add a mock TypeExpr, and use it

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

@@ -724,7 +724,7 @@ class FieldDecl extends TFieldDecl, AstNode {
  * A type reference, such as `DataFlow::Node`.
  */
 class TypeExpr extends TType, TypeRef {
-  QL::TypeExpr type;
+  Mocks::TypeExprOrMock type;
 
   TypeExpr() { this = TType(type) }
 
@@ -737,28 +737,30 @@ class TypeExpr extends TType, TypeRef {
    * or db-types such as `@locateable`.
    */
   string getClassName() {
-    result = type.getName().getValue()
+    result = type.asLeft().getName().getValue()
     or
-    result = type.getChild().(QL::PrimitiveType).getValue()
+    result = type.asLeft().getChild().(QL::PrimitiveType).getValue()
     or
-    result = type.getChild().(QL::Dbtype).getValue()
+    result = type.asLeft().getChild().(QL::Dbtype).getValue()
+    or
+    result = type.asRight().getClassName()
   }
 
   /**
    * Holds if this type is a primitive such as `string` or `int`.
    */
-  predicate isPrimitive() { type.getChild() instanceof QL::PrimitiveType }
+  predicate isPrimitive() { type.asLeft().getChild() instanceof QL::PrimitiveType }
 
   /**
    * Holds if this type is a db-type.
    */
-  predicate isDBType() { type.getChild() instanceof QL::Dbtype }
+  predicate isDBType() { type.asLeft().getChild() instanceof QL::Dbtype }
 
   /**
    * Gets the module of the type, if it exists.
    * E.g. `DataFlow` in `DataFlow::Node`.
    */
-  ModuleExpr getModule() { toQL(result) = type.getQualifier() }
+  ModuleExpr getModule() { toQL(result) = type.asLeft().getQualifier() }
 
   /** Gets the type that this type reference refers to. */
   override Type getResolvedType() {
@@ -2400,18 +2402,20 @@ class ModuleExpr extends TModuleExpr, TypeRef {
 
 /** A signature expression, either a `PredicateExpr`, a `TypeExpr`, or a `ModuleExpr`. */
 class SignatureExpr extends TSignatureExpr, AstNode {
-  QL::SignatureExpr sig;
+  Mocks::SignatureExprOrMock sig;
 
   SignatureExpr() {
-    toQL(this) = sig.getPredicate()
+    toQL(this) = sig.asLeft().getPredicate()
     or
-    toQL(this) = sig.getTypeExpr()
+    toQL(this) = sig.asLeft().getTypeExpr()
     or
-    toQL(this) = sig.getModExpr()
+    toMock(this) = sig.asRight()
+    or
+    toQL(this) = sig.asLeft().getModExpr()
   }
 
   /** Gets the generated AST node that contains this signature expression. */
-  QL::SignatureExpr toQL() { result = sig }
+  QL::SignatureExpr toQL() { result = sig.asLeft() }
 
   /** Gets this signature expression if it represents a predicate expression. */
   PredicateExpr asPredicate() { result = this }

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

@@ -16,13 +16,16 @@ private import codeql.util.Either
 // 3: The Either type gets a type without bindingset on the charpred/toString.
 newtype TMockAst =
   TMockModule(string id) { id instanceof MockModule::Range } or
-  TMockClass(string id) { id instanceof MockClass::Range }
+  TMockClass(string id) { id instanceof MockClass::Range } or
+  TMockTypeExpr(string id) { id instanceof MockTypeExpr::Range }
 
 /** Gets a mocked Ast node from the string ID that represents it. */
 MockAst fromId(string id) {
   result = TMockModule(id)
   or
   result = TMockClass(id)
+  or
+  result = TMockTypeExpr(id)
   // TODO: Other nodes.
 }
 
@@ -95,3 +98,44 @@ module MockClass {
 }
 
 class ClassOrMock = Either<QL::Dataclass, MockClass>::Either;
+
+/**
+ * A mocked `SignatureExpr`.
+ * This is special because it is either a `PredicateExpr`, a `TypeExpr`, or a `ModuleExpr`.
+ * // TODO: `PredicateExpr` and `ModuleExpr` are not implemented yet.
+ */
+class MockSignatureExpr extends MockAst {
+  string range;
+
+  MockSignatureExpr() {
+    this = TMockTypeExpr(range)
+    // TODO: or this = TMockPredicateExpr(range)
+    // TODO: or this = TMockModuleExpr(range)
+  }
+}
+
+/**
+ * A mocked `TypeExpr`.
+ * Extend `MockTypeExpr::Range` to add new mocked type expressions.
+ */
+class MockTypeExpr extends MockSignatureExpr, TMockTypeExpr {
+  override MockTypeExpr::Range range;
+
+  MockTypeExpr() { this = TMockTypeExpr(range) }
+
+  final string getClassName() { result = range.getClassName() }
+}
+
+module MockTypeExpr {
+  abstract class Range extends string {
+    bindingset[this]
+    Range() { this = this }
+
+    /** Gets the name of the type. */
+    abstract string getClassName();
+  }
+}
+
+class TypeExprOrMock = Either<QL::TypeExpr, MockTypeExpr>::Either;
+
+class SignatureExprOrMock = Either<QL::SignatureExpr, MockSignatureExpr>::Either;

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

@@ -21,7 +21,7 @@ newtype TAstNode =
   TNewType(QL::Datatype dt) or
   TNewTypeBranch(QL::DatatypeBranch branch) or
   TImport(QL::ImportDirective imp) or
-  TType(QL::TypeExpr type) or
+  TType(Mocks::TypeExprOrMock type) or
   TDisjunction(QL::Disjunction disj) or
   TConjunction(QL::Conjunction conj) or
   TComparisonFormula(QL::CompTerm comp) or
@@ -182,7 +182,7 @@ QL::AstNode toQL(AST::AstNode n) {
   or
   n = TImport(result)
   or
-  n = TType(result)
+  n = TType(any(Mocks::TypeExprOrMock m | m.asLeft() = result))
   or
   n = TAsExpr(result)
   or
@@ -212,7 +212,7 @@ Mocks::MockAst toMock(AST::AstNode n) {
   or
   n = TClass(any(Mocks::ClassOrMock m | m.asRight() = result))
   or
-  none() // TODO: Remove, this is to loosen the type of `toMock` to avoid type-errors in WIP code.
+  n = TType(any(Mocks::TypeExprOrMock m | m.asRight() = result))
 }
 
 class TPredicate =

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

@@ -107,10 +107,12 @@ module QlBuiltinsMocks {
     override string getName() { result = "QlBuiltins" }
 
     override string getMember(int i) {
-      // TODO: InstSig
       i = 0 and
       result instanceof EquivalenceRelation::SigClass
       or
+      i = 1 and
+      result instanceof EquivalenceRelation::EdgeSig::EdgeSigModule
+      or
       i = 2 and
       result instanceof EquivalenceRelation::EquivalenceRelationModule
     }
@@ -122,10 +124,10 @@ module QlBuiltinsMocks {
    * ```CodeQL
    * module QlBuiltins {
    *  signature class T;
-   *  module InstSig<T MyT> { //
+   *  module EdgeSig<T MyT> {
    *    signature predicate edgeSig(MyT a, MyT b); //
    *  }
-   *  module EquivalenceRelation<T MyT, InstSig<MyT>::edgeSig/2 edge> { //
+   *  module EquivalenceRelation<T MyT, EdgeSig<MyT>::edgeSig/2 edge> { //
    *    class EquivalenceClass; //
    *    EquivalenceClass getEquivalenceClass(MyT a); //
    *  }
@@ -138,6 +140,30 @@ module QlBuiltinsMocks {
       override string getName() { result = "T" }
     }
 
+    module EdgeSig {
+      class EdgeSigModule extends MockModule::Range {
+        EdgeSigModule() { this = "Mock: QlBuiltins::EdgeSig" }
+
+        override string getName() { result = "EdgeSig" }
+
+        override predicate hasTypeParam(int i, string type, string name) {
+          i = 0 and name = "MyT" and type instanceof EdgeSigType
+        }
+
+        override string getMember(int i) {
+          // i = 0 and
+          // result instanceof EdgeSig::EdgeSigPredicate
+          none() // TODO:
+        }
+      }
+
+      class EdgeSigType extends MockTypeExpr::Range {
+        EdgeSigType() { this = "Mock: QlBuiltins::EdgeSig::MyT" }
+
+        override string getClassName() { result = "MyT" }
+      }
+    }
+
     class EquivalenceRelationModule extends MockModule::Range {
       EquivalenceRelationModule() { this = "Mock: QlBuiltins::EquivalenceRelation" }