numbers: Add proper safety to operator overloading

common/numbers.ts

@@ -137,21 +137,25 @@ export class BigInt extends Uint8Array {
 
   @operator('+')
   plus(other: BigInt): BigInt {
+    assert(this !== null, "Failed to sum BigInts because left hand side is 'null'");
     return bigInt.plus(this, other)
   }
 
   @operator('-')
   minus(other: BigInt): BigInt {
+    assert(this !== null, "Failed to subtract BigInts because left hand side is 'null'");
     return bigInt.minus(this, other)
   }
 
   @operator('*')
   times(other: BigInt): BigInt {
+    assert(this !== null, "Failed to multiply BigInts because left hand side is 'null'");
     return bigInt.times(this, other)
   }
 
   @operator('/')
   div(other: BigInt): BigInt {
+    assert(this !== null, "Failed to divide BigInts because left hand side is 'null'");
     return bigInt.dividedBy(this, other)
   }
 
@@ -161,6 +165,7 @@ export class BigInt extends Uint8Array {
 
   @operator('%')
   mod(other: BigInt): BigInt {
+    assert(this !== null, "Failed to apply module to BigInt because left hand side is 'null'");
     return bigInt.mod(this, other)
   }
 
@@ -319,21 +324,25 @@ export class BigDecimal {
 
   @operator('+')
   plus(other: BigDecimal): BigDecimal {
+    assert(this !== null, "Failed to sum BigDecimals because left hand side is 'null'");
     return bigDecimal.plus(this, other)
   }
 
   @operator('-')
   minus(other: BigDecimal): BigDecimal {
+    assert(this !== null, "Failed to subtract BigDecimals because left hand side is 'null'");
     return bigDecimal.minus(this, other)
   }
 
   @operator('*')
   times(other: BigDecimal): BigDecimal {
+    assert(this !== null, "Failed to multiply BigDecimals because left hand side is 'null'");
     return bigDecimal.times(this, other)
   }
 
   @operator('/')
   div(other: BigDecimal): BigDecimal {
+    assert(this !== null, "Failed to divide BigDecimals because left hand side is 'null'");
     return bigDecimal.dividedBy(this, other)
   }
 
@@ -369,6 +378,7 @@ export class BigDecimal {
 
   @operator.prefix('-')
   neg(): BigDecimal {
+    assert(this !== null, "Failed to negate BigDecimal because the value of it is 'null'");
     return new BigDecimal(new BigInt(0)) - this
   }
 

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@graphprotocol/graph-ts",
   "description": "TypeScript/AssemblyScript library for writing subgraph mappings for The Graph",
-  "version": "0.22.0-alpha.2",
+  "version": "0.22.0-alpha.3",
   "module": "index.ts",
   "types": "index.ts",
   "main": "index.ts",