config/Block: add ThrowWithNested()

src/config/Block.cxx

@@ -26,6 +26,13 @@
 #include <assert.h>
 #include <stdlib.h>
 
+void
+BlockParam::ThrowWithNested() const
+{
+	std::throw_with_nested(FormatRuntimeError("Error in setting \"%s\" on line %i",
+						  name.c_str(), line));
+}
+
 int
 BlockParam::GetIntValue() const
 {

src/config/Block.hxx

@@ -51,6 +51,14 @@ struct BlockParam {
 	unsigned GetPositiveValue() const;
 
 	bool GetBoolValue() const;
+
+	/**
+	 * Call this method in a "catch" block to throw a nested
+	 * exception showing the location of this setting in the
+	 * configuration file.
+	 */
+	[[noreturn]]
+	void ThrowWithNested() const;
 };
 
 struct ConfigBlock {