resolve apparent types for equality checks

src/compiler/checker.ts

@@ -17645,6 +17645,8 @@ namespace ts {
                         leftType = leftIsLiteral ? getBaseTypeOfLiteralType(leftType) : leftType;
                         rightType = rightIsLiteral ? getBaseTypeOfLiteralType(rightType) : rightType;
                     }
+                    leftType = getApparentType(leftType);
+                    rightType = getApparentType(rightType);
                     if (!isTypeEqualityComparableTo(leftType, rightType) && !isTypeEqualityComparableTo(rightType, leftType)) {
                         reportOperatorError();
                     }

tests/baselines/reference/test-17428.js

@@ -0,0 +1,10 @@
+//// [test-17428.ts]
+function Generic<T extends string, U extends string>(a: T, b: U) {
+    a == b;
+}
+
+
+//// [test-17428.js]
+function Generic(a, b) {
+    a == b;
+}

tests/baselines/reference/test-17428.symbols

@@ -0,0 +1,15 @@
+=== tests/cases/compiler/test-17428.ts ===
+function Generic<T extends string, U extends string>(a: T, b: U) {
+>Generic : Symbol(Generic, Decl(test-17428.ts, 0, 0))
+>T : Symbol(T, Decl(test-17428.ts, 0, 17))
+>U : Symbol(U, Decl(test-17428.ts, 0, 34))
+>a : Symbol(a, Decl(test-17428.ts, 0, 53))
+>T : Symbol(T, Decl(test-17428.ts, 0, 17))
+>b : Symbol(b, Decl(test-17428.ts, 0, 58))
+>U : Symbol(U, Decl(test-17428.ts, 0, 34))
+
+    a == b;
+>a : Symbol(a, Decl(test-17428.ts, 0, 53))
+>b : Symbol(b, Decl(test-17428.ts, 0, 58))
+}
+

tests/baselines/reference/test-17428.types

@@ -0,0 +1,16 @@
+=== tests/cases/compiler/test-17428.ts ===
+function Generic<T extends string, U extends string>(a: T, b: U) {
+>Generic : <T extends string, U extends string>(a: T, b: U) => void
+>T : T
+>U : U
+>a : T
+>T : T
+>b : U
+>U : U
+
+    a == b;
+>a == b : boolean
+>a : T
+>b : U
+}
+

tests/cases/compiler/test-17428.ts

@@ -0,0 +1,3 @@
+function Generic<T extends string, U extends string>(a: T, b: U) {
+    a == b;
+}