Don't warn about unloaded crates (rust-lang/rust-clippy#14733)

Fixes
https://github.com/rust-lang/rust-clippy/pull/14397#issuecomment-2848328221

r? @samueltardieu

changelog: Don't warn about clippy.toml disallowed paths for crates that
were not loaded

4 files changed, 41 insertions, 4 deletions

diff --git a/src/tools/clippy/clippy_config/src/types.rs b/src/tools/clippy/clippy_config/src/types.rs
index 5949eaca7bc..70cf0915bb6 100644
--- a/src/tools/clippy/clippy_config/src/types.rs
+++ b/src/tools/clippy/clippy_config/src/types.rs
@@ -4,7 +4,7 @@ use rustc_hir::PrimTy;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefIdMap;
 use rustc_middle::ty::TyCtxt;
-use rustc_span::Span;
+use rustc_span::{Span, Symbol};
 use serde::de::{self, Deserializer, Visitor};
 use serde::{Deserialize, Serialize, ser};
 use std::collections::HashMap;
@@ -145,7 +145,8 @@ pub fn create_disallowed_map<const REPLACEMENT_ALLOWED: bool>(
         FxHashMap::default();
     for disallowed_path in disallowed_paths {
         let path = disallowed_path.path();
-        let mut resolutions = clippy_utils::def_path_res(tcx, &path.split("::").collect::<Vec<_>>());
+        let path_split = path.split("::").collect::<Vec<_>>();
+        let mut resolutions = clippy_utils::def_path_res(tcx, &path_split);
 
         let mut found_def_id = None;
         let mut found_prim_ty = false;
@@ -160,8 +161,12 @@ pub fn create_disallowed_map<const REPLACEMENT_ALLOWED: bool>(
             },
             _ => false,
         });
-
-        if resolutions.is_empty() {
+        if resolutions.is_empty()
+            // Don't warn about unloaded crates:
+            // https://github.com/rust-lang/rust-clippy/pull/14397#issuecomment-2848328221
+            && (path_split.len() < 2
+                || !clippy_utils::find_crates(tcx, Symbol::intern(path_split[0])).is_empty())
+        {
             let span = disallowed_path.span();
 
             if let Some(def_id) = found_def_id {
diff --git a/src/tools/clippy/tests/ui-toml/toml_unloaded_crate/clippy.toml b/src/tools/clippy/tests/ui-toml/toml_unloaded_crate/clippy.toml
new file mode 100644
index 00000000000..e664256d2a2
--- /dev/null
+++ b/src/tools/clippy/tests/ui-toml/toml_unloaded_crate/clippy.toml
@@ -0,0 +1,10 @@
+# The first two `disallowed-methods` paths should generate warnings, but the third should not.
+
+[[disallowed-methods]]
+path = "regex::Regex::new_"
+
+[[disallowed-methods]]
+path = "regex::Regex_::new"
+
+[[disallowed-methods]]
+path = "regex_::Regex::new"
diff --git a/src/tools/clippy/tests/ui-toml/toml_unloaded_crate/conf_unloaded_crate.rs b/src/tools/clippy/tests/ui-toml/toml_unloaded_crate/conf_unloaded_crate.rs
new file mode 100644
index 00000000000..2dbc5eca32e
--- /dev/null
+++ b/src/tools/clippy/tests/ui-toml/toml_unloaded_crate/conf_unloaded_crate.rs
@@ -0,0 +1,6 @@
+//@error-in-other-file: `regex::Regex::new_` does not refer to an existing function
+//@error-in-other-file: `regex::Regex_::new` does not refer to an existing function
+
+extern crate regex;
+
+fn main() {}
diff --git a/src/tools/clippy/tests/ui-toml/toml_unloaded_crate/conf_unloaded_crate.stderr b/src/tools/clippy/tests/ui-toml/toml_unloaded_crate/conf_unloaded_crate.stderr
new file mode 100644
index 00000000000..5d28e5fa970
--- /dev/null
+++ b/src/tools/clippy/tests/ui-toml/toml_unloaded_crate/conf_unloaded_crate.stderr
@@ -0,0 +1,16 @@
+warning: `regex::Regex::new_` does not refer to an existing function
+  --> $DIR/tests/ui-toml/toml_unloaded_crate/clippy.toml:3:1
+   |
+LL | / [[disallowed-methods]]
+LL | | path = "regex::Regex::new_"
+   | |___________________________^
+
+warning: `regex::Regex_::new` does not refer to an existing function
+  --> $DIR/tests/ui-toml/toml_unloaded_crate/clippy.toml:6:1
+   |
+LL | / [[disallowed-methods]]
+LL | | path = "regex::Regex_::new"
+   | |___________________________^
+
+warning: 2 warnings emitted
+