Rollup merge of #79775 - jyn514:doctest, r=GuillaumeGomez

Fix injected errors when running doctests on a crate named after a keyword

Closes #79771

Author: Dylan-DPC

src/librustdoc/doctest.rs

@@ -546,9 +546,12 @@ crate fn make_test(
     // compiler.
     if !already_has_extern_crate && !opts.no_crate_inject && cratename != Some("std") {
         if let Some(cratename) = cratename {
-            // Make sure its actually used if not included.
+            // Don't inject `extern crate` if the crate is never used.
+            // NOTE: this is terribly inaccurate because it doesn't actually
+            // parse the source, but only has false positives, not false
+            // negatives.
             if s.contains(cratename) {
-                prog.push_str(&format!("extern crate {};\n", cratename));
+                prog.push_str(&format!("extern crate r#{};\n", cratename));
                 line_offset += 1;
             }
         }

src/librustdoc/doctest/tests.rs

@@ -38,7 +38,7 @@ fn make_test_crate_name() {
     let input = "use asdf::qwop;
 assert_eq!(2+2, 4);";
     let expected = "#![allow(unused)]
-extern crate asdf;
+extern crate r#asdf;
 fn main() {
 use asdf::qwop;
 assert_eq!(2+2, 4);
@@ -128,7 +128,7 @@ fn make_test_opts_attrs() {
     let input = "use asdf::qwop;
 assert_eq!(2+2, 4);";
     let expected = "#![feature(sick_rad)]
-extern crate asdf;
+extern crate r#asdf;
 fn main() {
 use asdf::qwop;
 assert_eq!(2+2, 4);
@@ -141,7 +141,7 @@ assert_eq!(2+2, 4);
     opts.attrs.push("feature(hella_dope)".to_string());
     let expected = "#![feature(sick_rad)]
 #![feature(hella_dope)]
-extern crate asdf;
+extern crate r#asdf;
 fn main() {
 use asdf::qwop;
 assert_eq!(2+2, 4);
@@ -250,7 +250,7 @@ assert_eq!(asdf::foo, 4);";
 
     let expected = "#![allow(unused)]
 extern crate hella_qwop;
-extern crate asdf;
+extern crate r#asdf;
 fn main() {
 assert_eq!(asdf::foo, 4);
 }"

src/test/rustdoc/playground-arg.rs

@@ -11,4 +11,4 @@
 pub fn dummy() {}
 
 // ensure that `extern crate foo;` was inserted into code snips automatically:
-// @matches foo/index.html '//a[@class="test-arrow"][@href="https://example.com/?code=%23!%5Ballow(unused)%5D%0Aextern%20crate%20foo%3B%0Afn%20main()%20%7B%0Ause%20foo%3A%3Adummy%3B%0Adummy()%3B%0A%7D&edition=2015"]' "Run"
+// @matches foo/index.html '//a[@class="test-arrow"][@href="https://example.com/?code=%23!%5Ballow(unused)%5D%0Aextern%20crate%20r%23foo%3B%0Afn%20main()%20%7B%0Ause%20foo%3A%3Adummy%3B%0Adummy()%3B%0A%7D&edition=2015"]' "Run"