fix(codegen): emptyMap() in equality comparisons (tact-lang#814)

CHANGELOG.md

@@ -37,6 +37,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Message opcodes are now checked if they fit into 32 bits: PR [#771](https://github.com/tact-lang/tact/pull/771)
 - Disallow zero binary message opcodes as those are reserved for text messages: PR [#786](https://github.com/tact-lang/tact/pull/786)
 - Return-statements in `init()` function do not cause FunC compilation error anymore: PR [#794](https://github.com/tact-lang/tact/pull/794)
+- `emptyMap()` in equality comparison expressions does not cause code generation failures: PR [#814](https://github.com/tact-lang/tact/pull/814)
 
 ## [1.4.4] - 2024-08-18
 

src/generator/writers/writeExpression.ts

@@ -44,8 +44,8 @@ import { writeCastedExpression } from "./writeFunction";
 import { evalConstantExpression } from "../../constEval";
 import { isLvalue } from "../../types/resolveStatements";
 
-function isNull(f: AstExpression): boolean {
-    return f.kind === "null";
+function isNull(wCtx: WriterContext, expr: AstExpression): boolean {
+    return getExpType(wCtx.ctx, expr).kind === "null";
 }
 
 function writeStructConstructor(
@@ -213,23 +213,23 @@ export function writeExpression(f: AstExpression, wCtx: WriterContext): string {
         return funcIdOf(f.text);
     }
 
-    // NOTE: We always wrap in parentheses to avoid operator precedence issues
+    // NOTE: We always wrap expressions in parentheses to avoid operator precedence issues
     if (f.kind === "op_binary") {
         // Special case for non-integer types and nullable
         if (f.op === "==" || f.op === "!=") {
-            if (isNull(f.left) && isNull(f.right)) {
+            if (isNull(wCtx, f.left) && isNull(wCtx, f.right)) {
                 if (f.op === "==") {
                     return "true";
                 } else {
                     return "false";
                 }
-            } else if (isNull(f.left) && !isNull(f.right)) {
+            } else if (isNull(wCtx, f.left) && !isNull(wCtx, f.right)) {
                 if (f.op === "==") {
                     return `null?(${writeExpression(f.right, wCtx)})`;
                 } else {
                     return `(~ null?(${writeExpression(f.right, wCtx)}))`;
                 }
-            } else if (!isNull(f.left) && isNull(f.right)) {
+            } else if (!isNull(wCtx, f.left) && isNull(wCtx, f.right)) {
                 if (f.op === "==") {
                     return `null?(${writeExpression(f.left, wCtx)})`;
                 } else {
@@ -384,7 +384,7 @@ export function writeExpression(f: AstExpression, wCtx: WriterContext): string {
 
     //
     // Unary operations: !, -, +, !!
-    // NOTE: We always wrap in parenthesis to avoid operator precedence issues
+    // NOTE: We always wrap expressions in parentheses to avoid operator precedence issues
     //
 
     if (f.kind === "op_unary") {

src/test/codegen/all-contracts.tact

@@ -6,4 +6,5 @@ import "./message-opcode-parsing.tact";
 import "./struct-with-default-and-optional-fields";
 import "./mutating-method-on-non-lvalues";
 import "./var-scope-global-fun-shadowing-allowed";
-import "./map-uint-bool-get";
+import "./map-uint-bool-get";
+import "./emptyMap-in-equality";

src/test/codegen/emptyMap-in-equality.tact

@@ -0,0 +1,8 @@
+contract TestContract {
+    get fun testEq(s: map<Int,Int>): Bool {
+        return s == emptyMap();
+    }
+    get fun testNeq(s: map<Int,Int>): Bool {
+        return s != emptyMap();
+    }
+}