From 258e02366fe437c1a4f49edd0608f49261ca0b05 Mon Sep 17 00:00:00 2001
From: jeshecdom <jeshecdom@hotmail.com>
Date: Tue, 31 Dec 2024 15:50:23 +0100
Subject: [PATCH] Small comments and changes in conditions of == and != in
 interpreter.

---
 src/grammar/ast.ts |  3 +++
 src/interpreter.ts | 32 ++++++++++++++++++++++++++++++--
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/src/grammar/ast.ts b/src/grammar/ast.ts
index 85e5c8c8a..455591335 100644
--- a/src/grammar/ast.ts
+++ b/src/grammar/ast.ts
@@ -835,6 +835,9 @@ export function __DANGER_resetNodeId() {
 }
 
 // Test equality of AstExpressions.
+// Note this is syntactical equality of expressions.
+// For example, two struct instances are equal if they have the same
+// type and same fields in the same order.
 export function eqExpressions(
     ast1: AstExpression,
     ast2: AstExpression,
diff --git a/src/interpreter.ts b/src/interpreter.ts
index 07c35b60d..73138e0d5 100644
--- a/src/interpreter.ts
+++ b/src/interpreter.ts
@@ -142,6 +142,28 @@ export function ensureInt(val: AstLiteral): AstNumber {
     }
 }
 
+function ensureArgumentForEquality(val: AstLiteral): AstLiteral {
+    switch (val.kind) {
+        case "address":
+        case "boolean":
+        case "cell":
+        case "comment_value":
+        case "null":
+        case "number":
+        case "simplified_string":
+        case "slice":
+            return val;
+        case "struct_value":
+            throwErrorConstEval(
+                `struct ${showValue(val)} cannot be argument to == operator`,
+                val.loc,
+            );
+            break;
+        default:
+            throwInternalCompilerError("Unrecognized ast literal kind");
+    }
+}
+
 function ensureRepeatInt(val: AstLiteral): AstNumber {
     if (val.kind !== "number") {
         throwErrorConstEval(
@@ -392,7 +414,10 @@ export function evalBinaryOp(
                     source,
                 );
             }
-            const result = eqExpressions(valLeft, valR);
+            const valLeft_ = ensureArgumentForEquality(valLeft);
+            const valR_ = ensureArgumentForEquality(valR);
+
+            const result = eqExpressions(valLeft_, valR_); // Changed to equality testing (instead of ===) because cells, slices, address are equal by hashing
             return makeBooleanLiteral(result, source);
         }
         case "!=": {
@@ -410,7 +435,10 @@ export function evalBinaryOp(
                     source,
                 );
             }
-            const result = !eqExpressions(valLeft, valR);
+            const valLeft_ = ensureArgumentForEquality(valLeft);
+            const valR_ = ensureArgumentForEquality(valR);
+
+            const result = !eqExpressions(valLeft_, valR_); // Changed to equality testing (instead of ===) because cells, slices are equal by hashing
             return makeBooleanLiteral(result, source);
         }
         case "&&": {