Simplify api coverage detection

Fixes a bug that doesn't take super types into account
when computing the usage of a specific API.

java/ql/src/Telemetry/APIUsage.qll

@@ -2,34 +2,25 @@ import java
 private import semmle.code.java.dataflow.FlowSteps
 private import semmle.code.java.dataflow.ExternalFlow
 
-// TODO Is this heuristic too broad?
-predicate isInterestingAPI(Callable call) {
-  call.getNumberOfParameters() > 0 and
-  not (
-    call.getReturnType() instanceof VoidType or
-    call.getReturnType() instanceof PrimitiveType or
-    call.getReturnType() instanceof BoxedType
-  )
-}
-
-// TODO [bm] Fails to detect Collection flow yet (e.g. Map#put)
 string supportKind(Callable api) {
   if api instanceof TaintPreservingCallable
   then result = "taint-preserving"
   else
-    if
-      summaryModel(api.getCompilationUnit().getPackage().toString(),
-        api.getDeclaringType().toString(), _, api.getName(), _, _, _, _, _)
+    if summaryModel(packageName(api), typeName(api), _, api.getName(), _, _, _, _, _)
     then result = "summary"
     else
-      if
-        sinkModel(api.getCompilationUnit().getPackage().toString(),
-          api.getDeclaringType().toString(), _, api.getName(), _, _, _, _)
+      if sinkModel(packageName(api), typeName(api), _, api.getName(), _, _, _, _)
       then result = "sink"
       else
-        if
-          sourceModel(api.getCompilationUnit().getPackage().toString(),
-            api.getDeclaringType().toString(), _, api.getName(), _, _, _, _)
+        if sourceModel(packageName(api), typeName(api), _, api.getName(), _, _, _, _)
         then result = "source"
         else result = "?"
 }
+
+private string packageName(Callable api) {
+  result = api.getCompilationUnit().getPackage().toString()
+}
+
+private string typeName(Callable api) {
+  result = api.getDeclaringType().getAnAncestor().getSourceDeclaration().toString()
+}