Fully qualify Result in generated doctest code

Author: GuillaumeGomez

Diff for: src/librustdoc/doctest/make.rs

@@ -208,7 +208,7 @@ impl DocTestBuilder {
             let (main_pre, main_post) = if returns_result {
                 (
                     format!(
-                        "fn main() {{ {inner_attr}fn {inner_fn_name}() -> Result<(), impl core::fmt::Debug> {{\n",
+                        "fn main() {{ {inner_attr}fn {inner_fn_name}() -> core::result::Result<(), impl core::fmt::Debug> {{\n",
                     ),
                     format!("\n}} {inner_fn_name}().unwrap() }}"),
                 )

Diff for: src/librustdoc/doctest/tests.rs

@@ -316,7 +316,7 @@ let mut input = String::new();
 io::stdin().read_line(&mut input)?;
 Ok::<(), io:Error>(())";
     let expected = "#![allow(unused)]
-fn main() { fn _inner() -> Result<(), impl core::fmt::Debug> {
+fn main() { fn _inner() -> core::result::Result<(), impl core::fmt::Debug> {
 use std::io;
 let mut input = String::new();
 io::stdin().read_line(&mut input)?;