model the last parts of the EquivalenceRelation module

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

@@ -537,9 +537,15 @@ class ClasslessPredicate extends TClasslessPredicate, Predicate, ModuleDeclarati
       |
         decl order by index
       )
+    or
+    toMock(result) = pred.asRight().getParameter(i)
   }
 
-  override TypeExpr getReturnTypeExpr() { toQL(result) = pred.asLeft().getReturnType() }
+  override TypeExpr getReturnTypeExpr() {
+    toQL(result) = pred.asLeft().getReturnType()
+    or
+    toMock(result) = pred.asRight().getReturnTypeExpr()
+  }
 
   override AstNode getAChild(string pred_name) {
     result = Predicate.super.getAChild(pred_name)

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

@@ -156,8 +156,9 @@ class MockClasslessPredicate extends MockAst {
 
   final string getName() { result = range.getName() }
 
-  // TODO: VarDecl.
-  final MockAst getParameter(int i) { result.getId() = range.getParameter(i) }
+  final MockVarDecl getParameter(int i) { result.getId() = range.getParameter(i) }
+
+  final MockTypeExpr getReturnTypeExpr() { result.getId() = range.getReturnTypeExpr() }
 }
 
 module MockClasslessPredicate {
@@ -170,6 +171,10 @@ module MockClasslessPredicate {
 
     /** Gets the `i`th parameter of the predicate. */
     abstract string getParameter(int i);
+
+    MockTypeExpr::Range getReturnTypeExpr() {
+      none() // may be overridden in subclasses
+    }
   }
 }
 

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

@@ -120,16 +120,16 @@ module QlBuiltinsMocks {
 
   /**
    * A mock that implements the `EquivalenceRelation` module.
-   * The equivalent to the following is implemented: (TODO: WIP, MISSING THE LINES WITH //)
+   * The equivalent to the following is implemented:
    * ```CodeQL
    * module QlBuiltins {
    *  signature class T;
-   *  module EdgeSig<T MyT> {
+   *  module EdgeSig<T MyT> { // This might not be needed.
    *    signature predicate edgeSig(MyT a, MyT b);
    *  }
-   *  module EquivalenceRelation<T MyT, EdgeSig<MyT>::edgeSig/2 edge> { //
-   *    class EquivalenceClass; //
-   *    EquivalenceClass getEquivalenceClass(MyT a); //
+   *  module EquivalenceRelation<T MyT, EdgeSig<MyT>::edgeSig/2 edge> { // the `edge` parameter is not modeled
+   *    class EquivalenceClass;
+   *    EquivalenceClass getEquivalenceClass(MyT a);
    *  }
    *}
    */
@@ -140,6 +140,13 @@ module QlBuiltinsMocks {
       override string getName() { result = "T" }
     }
 
+    /** A mock TypeExpr with classname `T`. */
+    class DummyTTypeExpr extends MockTypeExpr::Range {
+      DummyTTypeExpr() { this = "Mock: QlBuiltins::T" }
+
+      override string getClassName() { result = "T" }
+    }
+
     module EdgeSig {
       class EdgeSigModule extends MockModule::Range {
         EdgeSigModule() { this = "Mock: QlBuiltins::EdgeSig" }
@@ -147,18 +154,12 @@ module QlBuiltinsMocks {
         override string getName() { result = "EdgeSig" }
 
         override predicate hasTypeParam(int i, string type, string name) {
-          i = 0 and name = "MyT" and type instanceof EdgeSigType
+          i = 0 and name = "MyT" and type instanceof DummyTTypeExpr
         }
 
         override string getMember(int i) { i = 0 and result instanceof EdgeSigPred }
       }
 
-      class EdgeSigType extends MockTypeExpr::Range {
-        EdgeSigType() { this = "Mock: QlBuiltins::EdgeSig::MyT" }
-
-        override string getClassName() { result = "MyT" }
-      }
-
       class EdgeSigPred extends MockClasslessPredicate::Range {
         EdgeSigPred() { this = "Mock: QlBuiltins::EdgeSig::edgeSig" }
 
@@ -182,7 +183,7 @@ module QlBuiltinsMocks {
 
         override string getName() { result = name }
 
-        override MockTypeExpr::Range getType() { result instanceof EdgeSigType } // TODO: I'm just using one typeexpr for everything, that might break the parent relation.
+        override MockTypeExpr::Range getType() { result instanceof DummyTTypeExpr }
       }
     }
 
@@ -191,9 +192,50 @@ module QlBuiltinsMocks {
 
       override string getName() { result = "EquivalenceRelation" }
 
-      override MockModule::Range getMember(int i) {
-        none() // TODO: EquivalenceClass/getEquivalenceClass
+      override string getMember(int i) {
+        i = 0 and result instanceof EquivalenceClassClass
+        or
+        i = 1 and result instanceof GetEquivalenceClassPredicate
       }
+
+      override predicate hasTypeParam(int i, string type, string name) {
+        i = 0 and name = "MyT" and type instanceof DummyTTypeExpr
+        or
+        none() // TODO: `EdgeSig<MyT>::edgeSig/2 edge` is not implemented.
+      }
+    }
+
+    class GetEquivalenceClassPredicate extends MockClasslessPredicate::Range {
+      GetEquivalenceClassPredicate() {
+        this = "Mock: QlBuiltins::EquivalenceRelation::getEquivalenceClass"
+      }
+
+      override string getName() { result = "getEquivalenceClass" }
+
+      override MockVarDecl::Range getParameter(int i) {
+        result.(EdgeSig::EdgeSigPredParam).getName() = "a" and // just reusing another mock node that has the right name and type.
+        i = 0
+      }
+
+      override MockTypeExpr::Range getReturnTypeExpr() {
+        result instanceof EquivalenceClassTypeExpr
+      }
+    }
+
+    class EquivalenceClassClass extends MockClass::Range {
+      EquivalenceClassClass() {
+        this = "Mock: QlBuiltins::EquivalenceRelation::EquivalenceClass(Class)"
+      }
+
+      override string getName() { result = "EquivalenceClass" }
+    }
+
+    class EquivalenceClassTypeExpr extends MockTypeExpr::Range {
+      EquivalenceClassTypeExpr() {
+        this = "Mock: QlBuiltins::EquivalenceRelation::EquivalenceClass(TypeExpr)"
+      }
+
+      override string getClassName() { result = "EquivalenceClass" }
     }
   }
 }

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

@@ -322,6 +322,9 @@ predicate resolveTypeExpr2(TypeExpr te, Type t) {
       or
       // e.g. alias for primitives.
       not exists(t.getDeclaration())
+      or
+      // mocks are fine.
+      exists(AstNode decl | decl = t.getDeclaration() | exists(AstNodes::toMock(decl)))
     )
   )
 }

ql/ql/src/queries/diagnostics/EmptyConsistencies.ql

@@ -15,6 +15,7 @@ import codeql_ql.ast.internal.Builtins::BuiltinsConsistency as BuiltinsConsisten
 import codeql_ql.ast.internal.Module::ModConsistency as ModConsistency
 import codeql_ql.ast.internal.Variable::VarConsistency as VarConsistency
 import codeql_ql.ast.internal.AstNodes::AstConsistency as AstConsistency
+import codeql_ql.ast.internal.AstNodes as AstNodes
 
 from AstNode node, string msg
 where
@@ -42,7 +43,9 @@ where
     or
     AstConsistency::nonTotalGetParent(node) and msg = "AstConsistency::nonTotalGetParent"
     or
-    AstConsistency::nonUniqueParent(node) and msg = "AstConsistency::nonUniqueParent"
+    AstConsistency::nonUniqueParent(node) and
+    msg = "AstConsistency::nonUniqueParent" and
+    not exists(AstNodes::toMock(node)) // we don't care about the mocks, they are nasty by design.
     or
     TypeConsistency::noResolve(node) and msg = "TypeConsistency::noResolve"
     or