feat: support error when comparing with object/array literals

src/compiler/checker.ts

@@ -33975,6 +33975,10 @@ namespace ts {
                 case SyntaxKind.ExclamationEqualsToken:
                 case SyntaxKind.EqualsEqualsEqualsToken:
                 case SyntaxKind.ExclamationEqualsEqualsToken:
+                    if (isLiteralExpressionOfObject(left) || isLiteralExpressionOfObject(right)) {
+                        const eqType = operator === SyntaxKind.EqualsEqualsToken || operator === SyntaxKind.EqualsEqualsEqualsToken;
+                        error(errorNode, Diagnostics.This_condition_will_always_return_0_since_JavaScript_compares_objects_by_reference_not_value, eqType ? "false" : "true");
+                    }
                     reportOperatorErrorUnless((left, right) => isTypeEqualityComparableTo(left, right) || isTypeEqualityComparableTo(right, left));
                     return booleanType;
 

src/compiler/diagnosticMessages.json

@@ -3455,6 +3455,10 @@
         "category": "Error",
         "code": 2838
     },
+    "This condition will always return '{0}' since JavaScript compares objects by reference, not value.": {
+        "category": "Error",
+        "code": 2839
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

src/compiler/utilitiesPublic.ts

@@ -1114,6 +1114,19 @@ namespace ts {
         return isLiteralKind(node.kind);
     }
 
+    /** @internal */
+    export function isLiteralExpressionOfObject(node: Node) {
+        switch (node.kind) {
+            case SyntaxKind.ObjectLiteralExpression:
+            case SyntaxKind.ArrayLiteralExpression:
+            case SyntaxKind.RegularExpressionLiteral:
+            case SyntaxKind.FunctionExpression:
+            case SyntaxKind.ClassExpression:
+                return true;
+        }
+        return false;
+    }
+
     // Pseudo-literals
 
     /* @internal */

tests/baselines/reference/conditionalEqualityOnLiteralObjects.errors.txt

@@ -0,0 +1,130 @@
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(4,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(6,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(8,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(10,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(12,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(14,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(17,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(19,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(21,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(23,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(25,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(27,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(30,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(32,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(34,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(36,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(38,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(40,5): error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(43,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(45,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(47,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(49,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(51,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts(53,5): error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+
+
+==== tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts (24 errors) ====
+    const a = { a: 1 }
+    const b = [1]
+
+    if ({ a: 1 } === { a: 1 }) {
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if ([1] === [1]) {
+        ~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if (a === { a: 1 }) {
+        ~~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if (b === [1]) {
+        ~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if ({ a: 1 } === a) {
+        ~~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if ([1] === b) {
+        ~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+
+    if ({ a: 1 } !== { a: 1 }) {
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if ([1] !== [1]) {
+        ~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if (a !== { a: 1 }) {
+        ~~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if (b !== [1]) {
+        ~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if ({ a: 1 } !== a) {
+        ~~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if ([1] !== b) {
+        ~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+
+    if ({ a: 1 } == { a: 1 }) {
+        ~~~~~~~~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if ([1] == [1]) {
+        ~~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if (a == { a: 1 }) {
+        ~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if (b == [1]) {
+        ~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if ({ a: 1 } == a) {
+        ~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+    if ([1] == b) {
+        ~~~~~~~~
+!!! error TS2839: This condition will always return 'false' since JavaScript compares objects by reference, not value.
+    }
+
+    if ({ a: 1 } != { a: 1 }) {
+        ~~~~~~~~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if ([1] != [1]) {
+        ~~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if (a != { a: 1 }) {
+        ~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if (b != [1]) {
+        ~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if ({ a: 1 } != a) {
+        ~~~~~~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+    if ([1] != b) {
+        ~~~~~~~~
+!!! error TS2839: This condition will always return 'true' since JavaScript compares objects by reference, not value.
+    }
+

tests/baselines/reference/conditionalEqualityOnLiteralObjects.js

@@ -0,0 +1,108 @@
+//// [conditionalEqualityOnLiteralObjects.ts]
+const a = { a: 1 }
+const b = [1]
+
+if ({ a: 1 } === { a: 1 }) {
+}
+if ([1] === [1]) {
+}
+if (a === { a: 1 }) {
+}
+if (b === [1]) {
+}
+if ({ a: 1 } === a) {
+}
+if ([1] === b) {
+}
+
+if ({ a: 1 } !== { a: 1 }) {
+}
+if ([1] !== [1]) {
+}
+if (a !== { a: 1 }) {
+}
+if (b !== [1]) {
+}
+if ({ a: 1 } !== a) {
+}
+if ([1] !== b) {
+}
+
+if ({ a: 1 } == { a: 1 }) {
+}
+if ([1] == [1]) {
+}
+if (a == { a: 1 }) {
+}
+if (b == [1]) {
+}
+if ({ a: 1 } == a) {
+}
+if ([1] == b) {
+}
+
+if ({ a: 1 } != { a: 1 }) {
+}
+if ([1] != [1]) {
+}
+if (a != { a: 1 }) {
+}
+if (b != [1]) {
+}
+if ({ a: 1 } != a) {
+}
+if ([1] != b) {
+}
+
+
+//// [conditionalEqualityOnLiteralObjects.js]
+var a = { a: 1 };
+var b = [1];
+if ({ a: 1 } === { a: 1 }) {
+}
+if ([1] === [1]) {
+}
+if (a === { a: 1 }) {
+}
+if (b === [1]) {
+}
+if ({ a: 1 } === a) {
+}
+if ([1] === b) {
+}
+if ({ a: 1 } !== { a: 1 }) {
+}
+if ([1] !== [1]) {
+}
+if (a !== { a: 1 }) {
+}
+if (b !== [1]) {
+}
+if ({ a: 1 } !== a) {
+}
+if ([1] !== b) {
+}
+if ({ a: 1 } == { a: 1 }) {
+}
+if ([1] == [1]) {
+}
+if (a == { a: 1 }) {
+}
+if (b == [1]) {
+}
+if ({ a: 1 } == a) {
+}
+if ([1] == b) {
+}
+if ({ a: 1 } != { a: 1 }) {
+}
+if ([1] != [1]) {
+}
+if (a != { a: 1 }) {
+}
+if (b != [1]) {
+}
+if ({ a: 1 } != a) {
+}
+if ([1] != b) {
+}

tests/baselines/reference/conditionalEqualityOnLiteralObjects.symbols

@@ -0,0 +1,92 @@
+=== tests/cases/compiler/conditionalEqualityOnLiteralObjects.ts ===
+const a = { a: 1 }
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 11))
+
+const b = [1]
+>b : Symbol(b, Decl(conditionalEqualityOnLiteralObjects.ts, 1, 5))
+
+if ({ a: 1 } === { a: 1 }) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 3, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 3, 18))
+}
+if ([1] === [1]) {
+}
+if (a === { a: 1 }) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 7, 11))
+}
+if (b === [1]) {
+>b : Symbol(b, Decl(conditionalEqualityOnLiteralObjects.ts, 1, 5))
+}
+if ({ a: 1 } === a) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 11, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 5))
+}
+if ([1] === b) {
+>b : Symbol(b, Decl(conditionalEqualityOnLiteralObjects.ts, 1, 5))
+}
+
+if ({ a: 1 } !== { a: 1 }) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 16, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 16, 18))
+}
+if ([1] !== [1]) {
+}
+if (a !== { a: 1 }) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 20, 11))
+}
+if (b !== [1]) {
+>b : Symbol(b, Decl(conditionalEqualityOnLiteralObjects.ts, 1, 5))
+}
+if ({ a: 1 } !== a) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 24, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 5))
+}
+if ([1] !== b) {
+>b : Symbol(b, Decl(conditionalEqualityOnLiteralObjects.ts, 1, 5))
+}
+
+if ({ a: 1 } == { a: 1 }) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 29, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 29, 17))
+}
+if ([1] == [1]) {
+}
+if (a == { a: 1 }) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 33, 10))
+}
+if (b == [1]) {
+>b : Symbol(b, Decl(conditionalEqualityOnLiteralObjects.ts, 1, 5))
+}
+if ({ a: 1 } == a) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 37, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 5))
+}
+if ([1] == b) {
+>b : Symbol(b, Decl(conditionalEqualityOnLiteralObjects.ts, 1, 5))
+}
+
+if ({ a: 1 } != { a: 1 }) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 42, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 42, 17))
+}
+if ([1] != [1]) {
+}
+if (a != { a: 1 }) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 46, 10))
+}
+if (b != [1]) {
+>b : Symbol(b, Decl(conditionalEqualityOnLiteralObjects.ts, 1, 5))
+}
+if ({ a: 1 } != a) {
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 50, 5))
+>a : Symbol(a, Decl(conditionalEqualityOnLiteralObjects.ts, 0, 5))
+}
+if ([1] != b) {
+>b : Symbol(b, Decl(conditionalEqualityOnLiteralObjects.ts, 1, 5))
+}
+