tests/ui: Add a directory for warnings, add a test

Author: pacak

src/tools/tidy/src/ui_tests.rs

@@ -18,7 +18,7 @@ const ENTRY_LIMIT: usize = 900;
 // FIXME: The following limits should be reduced eventually.
 
 const ISSUES_ENTRY_LIMIT: usize = 1750;
-const ROOT_ENTRY_LIMIT: usize = 859;
+const ROOT_ENTRY_LIMIT: usize = 860;
 
 const EXPECTED_TEST_FILE_EXTENSIONS: &[&str] = &[
     "rs",     // test source files

tests/ui/warnings/no-explicit-path-issue-122509.rs

@@ -0,0 +1,23 @@
+//@ build-pass
+//@ compile-flags: -C codegen-units=2 --emit asm
+
+fn one() -> usize {
+    1
+}
+
+pub mod a {
+    pub fn two() -> usize {
+        ::one() + ::one()
+    }
+}
+
+pub mod b {
+    pub fn three() -> usize {
+        ::one() + ::a::two()
+    }
+}
+
+fn main() {
+    a::two();
+    b::three();
+}