1 files changed, 108 insertions, 0 deletions
diff --git a/clippy_lints/src/utils/internal_lints/invalid_paths.rs b/clippy_lints/src/utils/internal_lints/invalid_paths.rs
new file mode 100644
index 00000000000..25532dd4e26
--- /dev/null
+++ b/clippy_lints/src/utils/internal_lints/invalid_paths.rs
@@ -0,0 +1,108 @@
+use clippy_utils::consts::{constant_simple, Constant};
+use clippy_utils::def_path_res;
+use clippy_utils::diagnostics::span_lint;
+use if_chain::if_chain;
+use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::Item;
+use rustc_hir_analysis::hir_ty_to_ty;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty::{self, fast_reject::SimplifiedTypeGen, FloatTy};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::symbol::Symbol;
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks the paths module for invalid paths.
+    ///
+    /// ### Why is this bad?
+    /// It indicates a bug in the code.
+    ///
+    /// ### Example
+    /// None.
+    pub INVALID_PATHS,
+    internal,
+    "invalid path"
+}
+
+declare_lint_pass!(InvalidPaths => [INVALID_PATHS]);
+
+impl<'tcx> LateLintPass<'tcx> for InvalidPaths {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
+        let local_def_id = &cx.tcx.parent_module(item.hir_id());
+        let mod_name = &cx.tcx.item_name(local_def_id.to_def_id());
+        if_chain! {
+            if mod_name.as_str() == "paths";
+            if let hir::ItemKind::Const(ty, body_id) = item.kind;
+            let ty = hir_ty_to_ty(cx.tcx, ty);
+            if let ty::Array(el_ty, _) = &ty.kind();
+            if let ty::Ref(_, el_ty, _) = &el_ty.kind();
+            if el_ty.is_str();
+            let body = cx.tcx.hir().body(body_id);
+            let typeck_results = cx.tcx.typeck_body(body_id);
+            if let Some(Constant::Vec(path)) = constant_simple(cx, typeck_results, body.value);
+            let path: Vec<&str> = path
+                .iter()
+                .map(|x| {
+                    if let Constant::Str(s) = x {
+                        s.as_str()
+                    } else {
+                        // We checked the type of the constant above
+                        unreachable!()
+                    }
+                })
+                .collect();
+            if !check_path(cx, &path[..]);
+            then {
+                span_lint(cx, INVALID_PATHS, item.span, "invalid path");
+            }
+        }
+    }
+}
+
+// This is not a complete resolver for paths. It works on all the paths currently used in the paths
+// module.  That's all it does and all it needs to do.
+pub fn check_path(cx: &LateContext<'_>, path: &[&str]) -> bool {
+    if def_path_res(cx, path, None) != Res::Err {
+        return true;
+    }
+
+    // Some implementations can't be found by `path_to_res`, particularly inherent
+    // implementations of native types. Check lang items.
+    let path_syms: Vec<_> = path.iter().map(|p| Symbol::intern(p)).collect();
+    let lang_items = cx.tcx.lang_items();
+    // This list isn't complete, but good enough for our current list of paths.
+    let incoherent_impls = [
+        SimplifiedTypeGen::FloatSimplifiedType(FloatTy::F32),
+        SimplifiedTypeGen::FloatSimplifiedType(FloatTy::F64),
+        SimplifiedTypeGen::SliceSimplifiedType,
+        SimplifiedTypeGen::StrSimplifiedType,
+    ]
+    .iter()
+    .flat_map(|&ty| cx.tcx.incoherent_impls(ty));
+    for item_def_id in lang_items.items().iter().flatten().chain(incoherent_impls) {
+        let lang_item_path = cx.get_def_path(*item_def_id);
+        if path_syms.starts_with(&lang_item_path) {
+            if let [item] = &path_syms[lang_item_path.len()..] {
+                if matches!(
+                    cx.tcx.def_kind(*item_def_id),
+                    DefKind::Mod | DefKind::Enum | DefKind::Trait
+                ) {
+                    for child in cx.tcx.module_children(*item_def_id) {
+                        if child.ident.name == *item {
+                            return true;
+                        }
+                    }
+                } else {
+                    for child in cx.tcx.associated_item_def_ids(*item_def_id) {
+                        if cx.tcx.item_name(*child) == *item {
+                            return true;
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    false
+}