remove benign result for js/whitespace-contradicts-precedence related to " | 0" expressions

Author: erik-krogh

javascript/ql/src/Expressions/WhitespaceContradictsPrecedence.ql

@@ -61,6 +61,16 @@ class HarmlessNestedExpr extends BinaryExpr {
   }
 }
 
+/**
+ * Holds if contradicting whitespace for `binop` is unlikely to cause confusion.
+ */
+predicate benignWhitespace(BinaryExpr binop) {
+  // asm.js like `expr |0` binary expression.
+  not binop.getParent() instanceof BinaryExpr and
+  binop.getOperator() = "|" and
+  binop.getRightOperand().getIntValue() = 0
+}
+
 /**
  * Holds if `inner` is an operand of `outer`, and the relative precedence
  * may not be immediately clear, but is important for the semantics of
@@ -69,7 +79,8 @@ class HarmlessNestedExpr extends BinaryExpr {
 predicate interestingNesting(BinaryExpr inner, BinaryExpr outer) {
   inner = outer.getAChildExpr() and
   not inner instanceof AssocNestedExpr and
-  not inner instanceof HarmlessNestedExpr
+  not inner instanceof HarmlessNestedExpr and
+  not benignWhitespace(outer)
 }
 
 from BinaryExpr inner, BinaryExpr outer

javascript/ql/test/query-tests/Expressions/WhitespaceContradictsPrecedence/tst.js

@@ -50,3 +50,6 @@ x  +  x >> 1
 
 // OK
 x +   x >> 1
+
+// OK (asm.js-like)
+x = x - 1|0;