fix: code generation for empty messages (#380)

CHANGELOG.md

@@ -31,6 +31,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - The grammar of the unary operators has been fixed, constant and function declarations are prohibited for contracts and at the top level of Tact modules: PR [#365](https://github.com/tact-lang/tact/pull/365)
 - Typos in ABI generation: : PR [#372](https://github.com/tact-lang/tact/pull/372)
 - `__tact_load_address_opt` code generation: PR [#373](https://github.com/tact-lang/tact/pull/373)
+- Empty messages are now correctly converted into cells: PR [#380](https://github.com/tact-lang/tact/pull/380)
 
 ## [1.3.0] - 2024-05-03
 

src/generator/writers/writeExpression.ts

@@ -61,7 +61,8 @@ function writeStructConstructor(
 
     // Generate constructor
     ctx.fun(name, () => {
-        const sig = `(${resolveFuncType(type, ctx)}) ${name}(${args.map((v) => resolveFuncType(type.fields.find((v2) => v2.name === v)!.type, ctx) + " " + v).join(", ")})`;
+        const funcType = resolveFuncType(type, ctx);
+        const sig = `(${funcType}) ${name}(${args.map((v) => resolveFuncType(type.fields.find((v2) => v2.name === v)!.type, ctx) + " " + v).join(", ")})`;
         ctx.signature(sig);
         ctx.flag("inline");
         ctx.context("type:" + type.name);
@@ -80,7 +81,11 @@ function writeStructConstructor(
                 }
             }, ctx);
 
-            ctx.append(`return (${expressions.join(", ")});`);
+            if (expressions.length === 0 && funcType === "tuple") {
+                ctx.append(`return empty_tuple();`);
+            } else {
+                ctx.append(`return (${expressions.join(", ")});`);
+            }
         });
     });
     return name;

src/test/__snapshots__/bugs.spec.ts.snap

@@ -12,12 +12,12 @@ exports[`bugs should deploy contract correctly 1`] = `
         "$type": "received",
         "message": {
           "body": {
-            "cell": "x{178D45190000000000000000502540BE4008001C6C7938BCE1EDDD4D7179F5626FBC23A92D0521900C93D0E579C0128C1BCFDB0016E3A425A4E75B646191AC9A34FE5D050BD101A5C490F87D01C66D885D09BC1082_}",
+            "cell": "x{178D45190000000000000000502540BE400800C83C40F6E01D9BBE7F089633DC9A2CB62629478287ECE373E35FD9BA1EB951B30016E3A425A4E75B646191AC9A34FE5D050BD101A5C490F87D01C66D885D09BC1082_}",
             "type": "cell",
           },
           "bounce": false,
-          "from": "kQAONjycXnD27qa4vPqxN94R1JaCkMgGSehyvOAJRg3n7ROk",
-          "to": "kQBW5ieoSEHXuEljVf_tAb_cPCvcurQZBoW1ez4bx54-Zadw",
+          "from": "kQBkHiB7cA7N3z-ESxnuTRZbExSjwUP2cbnxr-zdD1yo2V-4",
+          "to": "kQCMrikxzzvzJk9pUSrQW6p1shWQbbH02ChyDiu2JnUvInbG",
           "type": "internal",
           "value": "9.959886",
         },
@@ -38,7 +38,7 @@ exports[`bugs should deploy contract correctly 1`] = `
               },
             },
             "bounce": false,
-            "from": "kQBW5ieoSEHXuEljVf_tAb_cPCvcurQZBoW1ez4bx54-Zadw",
+            "from": "kQCMrikxzzvzJk9pUSrQW6p1shWQbbH02ChyDiu2JnUvInbG",
             "to": "@treasure(treasure)",
             "type": "internal",
             "value": "9.916924834",

src/test/bugs/bugs.tact

@@ -1,5 +1,6 @@
 import "./issue42.tact";
 import "./issue43.tact";
 import "./issue53.tact";
+import "./issue74.tact";
 import "./issue117.tact";
 import "./large-contract.tact";

src/test/bugs/issue74.tact

@@ -0,0 +1,14 @@
+message MyMessage {
+}
+
+contract Issue74 {
+    receive("send") {
+        send(SendParameters {
+            to: context().sender, 
+            value: 0, 
+            bounce: false,
+            mode: SendIgnoreErrors,
+            body: MyMessage {}.toCell()
+        });
+    }
+}