From 6540f167c4a9b4003fc3d22b0733f507cfd2c7a4 Mon Sep 17 00:00:00 2001
From: cs01 <cs01@users.noreply.github.com>
Date: Fri, 6 Mar 2026 09:28:06 -0800
Subject: [PATCH] json stringify: nested interfaces, llvm-type resolution,
 member_access dispatch

---
 src/codegen/stdlib/json.ts                    | 48 +++++++++++++++++--
 .../json-stringify-nested-interface.ts        | 24 ++++++++++
 .../json-stringify-parse-roundtrip.ts         | 18 +++++++
 3 files changed, 87 insertions(+), 3 deletions(-)
 create mode 100644 tests/fixtures/builtins/json-stringify-nested-interface.ts
 create mode 100644 tests/fixtures/builtins/json-stringify-parse-roundtrip.ts

diff --git a/src/codegen/stdlib/json.ts b/src/codegen/stdlib/json.ts
index 7a811a0e..7b757ac8 100644
--- a/src/codegen/stdlib/json.ts
+++ b/src/codegen/stdlib/json.ts
@@ -595,14 +595,27 @@ export class JsonGenerator {
     );
   }
 
+  private extractInterfaceFromLlvmType(llvmType: string): string | null {
+    if (llvmType.startsWith("%") && llvmType.endsWith("*")) {
+      return llvmType.slice(1, -1);
+    }
+    return null;
+  }
+
   private resolveInterfaceType(arg: Expression): string | null {
     if (arg.type === "variable") {
       const varNode = arg as { type: string; name: string };
-      return (
+      const fromSymbol =
         this.ctx.symbolTable.getInterfaceType(varNode.name) ||
         this.ctx.symbolTable.getRawInterfaceType(varNode.name) ||
-        null
-      );
+        null;
+      if (fromSymbol) return fromSymbol;
+      const llvmType = this.ctx.getVariableType(varNode.name);
+      if (llvmType) {
+        const extracted = this.extractInterfaceFromLlvmType(llvmType);
+        if (extracted && this.ctx.interfaceStructGenHasInterface(extracted)) return extracted;
+      }
+      return null;
     }
     if (arg.type === "index_access") {
       const indexAccess = arg as { type: string; object: Expression; index: Expression };
@@ -619,6 +632,24 @@ export class JsonGenerator {
         return null;
       }
     }
+    if (arg.type === "member_access") {
+      const memberAccess = arg as { type: string; object: Expression; property: string };
+      const objType = this.resolveInterfaceType(memberAccess.object);
+      if (objType && this.ctx.interfaceStructGenHasInterface(objType)) {
+        const fieldCount = this.ctx.interfaceStructGenGetFieldCount(objType);
+        for (let i = 0; i < fieldCount; i++) {
+          const rawName = this.ctx.interfaceStructGenGetFieldName(objType, i);
+          const fName =
+            rawName.charAt(rawName.length - 1) === "?"
+              ? rawName.substring(0, rawName.length - 1)
+              : rawName;
+          if (fName === memberAccess.property) {
+            const fTsType = this.ctx.interfaceStructGenGetFieldTsType(objType, i);
+            if (this.ctx.interfaceStructGenHasInterface(fTsType)) return fTsType;
+          }
+        }
+      }
+    }
     return null;
   }
 
@@ -697,6 +728,17 @@ export class JsonGenerator {
           "@csyyjson_obj_add_bool",
           `i8* ${jsonDoc}, i8* ${jsonObj}, i8* ${nameConst}, i32 ${boolInt}`,
         );
+      } else if (this.ctx.interfaceStructGenHasInterface(fieldTsType)) {
+        const nestedPtr = this.ctx.emitLoad("i8*", fieldPtr);
+        const nestedFieldCount = this.ctx.interfaceStructGenGetFieldCount(fieldTsType);
+        const nestedStructType = this.buildStructType(fieldTsType, nestedFieldCount);
+        const nestedTyped = this.ctx.emitBitcast(nestedPtr, "i8*", `${nestedStructType}*`);
+        const subObj = this.ctx.emitCall(
+          "i8*",
+          "@csyyjson_obj_add_obj",
+          `i8* ${jsonDoc}, i8* ${jsonObj}, i8* ${nameConst}`,
+        );
+        this.emitAddFieldsToJsonObj(nestedTyped, nestedStructType, fieldTsType, jsonDoc, subObj);
       } else {
         const val = this.ctx.emitLoad("double", fieldPtr);
         this.ctx.emitCallVoid(
diff --git a/tests/fixtures/builtins/json-stringify-nested-interface.ts b/tests/fixtures/builtins/json-stringify-nested-interface.ts
new file mode 100644
index 00000000..c46d9326
--- /dev/null
+++ b/tests/fixtures/builtins/json-stringify-nested-interface.ts
@@ -0,0 +1,24 @@
+// @test-description: json stringify nested interface fields
+
+interface Address {
+  street: string;
+  zip: string;
+}
+
+interface Person {
+  name: string;
+  age: number;
+  address: Address;
+}
+
+const addr: Address = { street: "123 Main St", zip: "90210" };
+const person: Person = { name: "Alice", age: 30, address: addr };
+
+const json = JSON.stringify(person);
+const parsed = JSON.parse<Person>(json);
+
+if (parsed.name === "Alice" && parsed.age === 30) {
+  console.log("TEST_PASSED");
+} else {
+  console.log("FAIL");
+}
diff --git a/tests/fixtures/builtins/json-stringify-parse-roundtrip.ts b/tests/fixtures/builtins/json-stringify-parse-roundtrip.ts
new file mode 100644
index 00000000..f876c92d
--- /dev/null
+++ b/tests/fixtures/builtins/json-stringify-parse-roundtrip.ts
@@ -0,0 +1,18 @@
+// @test-description: json stringify of a json parse result (llvm type tracking)
+
+interface Config {
+  host: string;
+  port: number;
+  debug: boolean;
+}
+
+const raw = '{"host":"localhost","port":8080,"debug":1}';
+const cfg = JSON.parse<Config>(raw);
+const out = JSON.stringify(cfg);
+const cfg2 = JSON.parse<Config>(out);
+
+if (cfg2.host === "localhost" && cfg2.port === 8080) {
+  console.log("TEST_PASSED");
+} else {
+  console.log("FAIL: " + cfg2.host + " " + cfg2.port);
+}