JS: move DeadStoreOfLocal::isDefaultInit to separate module

Esben Sparre Andreasen · Esben Sparre Andreasen · commit cacb8fdee06a · 2018-11-08T13:23:19.000+01:00
diff --git a/javascript/ql/src/Declarations/DeadStore.qll b/javascript/ql/src/Declarations/DeadStore.qll
@@ -0,0 +1,22 @@
+/**
+ * Provides classes and predicates for reasoning about dead stores.
+ */
+
+import javascript
+
+/**
+ * Holds if `e` is an expression that may be used as a default initial value,
+ * such as `0` or `-1`, or an empty object or array literal.
+ */
+predicate isDefaultInit(Expr e) {
+  // primitive default values: zero, false, empty string, and (integer) -1
+  e.(NumberLiteral).getValue().toFloat() = 0.0 or
+  e.(NegExpr).getOperand().(NumberLiteral).getValue() = "1" or
+  e.(ConstantString).getStringValue() = "" or
+  e.(BooleanLiteral).getValue() = "false" or
+  // initialising to an empty array or object literal, even if unnecessary,
+  // can convey useful type information to the reader
+  e.(ArrayExpr).getSize() = 0 or
+  e.(ObjectExpr).getNumProperty() = 0 or
+  SyntacticConstants::isNullOrUndefined(e)
+}
diff --git a/javascript/ql/src/Declarations/DeadStoreOfLocal.ql b/javascript/ql/src/Declarations/DeadStoreOfLocal.ql
@@ -11,6 +11,7 @@
  */
 
 import javascript
+import DeadStore
 
 /**
  * Holds if `vd` is a definition of variable `v` that is dead, that is,
@@ -25,22 +26,6 @@ predicate deadStoreOfLocal(VarDef vd, PurelyLocalVariable v) {
   not exists (SsaExplicitDefinition ssa | ssa.defines(vd, v))
 }
 
-/**
- * Holds if `e` is an expression that may be used as a default initial value,
- * such as `0` or `-1`, or an empty object or array literal.
- */
-predicate isDefaultInit(Expr e) {
-  // primitive default values: zero, false, empty string, and (integer) -1
-  e.(NumberLiteral).getValue().toFloat() = 0.0 or
-  e.(NegExpr).getOperand().(NumberLiteral).getValue() = "1" or
-  e.(ConstantString).getStringValue() = "" or
-  e.(BooleanLiteral).getValue() = "false" or
-  // initialising to an empty array or object literal, even if unnecessary,
-  // can convey useful type information to the reader
-  e.(ArrayExpr).getSize() = 0 or
-  e.(ObjectExpr).getNumProperty() = 0
-}
-
 from VarDef dead, PurelyLocalVariable v  // captured variables may be read by closures, so don't flag them
 where deadStoreOfLocal(dead, v) and
       // the variable should be accessed somewhere; otherwise it will be flagged by UnusedVariable
