Reduce merged doctest source code size

Author: GuillaumeGomez

Diff for: test/src/types.rs

@@ -250,3 +250,37 @@ pub struct TestDescAndFn {
     pub desc: TestDesc,
     pub testfn: TestFn,
 }
+
+impl TestDescAndFn {
+    pub const fn new_doctest(
+        test_name: &'static str,
+        ignore: bool,
+        source_file: &'static str,
+        start_line: usize,
+        no_run: bool,
+        should_panic: bool,
+        testfn: TestFn,
+    ) -> Self {
+        Self {
+            desc: TestDesc {
+                name: StaticTestName(test_name),
+                ignore,
+                ignore_message: None,
+                source_file,
+                start_line,
+                start_col: 0,
+                end_line: 0,
+                end_col: 0,
+                compile_fail: false,
+                no_run,
+                should_panic: if should_panic {
+                    options::ShouldPanic::Yes
+                } else {
+                    options::ShouldPanic::No
+                },
+                test_type: TestType::DocTest,
+            },
+            testfn,
+        }
+    }
+}