Merge pull request #18320 from jketema/template-parameters

C++: Support non-type template parameters

Author: jketema

cpp/downgrades/d6a03a00b9824f27241b58b8e18208f31c03904a/old.dbscheme

@@ -0,0 +1,3 @@
+description: Support non-type template parameters
+compatibility: full
+nontype_template_parameters.rel: delete

cpp/downgrades/d6a03a00b9824f27241b58b8e18208f31c03904a/semmlecode.cpp.dbscheme

@@ -0,0 +1,4 @@
+---
+category: feature
+---
+* A new class `NonTypeTemplateParameter` was introduced, which represents C++ non-type template parameters.

cpp/downgrades/d6a03a00b9824f27241b58b8e18208f31c03904a/upgrade.properties

@@ -35,6 +35,7 @@ import semmle.code.cpp.Field
 import semmle.code.cpp.Function
 import semmle.code.cpp.MemberFunction
 import semmle.code.cpp.Parameter
+import semmle.code.cpp.TemplateParameter
 import semmle.code.cpp.Variable
 import semmle.code.cpp.Initializer
 import semmle.code.cpp.FriendDecl

cpp/ql/lib/change-notes/2024-12-18-non-type-template-parameter.md

@@ -0,0 +1,92 @@
+/**
+ * Provides a hierarchy of classes for modeling C/C++ template parameters.
+ */
+
+import semmle.code.cpp.Type
+private import semmle.code.cpp.internal.ResolveClass
+
+abstract private class TemplateParameterImpl extends Locatable {
+  override string getAPrimaryQlClass() { result = "TemplateParameterImpl" }
+}
+
+/**
+ * A C++ template parameter.
+ *
+ * In the example below, `T`, `TT`, and `I` are template parameters:
+ * ```
+ * template <class T, template<typename> TT, int I>
+ * class C { };
+ * ```
+ */
+final class TemplateParameterBase = TemplateParameterImpl;
+
+/**
+ * A C++ non-type template parameter.
+ *
+ * In the example below, `I` is a non-type template parameter:
+ * ```
+ * template <int I>
+ * class C { };
+ * ```
+ */
+class NonTypeTemplateParameter extends Literal, TemplateParameterImpl {
+  NonTypeTemplateParameter() { nontype_template_parameters(underlyingElement(this)) }
+
+  override string getAPrimaryQlClass() { result = "NonTypeTemplateParameter" }
+}
+
+/**
+ * A C++ `typename` (or `class`) template parameter.
+ *
+ * DEPRECATED: Use `TypeTemplateParameter` instead.
+ */
+deprecated class TemplateParameter = TypeTemplateParameter;
+
+/**
+ * A C++ `typename` (or `class`) template parameter.
+ *
+ * In the example below, `T` is a template parameter:
+ * ```
+ * template <class T>
+ * class C { };
+ * ```
+ */
+class TypeTemplateParameter extends UserType, TemplateParameterImpl {
+  TypeTemplateParameter() {
+    usertypes(underlyingElement(this), _, 7) or usertypes(underlyingElement(this), _, 8)
+  }
+
+  override string getAPrimaryQlClass() { result = "TypeTemplateParameter" }
+
+  override predicate involvesTemplateParameter() { any() }
+}
+
+/**
+ * A C++ template template parameter.
+ *
+ * In the example below, `T` is a template template parameter (although its name
+ * may be omitted):
+ * ```
+ * template <template <typename T> class Container, class Elem>
+ * void foo(const Container<Elem> &value) { }
+ * ```
+ */
+class TemplateTemplateParameter extends TypeTemplateParameter {
+  TemplateTemplateParameter() { usertypes(underlyingElement(this), _, 8) }
+
+  override string getAPrimaryQlClass() { result = "TemplateTemplateParameter" }
+}
+
+/**
+ * A type representing the use of the C++11 `auto` keyword.
+ * ```
+ * auto val = some_typed_expr();
+ * ```
+ */
+class AutoType extends TypeTemplateParameter {
+  AutoType() { usertypes(underlyingElement(this), "auto", 7) }
+
+  override string getAPrimaryQlClass() { result = "AutoType" }
+
+  override Location getLocation() { result instanceof UnknownDefaultLocation }
+}

cpp/ql/lib/cpp.qll

@@ -4,6 +4,7 @@
 
 import semmle.code.cpp.Element
 import semmle.code.cpp.Function
+import semmle.code.cpp.TemplateParameter
 private import semmle.code.cpp.internal.ResolveClass
 
 /**
@@ -288,10 +289,7 @@ class Type extends Locatable, @type {
    */
   Type stripType() { result = this }
 
-  override Location getLocation() {
-    suppressUnusedThis(this) and
-    result instanceof UnknownDefaultLocation
-  }
+  override Location getLocation() { result instanceof UnknownDefaultLocation }
 }
 
 /**
@@ -1666,82 +1664,6 @@ class RoutineType extends Type, @routinetype {
   }
 }
 
-abstract private class TemplateParameterImpl extends Locatable {
-  override string getAPrimaryQlClass() { result = "TemplateParameterImpl" }
-}
-
-/**
- * A C++ template parameter.
- *
- * In the example below, `T`, `TT`, and `I` are template parameters:
- * ```
- * template <class T, template<typename> TT, int I>
- * class C { };
- * ```
- */
-final class TemplateParameterBase = TemplateParameterImpl;
-
-/**
- * A C++ `typename` (or `class`) template parameter.
- *
- * DEPRECATED: Use `TypeTemplateParameter` instead.
- */
-deprecated class TemplateParameter = TypeTemplateParameter;
-
-/**
- * A C++ `typename` (or `class`) template parameter.
- *
- * In the example below, `T` is a template parameter:
- * ```
- * template <class T>
- * class C { };
- * ```
- */
-class TypeTemplateParameter extends UserType, TemplateParameterImpl {
-  TypeTemplateParameter() {
-    usertypes(underlyingElement(this), _, 7) or usertypes(underlyingElement(this), _, 8)
-  }
-
-  override string getAPrimaryQlClass() { result = "TypeTemplateParameter" }
-
-  override predicate involvesTemplateParameter() { any() }
-}
-
-/**
- * A C++ template template parameter.
- *
- * In the example below, `T` is a template template parameter (although its name
- * may be omitted):
- * ```
- * template <template <typename T> class Container, class Elem>
- * void foo(const Container<Elem> &value) { }
- * ```
- */
-class TemplateTemplateParameter extends TypeTemplateParameter {
-  TemplateTemplateParameter() { usertypes(underlyingElement(this), _, 8) }
-
-  override string getAPrimaryQlClass() { result = "TemplateTemplateParameter" }
-}
-
-/**
- * A type representing the use of the C++11 `auto` keyword.
- * ```
- * auto val = some_typed_expr();
- * ```
- */
-class AutoType extends TypeTemplateParameter {
-  AutoType() { usertypes(underlyingElement(this), "auto", 7) }
-
-  override string getAPrimaryQlClass() { result = "AutoType" }
-
-  override Location getLocation() {
-    suppressUnusedThis(this) and
-    result instanceof UnknownDefaultLocation
-  }
-}
-
-private predicate suppressUnusedThis(Type t) { any() }
-
 /**
  * A source code location referring to a user-defined type.
  *

cpp/ql/lib/semmle/code/cpp/TemplateParameter.qll

@@ -785,6 +785,10 @@ usertype_uuid(
     string uuid: string ref
 );
 
+nontype_template_parameters(
+    int id: @expr ref
+);
+
 mangled_name(
     unique int id: @declaration ref,
     int mangled_name : @mangledname,