Merge pull request #16069 from jketema/var-templ

C++: Add `VariableTemplateInstantiation` class

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

@@ -590,6 +590,33 @@ class TemplateVariable extends Variable {
   Variable getAnInstantiation() { result.isConstructedFrom(this) }
 }
 
+/**
+ * A variable that is an instantiation of a template. For example
+ * the instantiation `myTemplateVariable<int>` in the following code:
+ * ```
+ * template<class T>
+ * T myTemplateVariable;
+ *
+ * void caller(int i) {
+ *   myTemplateVariable<int> = i;
+ * }
+ * ```
+ */
+class VariableTemplateInstantiation extends Variable {
+  TemplateVariable tv;
+
+  VariableTemplateInstantiation() { tv.getAnInstantiation() = this }
+
+  override string getAPrimaryQlClass() { result = "VariableTemplateInstantiation" }
+
+  /**
+   * Gets the variable template from which this instantiation was instantiated.
+   *
+   * Example: For `int x<int>`, returns `T x`.
+   */
+  TemplateVariable getTemplate() { result = tv }
+}
+
 /**
  * A non-static local variable or parameter that is not part of an
  * uninstantiated template. Uninstantiated templates are purely syntax, and

cpp/ql/test/library-tests/ir/ir/PrintAST.expected

@@ -15605,7 +15605,7 @@ ir.cpp:
 # 1934|             Type = [ClassTemplateInstantiation,Struct] Bar2<int>
 # 1934|             ValueCategory = lvalue
 # 1935|     getStmt(2): [ReturnStmt] return ...
-# 1938| [GlobalVariable] char global_template<char>
+# 1938| [GlobalVariable,VariableTemplateInstantiation] char global_template<char>
 # 1938|   getInitializer(): [Initializer] initializer for global_template
 # 1938|     getExpr(): [Literal] 42
 # 1938|         Type = [IntType] int
@@ -15616,7 +15616,7 @@ ir.cpp:
 # 1938|         Type = [PlainCharType] char
 # 1938|         Value = [CStyleCast] 42
 # 1938|         ValueCategory = prvalue
-# 1938| [GlobalVariable] int global_template<int>
+# 1938| [GlobalVariable,VariableTemplateInstantiation] int global_template<int>
 # 1938|   getInitializer(): [Initializer] initializer for global_template
 # 1938|     getExpr(): [Literal] 42
 # 1938|         Type = [IntType] int