JavaScript: Refactor a few predicates to avoid materialisations.

Author: Max Schaefer

javascript/ql/src/semmle/javascript/dataflow/TypeInference.qll

@@ -254,22 +254,18 @@ class AnalyzedFunction extends DataFlow::AnalyzedValueNode {
    * Gets a return value for a call to this function.
    */
   AbstractValue getAReturnValue() {
-    if astNode.isGenerator() or astNode.isAsync() then
-      result = TAbstractOtherObject()
-    else (
-      // explicit return value
-      result = astNode.getAReturnedExpr().analyze().getALocalValue()
+    // explicit return value
+    result = astNode.getAReturnedExpr().analyze().getALocalValue()
+    or
+    // implicit return value
+    (
+      // either because execution of the function may terminate normally
+      mayReturnImplicitly()
       or
-      // implicit return value
-      (
-        // either because execution of the function may terminate normally
-        mayReturnImplicitly()
-        or
-        // or because there is a bare `return;` statement
-        exists (ReturnStmt ret | ret = astNode.getAReturnStmt() | not exists(ret.getExpr()))
-      ) and
-      result = TAbstractUndefined()
-    )
+      // or because there is a bare `return;` statement
+      exists (ReturnStmt ret | ret = astNode.getAReturnStmt() | not exists(ret.getExpr()))
+    ) and
+    result = TAbstractUndefined()
   }
 
   /**
@@ -288,5 +284,26 @@ class AnalyzedFunction extends DataFlow::AnalyzedValueNode {
       not final instanceof ThrowStmt
     )
   }
+}
+
+/**
+ * Flow analysis for generator functions.
+ */
+private class AnalyzedGeneratorFunction extends AnalyzedFunction {
+  AnalyzedGeneratorFunction() { astNode.isGenerator() }
+
+  override AbstractValue getAReturnValue() {
+    result = TAbstractOtherObject()
+  }
+}
+
+/**
+ * Flow analysis for async functions.
+ */
+private class AnalyzedAsyncFunction extends AnalyzedFunction {
+  AnalyzedAsyncFunction() { astNode.isAsync() }
 
+  override AbstractValue getAReturnValue() {
+    result = TAbstractOtherObject()
+  }
 }

javascript/ql/src/semmle/javascript/dataflow/internal/AbstractPropertiesImpl.qll

@@ -39,16 +39,7 @@ AbstractValue getAnInitialPropertyValue(DefiniteAbstractValue baseVal, string pr
   )
   or
   // class members
-  exists (ClassDefinition c, DataFlow::AnalyzedNode init, MemberDefinition m |
-    m = c.getMember(propertyName) and
-    not m instanceof AccessorMethodDefinition and
-    init = m.getInit().analyze() and
-    result = init.getALocalValue() |
-    if m.isStatic() then
-      baseVal = TAbstractClass(c)
-    else
-      baseVal = AbstractInstance::of(c)
-  )
+  result = getAnInitialMemberValue(getMember(baseVal, propertyName))
   or
   // object properties
   exists (ValueProperty p |
@@ -63,6 +54,30 @@ AbstractValue getAnInitialPropertyValue(DefiniteAbstractValue baseVal, string pr
   result = TAbstractInstance(baseVal)
 }
 
+/**
+ * Gets a class member definition that we abstractly represent as a property of `baseVal`
+ * with the given `name`.
+ */
+private MemberDefinition getMember(DefiniteAbstractValue baseVal, string name) {
+  exists (ClassDefinition c | result = c.getMember(name) |
+    if result.isStatic() then
+      baseVal = TAbstractClass(c)
+    else
+      baseVal = AbstractInstance::of(c)
+  )
+}
+
+/**
+ * Gets an abstract representation of the initial value of member definition `m`.
+ *
+ * For (non-accessor) methods, this is the abstract function corresponding to the
+ * method. For fields, it is an abstract representation of their initial value(s).
+ */
+private AbstractValue getAnInitialMemberValue(MemberDefinition m) {
+  not m instanceof AccessorMethodDefinition and
+  result = m.getInit().analyze().getALocalValue()
+}
+
 /**
  * Holds if `baseVal` is an abstract value whose properties we track for the purposes
  * of `getALocalValue`.