Improve filtering and account for spacing

Author: blyxyas

clippy_lints/src/doc/needless_doctest_main.rs

@@ -134,7 +134,8 @@ pub fn check(
     //
     // Also, as we only check for attribute names and don't do macro expansion,
     // we can check only for #[test]
-    if !(text.contains("fn main") || text.contains("#[test]")) {
+
+    if !((text.contains(" main") && text.splitn(2, "fn ").nth(2).is_none()) || text.contains("#[test]")) {
         return;
     }
 

tests/ui/doc/needless_doctest_main.rs

@@ -82,4 +82,14 @@ fn lumpimupli() {}
 /// ```
 fn mpulpilumi() {}
 
+#[rustfmt::skip]
+/// Spaces in weird positions
+/// ```rust
+/// fn     main   (){
+//~^ error: needless `fn main` in doctest
+///     let _ = 0;
+/// }
+/// ```
+fn plumpiplupi() {}
+
 fn main() {}

tests/ui/doc/needless_doctest_main.stderr

@@ -22,5 +22,15 @@ LL | | ///     let _ = 0;
 LL | | /// }
    | |_____^
 
-error: aborting due to 2 previous errors
+error: needless `fn main` in doctest
+  --> tests/ui/doc/needless_doctest_main.rs:88:5
+   |
+LL |   /// fn     main   (){
+   |  _____^
+LL | |
+LL | | ///     let _ = 0;
+LL | | /// }
+   | |_____^
+
+error: aborting due to 3 previous errors