.$case) {
+      case "either": {
+        if (object.eitherOr?.either !== undefined && object.eitherOr?.either !== null) {
+          message.eitherOr = { $case: "either", either: object.eitherOr.either };
+        }
+        break;
+      }
+      case "or": {
+        if (object.eitherOr?.or !== undefined && object.eitherOr?.or !== null) {
+          message.eitherOr = { $case: "or", or: object.eitherOr.or };
+        }
+        break;
+      }
+      case "thirdOption": {
+        if (object.eitherOr?.thirdOption !== undefined && object.eitherOr?.thirdOption !== null) {
+          message.eitherOr = { $case: "thirdOption", thirdOption: object.eitherOr.thirdOption };
+        }
+        break;
+      }
     }
     message.signature = object.signature ?? new Uint8Array(0);
     message.value = object.value ?? undefined;
diff --git a/integration/use-readonly-types/google/protobuf/struct.ts b/integration/use-readonly-types/google/protobuf/struct.ts
index a3c773bf5..cde196620 100644
--- a/integration/use-readonly-types/google/protobuf/struct.ts
+++ b/integration/use-readonly-types/google/protobuf/struct.ts
@@ -417,34 +417,43 @@ export const Value: MessageFns<Value> & AnyValueWrapperFns = {
   },
   fromPartial<I extends Exact<DeepPartial<Value>, I>>(object: I): Value {
     const message = createBaseValue() as any;
-    if (object.kind?.$case === "nullValue" && object.kind?.nullValue !== undefined && object.kind?.nullValue !== null) {
-      message.kind = { $case: "nullValue", nullValue: object.kind.nullValue };
-    } else if (
-      object.kind?.$case === "numberValue" &&
-      object.kind?.numberValue !== undefined &&
-      object.kind?.numberValue !== null
-    ) {
-      message.kind = { $case: "numberValue", numberValue: object.kind.numberValue };
-    } else if (
-      object.kind?.$case === "stringValue" &&
-      object.kind?.stringValue !== undefined &&
-      object.kind?.stringValue !== null
-    ) {
-      message.kind = { $case: "stringValue", stringValue: object.kind.stringValue };
-    } else if (
-      object.kind?.$case === "boolValue" && object.kind?.boolValue !== undefined && object.kind?.boolValue !== null
-    ) {
-      message.kind = { $case: "boolValue", boolValue: object.kind.boolValue };
-    } else if (
-      object.kind?.$case === "structValue" &&
-      object.kind?.structValue !== undefined &&
-      object.kind?.structValue !== null
-    ) {
-      message.kind = { $case: "structValue", structValue: object.kind.structValue };
-    } else if (
-      object.kind?.$case === "listValue" && object.kind?.listValue !== undefined && object.kind?.listValue !== null
-    ) {
-      message.kind = { $case: "listValue", listValue: object.kind.listValue };
+    switch (object.kind?.$case) {
+      case "nullValue": {
+        if (object.kind?.nullValue !== undefined && object.kind?.nullValue !== null) {
+          message.kind = { $case: "nullValue", nullValue: object.kind.nullValue };
+        }
+        break;
+      }
+      case "numberValue": {
+        if (object.kind?.numberValue !== undefined && object.kind?.numberValue !== null) {
+          message.kind = { $case: "numberValue", numberValue: object.kind.numberValue };
+        }
+        break;
+      }
+      case "stringValue": {
+        if (object.kind?.stringValue !== undefined && object.kind?.stringValue !== null) {
+          message.kind = { $case: "stringValue", stringValue: object.kind.stringValue };
+        }
+        break;
+      }
+      case "boolValue": {
+        if (object.kind?.boolValue !== undefined && object.kind?.boolValue !== null) {
+          message.kind = { $case: "boolValue", boolValue: object.kind.boolValue };
+        }
+        break;
+      }
+      case "structValue": {
+        if (object.kind?.structValue !== undefined && object.kind?.structValue !== null) {
+          message.kind = { $case: "structValue", structValue: object.kind.structValue };
+        }
+        break;
+      }
+      case "listValue": {
+        if (object.kind?.listValue !== undefined && object.kind?.listValue !== null) {
+          message.kind = { $case: "listValue", listValue: object.kind.listValue };
+        }
+        break;
+      }
     }
     return message;
   },
diff --git a/integration/use-readonly-types/use-readonly-types.ts b/integration/use-readonly-types/use-readonly-types.ts
index a88bb5bf8..a9bcbd5a9 100644
--- a/integration/use-readonly-types/use-readonly-types.ts
+++ b/integration/use-readonly-types/use-readonly-types.ts
@@ -293,18 +293,19 @@ export const Entity: MessageFns<Entity> = {
     message.fieldMask = object.fieldMask ?? undefined;
     message.listValue = object.listValue ?? undefined;
     message.structValue = object.structValue ?? undefined;
-    if (
-      object.oneOfValue?.$case === "theStringValue" &&
-      object.oneOfValue?.theStringValue !== undefined &&
-      object.oneOfValue?.theStringValue !== null
-    ) {
-      message.oneOfValue = { $case: "theStringValue", theStringValue: object.oneOfValue.theStringValue };
-    } else if (
-      object.oneOfValue?.$case === "theIntValue" &&
-      object.oneOfValue?.theIntValue !== undefined &&
-      object.oneOfValue?.theIntValue !== null
-    ) {
-      message.oneOfValue = { $case: "theIntValue", theIntValue: object.oneOfValue.theIntValue };
+    switch (object.oneOfValue?.$case) {
+      case "theStringValue": {
+        if (object.oneOfValue?.theStringValue !== undefined && object.oneOfValue?.theStringValue !== null) {
+          message.oneOfValue = { $case: "theStringValue", theStringValue: object.oneOfValue.theStringValue };
+        }
+        break;
+      }
+      case "theIntValue": {
+        if (object.oneOfValue?.theIntValue !== undefined && object.oneOfValue?.theIntValue !== null) {
+          message.oneOfValue = { $case: "theIntValue", theIntValue: object.oneOfValue.theIntValue };
+        }
+        break;
+      }
     }
     return message;
   },
diff --git a/src/main.ts b/src/main.ts
index 2c73628af..4fdc12157 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -2592,7 +2592,7 @@ function generateFromPartial(ctx: Context, fullName: string, messageDesc: Descri
 
   chunks.push(code`const message = ${createBase}${maybeAsAny(options)};`);
 
-  let currentIfTarget = "";
+  let currentSwitchTarget: string | undefined;
 
   // add a check for each incoming field
   messageDesc.field.forEach((field) => {
@@ -2600,6 +2600,12 @@ function generateFromPartial(ctx: Context, fullName: string, messageDesc: Descri
     const messageProperty = getPropertyAccessor("message", fieldName);
     const objectProperty = getPropertyAccessor("object", fieldName);
 
+    if (currentSwitchTarget && !isWithinOneOfThatShouldBeUnion(options, field)) {
+      // We are exiting a switch, we need to close it
+      chunks.push(code`}`);
+      currentSwitchTarget = undefined;
+    }
+
     const readSnippet = (from: string): Code => {
       if (
         (isLong(field) || isLongValueType(field)) &&
@@ -2710,16 +2716,25 @@ function generateFromPartial(ctx: Context, fullName: string, messageDesc: Descri
       const oneofNameWithObject = getPropertyAccessor("object", oneofName);
       const valueName = oneofValueName(fieldName, options);
       const v = readSnippet(`${oneofNameWithObject}.${valueName}`);
+
+      // If we are entering a new switch, close the previous one
+      if (currentSwitchTarget !== undefined && currentSwitchTarget !== oneofNameWithObject) {
+        chunks.push(code`}`);
+        currentSwitchTarget = undefined;
+      }
+      if (currentSwitchTarget === undefined) {
+        chunks.push(code`switch (${oneofNameWithObject}?.$case) {`);
+      }
       chunks.push(code`
-        ${currentIfTarget === oneofNameWithObject ? "else " : ""}if (
-          ${oneofNameWithObject}?.$case === '${fieldName}'
-          && ${oneofNameWithObject}?.${valueName} !== undefined
-          && ${oneofNameWithObject}?.${valueName} !== null
-        ) {
-          ${oneofNameWithMessage} = { $case: '${fieldName}', ${valueName}: ${v} };
+        case '${fieldName}': {
+          if (${oneofNameWithObject}?.${valueName} !== undefined
+              && ${oneofNameWithObject}?.${valueName} !== null) {
+            ${oneofNameWithMessage} = { $case: '${fieldName}', ${valueName}: ${v} };
+          }
+          break;
         }
       `);
-      currentIfTarget = oneofNameWithObject;
+      currentSwitchTarget = oneofNameWithObject;
     } else if (readSnippet(`x`).toCodeString([]) == "x") {
       // An optimized case of the else below that works when `readSnippet` returns the plain input
       const fallback = isWithinOneOf(field) || noDefaultValue ? "undefined" : defaultValue(ctx, field);
@@ -2734,6 +2749,12 @@ function generateFromPartial(ctx: Context, fullName: string, messageDesc: Descri
     }
   });
 
+  if (currentSwitchTarget) {
+    // We are exiting a switch, we need to close it
+    chunks.push(code`}`);
+    currentSwitchTarget = "";
+  }
+
   // and then wrap up the switch/while/return
   chunks.push(code`return message;`);
   chunks.push(code`}`);