From 3b6878da3ded77aa86ee1032c84900633cfad236 Mon Sep 17 00:00:00 2001
From: Jeroen Ketema <jketema@github.com>
Date: Thu, 26 Dec 2024 11:12:17 +0100
Subject: [PATCH] C++: Add support for requires clauses and constraints on
 template parameters

---
 cpp/ql/lib/semmle/code/cpp/Function.qll       | 21 +++++++++++++++
 .../lib/semmle/code/cpp/TemplateParameter.qll |  7 +++++
 cpp/ql/lib/semmle/code/cpp/UserType.qll       |  5 ++++
 cpp/ql/lib/semmle/code/cpp/Variable.qll       |  5 ++++
 cpp/ql/lib/semmlecode.cpp.dbscheme            | 27 +++++++++++++++++++
 5 files changed, 65 insertions(+)

diff --git a/cpp/ql/lib/semmle/code/cpp/Function.qll b/cpp/ql/lib/semmle/code/cpp/Function.qll
index d2caa56c9f8c8..cb3b00b64ade9 100644
--- a/cpp/ql/lib/semmle/code/cpp/Function.qll
+++ b/cpp/ql/lib/semmle/code/cpp/Function.qll
@@ -715,6 +715,27 @@ class FunctionDeclarationEntry extends DeclarationEntry, @fun_decl {
    * specification.
    */
   predicate isNoExcept() { fun_decl_empty_noexcept(underlyingElement(this)) }
+
+  /**
+   * Gets a requires clause if this declaration is a template with such a clause.
+   */
+  Expr getARequiresClause() { fun_requires(underlyingElement(this), _, unresolveElement(result)) }
+
+  /**
+   * Gets the requires clause that appears after the template argument list if this
+   * declaration is a template with such a clause.
+   */
+  Expr getTemplateRequiresClause() {
+    fun_requires(underlyingElement(this), 1, unresolveElement(result))
+  }
+
+  /**
+   * Gets the requires clause that appears after the declarator if this declaration
+   * is a template with such a clause.
+   */
+  Expr getFunctionRequiresClause() {
+    fun_requires(underlyingElement(this), 2, unresolveElement(result))
+  }
 }
 
 /**
diff --git a/cpp/ql/lib/semmle/code/cpp/TemplateParameter.qll b/cpp/ql/lib/semmle/code/cpp/TemplateParameter.qll
index c127af22a9d63..d6c4b1a8121a1 100644
--- a/cpp/ql/lib/semmle/code/cpp/TemplateParameter.qll
+++ b/cpp/ql/lib/semmle/code/cpp/TemplateParameter.qll
@@ -59,6 +59,13 @@ class TypeTemplateParameter extends UserType, TemplateParameterImpl {
   override string getAPrimaryQlClass() { result = "TypeTemplateParameter" }
 
   override predicate involvesTemplateParameter() { any() }
+
+  /**
+   * Get the type constraint of this type template parameter.
+   */
+  Expr getTypeConstraint() {
+    type_template_type_constraint(underlyingElement(this), unresolveElement(result))
+  }
 }
 
 /**
diff --git a/cpp/ql/lib/semmle/code/cpp/UserType.qll b/cpp/ql/lib/semmle/code/cpp/UserType.qll
index 9d85f555ec1af..439ed84e05e84 100644
--- a/cpp/ql/lib/semmle/code/cpp/UserType.qll
+++ b/cpp/ql/lib/semmle/code/cpp/UserType.qll
@@ -129,4 +129,9 @@ class TypeDeclarationEntry extends DeclarationEntry, @type_decl {
    * class or typedef.
    */
   predicate isTopLevel() { type_decl_top(underlyingElement(this)) }
+
+  /**
+   * Gets the requires clause if this declaration is a template with such a clause.
+   */
+  Expr getRequiresClause() { type_requires(underlyingElement(this), unresolveElement(result)) }
 }
diff --git a/cpp/ql/lib/semmle/code/cpp/Variable.qll b/cpp/ql/lib/semmle/code/cpp/Variable.qll
index 3bf408820fcba..8e68cc1927f72 100644
--- a/cpp/ql/lib/semmle/code/cpp/Variable.qll
+++ b/cpp/ql/lib/semmle/code/cpp/Variable.qll
@@ -278,6 +278,11 @@ class VariableDeclarationEntry extends DeclarationEntry, @var_decl {
 
   /** Holds if this declaration is a template specialization. */
   predicate isSpecialization() { var_specialized(underlyingElement(this)) }
+
+  /**
+   * Gets the requires clause if this declaration is a template with such a clause.
+   */
+  Expr getRequiresClause() { var_requires(underlyingElement(this), unresolveElement(result)) }
 }
 
 /**
diff --git a/cpp/ql/lib/semmlecode.cpp.dbscheme b/cpp/ql/lib/semmlecode.cpp.dbscheme
index 9a9d9e573a326..8b8d0274ce0ab 100644
--- a/cpp/ql/lib/semmlecode.cpp.dbscheme
+++ b/cpp/ql/lib/semmlecode.cpp.dbscheme
@@ -480,6 +480,20 @@ fun_decl_typedef_type(
     int typedeftype_id: @usertype ref
 );
 
+/*
+case @fun_requires.kind of
+  1 = @template_attached
+| 2 = @function_attached
+;
+*/
+
+#keyset[id, kind]
+fun_requires(
+    int id: @fun_decl ref,
+    int kind: int ref,
+    int constraint: @expr ref
+);
+
 param_decl_bind(
     unique int id: @var_decl ref,
     int index: int ref,
@@ -501,6 +515,10 @@ var_decl_specifiers(
     string name: string ref
 )
 is_structured_binding(unique int id: @variable ref);
+var_requires(
+    unique int id: @var_decl ref,
+    int constraint: @expr ref
+);
 
 type_decls(
     unique int id: @type_decl,
@@ -511,6 +529,10 @@ type_def(unique int id: @type_decl ref);
 type_decl_top(
     unique int type_decl: @type_decl ref
 );
+type_requires(
+    unique int id: @type_decl ref,
+    int constraint: @expr ref
+);
 
 namespace_decls(
     unique int id: @namespace_decl,
@@ -790,6 +812,11 @@ nontype_template_parameters(
     int id: @expr ref
 );
 
+type_template_type_constraint(
+    unique int id: @usertype ref,
+    int constraint: @expr ref
+);
+
 mangled_name(
     unique int id: @declaration ref,
     int mangled_name : @mangledname,