Improved undefined/null handling for unary operators

Author: ahejlsberg

src/compiler/checker.ts

@@ -14483,6 +14483,7 @@ namespace ts {
                 case SyntaxKind.PlusToken:
                 case SyntaxKind.MinusToken:
                 case SyntaxKind.TildeToken:
+                    checkNonNullType(operandType, node.operand);
                     if (maybeTypeOfKind(operandType, TypeFlags.ESSymbol)) {
                         error(node.operand, Diagnostics.The_0_operator_cannot_be_applied_to_type_symbol, tokenToString(node.operator));
                     }
@@ -14494,7 +14495,7 @@ namespace ts {
                         booleanType;
                 case SyntaxKind.PlusPlusToken:
                 case SyntaxKind.MinusMinusToken:
-                    const ok = checkArithmeticOperandType(node.operand, getNonNullableType(operandType),
+                    const ok = checkArithmeticOperandType(node.operand, checkNonNullType(operandType, node.operand),
                         Diagnostics.An_arithmetic_operand_must_be_of_type_any_number_or_an_enum_type);
                     if (ok) {
                         // run check only if former checks succeeded to avoid reporting cascading errors
@@ -14510,7 +14511,7 @@ namespace ts {
             if (operandType === silentNeverType) {
                 return silentNeverType;
             }
-            const ok = checkArithmeticOperandType(node.operand, getNonNullableType(operandType),
+            const ok = checkArithmeticOperandType(node.operand, checkNonNullType(operandType, node.operand),
                 Diagnostics.An_arithmetic_operand_must_be_of_type_any_number_or_an_enum_type);
             if (ok) {
                 // run check only if former checks succeeded to avoid reporting cascading errors