add support for class signatures in parameterized modules

ql/ql/src/codeql_ql/ast/Ast.qll

@@ -2257,6 +2257,12 @@ class SignatureExpr extends TSignatureExpr, AstNode {
 
   /** Gets the generated AST node that contains this signature expression. */
   QL::SignatureExpr toQL() { result = sig }
+
+  /** Gets this signature expression if it represents a predicate expression. */
+  PredicateExpr asPredicate() { result = this }
+
+  /** Gets this signature expression if it represents a type expression. */
+  TypeExpr asType() { result = this }
 }
 
 /** An argument to an annotation. */

ql/ql/src/codeql_ql/ast/internal/Type.qll

@@ -323,6 +323,23 @@ private predicate defines(FileOrModule m, string name, Type t, boolean public) {
     public = getPublicBool(im) and
     defines(im.getResolvedModule(), name, t, true)
   )
+  or
+  // classes in parameterized modules.
+  exists(Module mod, SignatureExpr param, int i |
+    m.asModule() = mod and
+    mod.hasParameter(i, name, param) and
+    public = true
+  |
+    // we resolve it both to the signature type
+    t = param.asType().getResolvedType()
+    or
+    // or any instantiated type
+    exists(ModuleExpr inst, SignatureExpr arg |
+      inst.getArgument(i) = arg and
+      inst.getResolvedModule() = m and
+      t = arg.asType().getResolvedType()
+    )
+  )
 }
 
 module TyConsistency {

ql/ql/test/callgraph/ParamModules.qll

@@ -11,7 +11,19 @@ module PredicateSig {
 }
 
 module ClassSig {
-  // TODO:
+  signature class FooSig extends int;
+
+  module UsesFoo<FooSig FooImpl> {
+    FooImpl getAnEven() { result % 2 = 0 }
+  }
+
+  class MyFoo extends int {
+    MyFoo() { this = [0 .. 10] }
+
+    string myFoo() { result = "myFoo" }
+  }
+
+  string use() { result = UsesFoo<MyFoo>::getAnEven().myFoo() }
 }
 
 module ModuleSig {

ql/ql/test/callgraph/callgraph.expected

@@ -23,6 +23,8 @@ getTarget
 | Overrides.qll:29:3:29:10 | MemberCall | Overrides.qll:8:3:8:41 | ClassPredicate baz |
 | ParamModules.qll:5:28:5:41 | PredicateCall | ParamModules.qll:2:13:2:36 | ClasslessPredicate fooSig |
 | ParamModules.qll:10:26:10:49 | PredicateCall | ParamModules.qll:5:5:5:43 | ClasslessPredicate bar |
+| ParamModules.qll:26:27:26:53 | PredicateCall | ParamModules.qll:17:5:17:42 | ClasslessPredicate getAnEven |
+| ParamModules.qll:26:27:26:61 | MemberCall | ParamModules.qll:23:5:23:39 | ClassPredicate myFoo |
 | packs/other/OtherThing.qll:5:3:5:8 | PredicateCall | packs/lib/LibThing/Foo.qll:1:1:1:30 | ClasslessPredicate foo |
 | packs/other/OtherThing.qll:6:3:6:8 | PredicateCall | packs/src/SrcThing.qll:8:1:8:30 | ClasslessPredicate bar |
 | packs/src/SrcThing.qll:4:3:4:8 | PredicateCall | packs/lib/LibThing/Foo.qll:1:1:1:30 | ClasslessPredicate foo |