Auto merge of #6905 - ThibsG:fpSingleComponentPathImports5210, r=giraffate

Fix FP in `single_component_path_imports` lint

Fix FP in  `single_component_path_imports` lint when the import is reused with `self`, like in `use self::module`.

Fixes #5210

changelog: none

tests/ui/single_component_path_imports.fixed

@@ -19,3 +19,16 @@ fn main() {
     // False positive #5154, shouldn't trigger lint.
     m!();
 }
+
+mod hello_mod {
+    
+    #[allow(dead_code)]
+    fn hello_mod() {}
+}
+
+mod hi_mod {
+    use self::regex::{Regex, RegexSet};
+    use regex;
+    #[allow(dead_code)]
+    fn hi_mod() {}
+}

tests/ui/single_component_path_imports.rs

@@ -19,3 +19,16 @@ fn main() {
     // False positive #5154, shouldn't trigger lint.
     m!();
 }
+
+mod hello_mod {
+    use regex;
+    #[allow(dead_code)]
+    fn hello_mod() {}
+}
+
+mod hi_mod {
+    use self::regex::{Regex, RegexSet};
+    use regex;
+    #[allow(dead_code)]
+    fn hi_mod() {}
+}

tests/ui/single_component_path_imports.stderr

@@ -1,10 +1,16 @@
+error: this import is redundant
+  --> $DIR/single_component_path_imports.rs:24:5
+   |
+LL |     use regex;
+   |     ^^^^^^^^^^ help: remove it entirely
+   |
+   = note: `-D clippy::single-component-path-imports` implied by `-D warnings`
+
 error: this import is redundant
   --> $DIR/single_component_path_imports.rs:6:1
    |
 LL | use regex;
    | ^^^^^^^^^^ help: remove it entirely
-   |
-   = note: `-D clippy::single-component-path-imports` implied by `-D warnings`
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 

tests/ui/single_component_path_imports_nested_first.rs

@@ -0,0 +1,17 @@
+// edition:2018
+#![warn(clippy::single_component_path_imports)]
+#![allow(unused_imports)]
+
+use regex;
+use serde as edres;
+pub use serde;
+
+fn main() {
+    regex::Regex::new(r"^\d{4}-\d{2}-\d{2}$").unwrap();
+}
+
+mod root_nested_use_mod {
+    use {regex, serde};
+    #[allow(dead_code)]
+    fn root_nested_use_mod() {}
+}

tests/ui/single_component_path_imports_nested_first.stderr

@@ -0,0 +1,25 @@
+error: this import is redundant
+  --> $DIR/single_component_path_imports_nested_first.rs:14:10
+   |
+LL |     use {regex, serde};
+   |          ^^^^^
+   |
+   = note: `-D clippy::single-component-path-imports` implied by `-D warnings`
+   = help: remove this import
+
+error: this import is redundant
+  --> $DIR/single_component_path_imports_nested_first.rs:14:17
+   |
+LL |     use {regex, serde};
+   |                 ^^^^^
+   |
+   = help: remove this import
+
+error: this import is redundant
+  --> $DIR/single_component_path_imports_nested_first.rs:5:1
+   |
+LL | use regex;
+   | ^^^^^^^^^^ help: remove it entirely
+
+error: aborting due to 3 previous errors
+

tests/ui/single_component_path_imports_self_after.rs

@@ -0,0 +1,16 @@
+// edition:2018
+#![warn(clippy::single_component_path_imports)]
+#![allow(unused_imports)]
+
+use self::regex::{Regex as xeger, RegexSet as tesxeger};
+pub use self::{
+    regex::{Regex, RegexSet},
+    some_mod::SomeType,
+};
+use regex;
+
+mod some_mod {
+    pub struct SomeType;
+}
+
+fn main() {}

tests/ui/single_component_path_imports_self_before.rs

@@ -0,0 +1,17 @@
+// edition:2018
+#![warn(clippy::single_component_path_imports)]
+#![allow(unused_imports)]
+
+use regex;
+
+use self::regex::{Regex as xeger, RegexSet as tesxeger};
+pub use self::{
+    regex::{Regex, RegexSet},
+    some_mod::SomeType,
+};
+
+mod some_mod {
+    pub struct SomeType;
+}
+
+fn main() {}