Implement internal lint for MSRV lints

This internal lint checks if the `extract_msrv_attrs!` macro is used if
a lint has a MSRV. If not, it suggests to add this attribute to the lint
pass implementation.

10 files changed, 177 insertions, 1 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 5cc5530f874..4ea70429621 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -50,6 +50,7 @@ syn = { version = "1.0", features = ["full"] }
 futures = "0.3"
 parking_lot = "0.11.2"
 tokio = { version = "1", features = ["io-util"] }
+rustc-semver = "1.1"
 num_cpus = "1.13"
 
 [build-dependencies]
diff --git a/clippy_lints/src/lib.register_internal.rs b/clippy_lints/src/lib.register_internal.rs
index 7d4c7d2adb5..4778f4fdfa7 100644
--- a/clippy_lints/src/lib.register_internal.rs
+++ b/clippy_lints/src/lib.register_internal.rs
@@ -14,6 +14,7 @@ store.register_group(true, "clippy::internal", Some("clippy_internal"), vec![
     LintId::of(utils::internal_lints::LINT_WITHOUT_LINT_PASS),
     LintId::of(utils::internal_lints::MATCH_TYPE_ON_DIAGNOSTIC_ITEM),
     LintId::of(utils::internal_lints::MISSING_CLIPPY_VERSION_ATTRIBUTE),
+    LintId::of(utils::internal_lints::MISSING_MSRV_ATTR_IMPL),
     LintId::of(utils::internal_lints::OUTER_EXPN_EXPN_DATA),
     LintId::of(utils::internal_lints::PRODUCE_ICE),
     LintId::of(utils::internal_lints::UNNECESSARY_SYMBOL_STR),
diff --git a/clippy_lints/src/lib.register_lints.rs b/clippy_lints/src/lib.register_lints.rs
index 686482671b4..f9337114038 100644
--- a/clippy_lints/src/lib.register_lints.rs
+++ b/clippy_lints/src/lib.register_lints.rs
@@ -26,6 +26,8 @@ store.register_lints(&[
     #[cfg(feature = "internal")]
     utils::internal_lints::MISSING_CLIPPY_VERSION_ATTRIBUTE,
     #[cfg(feature = "internal")]
+    utils::internal_lints::MISSING_MSRV_ATTR_IMPL,
+    #[cfg(feature = "internal")]
     utils::internal_lints::OUTER_EXPN_EXPN_DATA,
     #[cfg(feature = "internal")]
     utils::internal_lints::PRODUCE_ICE,
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 230e2b2ccdf..24b67c12f06 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -505,6 +505,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         store.register_late_pass(|| Box::new(utils::internal_lints::LintWithoutLintPass::default()));
         store.register_late_pass(|| Box::new(utils::internal_lints::MatchTypeOnDiagItem));
         store.register_late_pass(|| Box::new(utils::internal_lints::OuterExpnDataPass));
+        store.register_late_pass(|| Box::new(utils::internal_lints::MsrvAttrImpl));
     }
 
     store.register_late_pass(|| Box::new(utils::author::Author));
diff --git a/clippy_lints/src/utils/internal_lints.rs b/clippy_lints/src/utils/internal_lints.rs
index 4433d5f5bf1..b3b241392fe 100644
--- a/clippy_lints/src/utils/internal_lints.rs
+++ b/clippy_lints/src/utils/internal_lints.rs
@@ -25,7 +25,7 @@ use rustc_hir::{
 use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::mir::interpret::ConstValue;
-use rustc_middle::ty;
+use rustc_middle::ty::{self, subst::GenericArgKind};
 use rustc_semver::RustcVersion;
 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
 use rustc_span::source_map::Spanned;
@@ -337,6 +337,15 @@ declare_clippy_lint! {
     "found clippy lint without `clippy::version` attribute"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Check that the `extract_msrv_attr!` macro is used, when a lint has a MSRV.
+    ///
+    pub MISSING_MSRV_ATTR_IMPL,
+    internal,
+    "checking if all necessary steps were taken when adding a MSRV to a lint"
+}
+
 declare_lint_pass!(ClippyLintsInternal => [CLIPPY_LINTS_INTERNAL]);
 
 impl EarlyLintPass for ClippyLintsInternal {
@@ -1314,3 +1323,46 @@ fn if_chain_local_span(cx: &LateContext<'_>, local: &Local<'_>, if_chain_span: S
         span.parent(),
     )
 }
+
+declare_lint_pass!(MsrvAttrImpl => [MISSING_MSRV_ATTR_IMPL]);
+
+impl LateLintPass<'_> for MsrvAttrImpl {
+    fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
+        if_chain! {
+            if let hir::ItemKind::Impl(hir::Impl {
+                of_trait: Some(lint_pass_trait_ref),
+                self_ty,
+                items,
+                ..
+            }) = &item.kind;
+            if let Some(lint_pass_trait_def_id) = lint_pass_trait_ref.trait_def_id();
+            let is_late_pass = match_def_path(cx, lint_pass_trait_def_id, &paths::LATE_LINT_PASS);
+            if is_late_pass || match_def_path(cx, lint_pass_trait_def_id, &paths::EARLY_LINT_PASS);
+            let self_ty = hir_ty_to_ty(cx.tcx, self_ty);
+            if let ty::Adt(self_ty_def, _) = self_ty.kind();
+            if self_ty_def.is_struct();
+            if self_ty_def.all_fields().any(|f| {
+                cx.tcx
+                    .type_of(f.did)
+                    .walk()
+                    .filter(|t| matches!(t.unpack(), GenericArgKind::Type(_)))
+                    .any(|t| match_type(cx, t.expect_ty(), &paths::RUSTC_VERSION))
+            });
+            if !items.iter().any(|item| item.ident.name == sym!(enter_lint_attrs));
+            then {
+                let context = if is_late_pass { "LateContext" } else { "EarlyContext" };
+                let lint_pass = if is_late_pass { "LateLintPass" } else { "EarlyLintPass" };
+                let span = cx.sess().source_map().span_through_char(item.span, '{');
+                span_lint_and_sugg(
+                    cx,
+                    MISSING_MSRV_ATTR_IMPL,
+                    span,
+                    &format!("`extract_msrv_attr!` macro missing from `{lint_pass}` implementation"),
+                    &format!("add `extract_msrv_attr!({context})` to the `{lint_pass}` implementation"),
+                    format!("{}\n    extract_msrv_attr!({context});", snippet(cx, span, "..")),
+                    Applicability::MachineApplicable,
+                );
+            }
+        }
+    }
+}
diff --git a/clippy_utils/src/paths.rs b/clippy_utils/src/paths.rs
index 2778e30388e..6f56f8d5136 100644
--- a/clippy_utils/src/paths.rs
+++ b/clippy_utils/src/paths.rs
@@ -32,6 +32,8 @@ pub const DIR_BUILDER: [&str; 3] = ["std", "fs", "DirBuilder"];
 pub const DISPLAY_TRAIT: [&str; 3] = ["core", "fmt", "Display"];
 #[cfg(feature = "internal")]
 pub const EARLY_CONTEXT: [&str; 2] = ["rustc_lint", "EarlyContext"];
+#[cfg(feature = "internal")]
+pub const EARLY_LINT_PASS: [&str; 3] = ["rustc_lint", "passes", "EarlyLintPass"];
 pub const EXIT: [&str; 3] = ["std", "process", "exit"];
 pub const F32_EPSILON: [&str; 4] = ["core", "f32", "<impl f32>", "EPSILON"];
 pub const F64_EPSILON: [&str; 4] = ["core", "f64", "<impl f64>", "EPSILON"];
@@ -67,6 +69,8 @@ pub const KW_MODULE: [&str; 3] = ["rustc_span", "symbol", "kw"];
 #[cfg(feature = "internal")]
 pub const LATE_CONTEXT: [&str; 2] = ["rustc_lint", "LateContext"];
 #[cfg(feature = "internal")]
+pub const LATE_LINT_PASS: [&str; 3] = ["rustc_lint", "passes", "LateLintPass"];
+#[cfg(feature = "internal")]
 pub const LINT: [&str; 2] = ["rustc_lint_defs", "Lint"];
 pub const MUTEX_GUARD: [&str; 4] = ["std", "sync", "mutex", "MutexGuard"];
 pub const OPEN_OPTIONS: [&str; 3] = ["std", "fs", "OpenOptions"];
@@ -126,6 +130,8 @@ pub const REGEX_SET_NEW: [&str; 5] = ["regex", "re_set", "unicode", "RegexSet",
 pub const RESULT: [&str; 3] = ["core", "result", "Result"];
 pub const RESULT_ERR: [&str; 4] = ["core", "result", "Result", "Err"];
 pub const RESULT_OK: [&str; 4] = ["core", "result", "Result", "Ok"];
+#[cfg(feature = "internal")]
+pub const RUSTC_VERSION: [&str; 2] = ["rustc_semver", "RustcVersion"];
 pub const RWLOCK_READ_GUARD: [&str; 4] = ["std", "sync", "rwlock", "RwLockReadGuard"];
 pub const RWLOCK_WRITE_GUARD: [&str; 4] = ["std", "sync", "rwlock", "RwLockWriteGuard"];
 pub const SERDE_DESERIALIZE: [&str; 3] = ["serde", "de", "Deserialize"];
diff --git a/tests/compile-test.rs b/tests/compile-test.rs
index 6bc74bc1e9a..fc441e60802 100644
--- a/tests/compile-test.rs
+++ b/tests/compile-test.rs
@@ -34,6 +34,7 @@ static TEST_DEPENDENCIES: &[&str] = &[
     "syn",
     "tokio",
     "parking_lot",
+    "rustc_semver",
 ];
 
 // Test dependencies may need an `extern crate` here to ensure that they show up
@@ -53,6 +54,8 @@ extern crate parking_lot;
 #[allow(unused_extern_crates)]
 extern crate quote;
 #[allow(unused_extern_crates)]
+extern crate rustc_semver;
+#[allow(unused_extern_crates)]
 extern crate syn;
 #[allow(unused_extern_crates)]
 extern crate tokio;
diff --git a/tests/ui-internal/invalid_msrv_attr_impl.fixed b/tests/ui-internal/invalid_msrv_attr_impl.fixed
new file mode 100644
index 00000000000..900a8fffd40
--- /dev/null
+++ b/tests/ui-internal/invalid_msrv_attr_impl.fixed
@@ -0,0 +1,40 @@
+// run-rustfix
+
+#![deny(clippy::internal)]
+#![allow(clippy::missing_clippy_version_attribute)]
+#![feature(rustc_private)]
+
+extern crate rustc_ast;
+extern crate rustc_hir;
+extern crate rustc_lint;
+extern crate rustc_middle;
+#[macro_use]
+extern crate rustc_session;
+use clippy_utils::extract_msrv_attr;
+use rustc_hir::Expr;
+use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass};
+use rustc_semver::RustcVersion;
+
+declare_lint! {
+    pub TEST_LINT,
+    Warn,
+    ""
+}
+
+struct Pass {
+    msrv: Option<RustcVersion>,
+}
+
+impl_lint_pass!(Pass => [TEST_LINT]);
+
+impl LateLintPass<'_> for Pass {
+    extract_msrv_attr!(LateContext);
+    fn check_expr(&mut self, _: &LateContext<'_>, _: &Expr<'_>) {}
+}
+
+impl EarlyLintPass for Pass {
+    extract_msrv_attr!(EarlyContext);
+    fn check_expr(&mut self, _: &EarlyContext<'_>, _: &rustc_ast::Expr) {}
+}
+
+fn main() {}
diff --git a/tests/ui-internal/invalid_msrv_attr_impl.rs b/tests/ui-internal/invalid_msrv_attr_impl.rs
new file mode 100644
index 00000000000..4bc8164db67
--- /dev/null
+++ b/tests/ui-internal/invalid_msrv_attr_impl.rs
@@ -0,0 +1,38 @@
+// run-rustfix
+
+#![deny(clippy::internal)]
+#![allow(clippy::missing_clippy_version_attribute)]
+#![feature(rustc_private)]
+
+extern crate rustc_ast;
+extern crate rustc_hir;
+extern crate rustc_lint;
+extern crate rustc_middle;
+#[macro_use]
+extern crate rustc_session;
+use clippy_utils::extract_msrv_attr;
+use rustc_hir::Expr;
+use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass};
+use rustc_semver::RustcVersion;
+
+declare_lint! {
+    pub TEST_LINT,
+    Warn,
+    ""
+}
+
+struct Pass {
+    msrv: Option<RustcVersion>,
+}
+
+impl_lint_pass!(Pass => [TEST_LINT]);
+
+impl LateLintPass<'_> for Pass {
+    fn check_expr(&mut self, _: &LateContext<'_>, _: &Expr<'_>) {}
+}
+
+impl EarlyLintPass for Pass {
+    fn check_expr(&mut self, _: &EarlyContext<'_>, _: &rustc_ast::Expr) {}
+}
+
+fn main() {}
diff --git a/tests/ui-internal/invalid_msrv_attr_impl.stderr b/tests/ui-internal/invalid_msrv_attr_impl.stderr
new file mode 100644
index 00000000000..ddc06f0be1b
--- /dev/null
+++ b/tests/ui-internal/invalid_msrv_attr_impl.stderr
@@ -0,0 +1,32 @@
+error: `extract_msrv_attr!` macro missing from `LateLintPass` implementation
+  --> $DIR/invalid_msrv_attr_impl.rs:30:1
+   |
+LL | impl LateLintPass<'_> for Pass {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/invalid_msrv_attr_impl.rs:3:9
+   |
+LL | #![deny(clippy::internal)]
+   |         ^^^^^^^^^^^^^^^^
+   = note: `#[deny(clippy::missing_msrv_attr_impl)]` implied by `#[deny(clippy::internal)]`
+help: add `extract_msrv_attr!(LateContext)` to the `LateLintPass` implementation
+   |
+LL + impl LateLintPass<'_> for Pass {
+LL +     extract_msrv_attr!(LateContext);
+   |
+
+error: `extract_msrv_attr!` macro missing from `EarlyLintPass` implementation
+  --> $DIR/invalid_msrv_attr_impl.rs:34:1
+   |
+LL | impl EarlyLintPass for Pass {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: add `extract_msrv_attr!(EarlyContext)` to the `EarlyLintPass` implementation
+   |
+LL + impl EarlyLintPass for Pass {
+LL +     extract_msrv_attr!(EarlyContext);
+   |
+
+error: aborting due to 2 previous errors
+