C++: Give names in structured binding declarations correct IR types

cpp/ql/lib/semmle/code/cpp/ir/internal/IRUtilities.qll

@@ -11,6 +11,15 @@ private Type getDecayedType(Type type) {
   result.(PointerType).getBaseType() = type.(ArrayType).getBaseType()
 }
 
+/**
+ * Holds if the sepcified variable is a structured binding with a non-reference
+ * type.
+ */
+predicate isNonReferenceStructuredBinding(Variable v) {
+  v.isStructuredBinding() and
+  not v.getUnderlyingType() instanceof ReferenceType
+}
+
 /**
  * Get the actual type of the specified variable, as opposed to the declared type.
  * This returns the type of the variable after any pointer decay is applied, and
@@ -30,7 +39,10 @@ Type getVariableType(Variable v) {
         result = v.getInitializer().getExpr().getType()
         or
         not exists(v.getInitializer()) and result = v.getType()
-      else result = v.getType()
+      else
+        if isNonReferenceStructuredBinding(v)
+        then exists(ReferenceType r | r.getBaseType() = v.getUnderlyingType() | result = r)
+        else result = v.getType()
   )
 }