Auto merge of #6617 - Manishearth:exhaustive_enums, r=camsteffen

New lint: exhaustive_enums, exhaustive_structs

Fixes #6616

changelog: Added restriction lint: `exhaustive_enums`, `exhaustive_structs`

clippy_lints/src/exhaustive_items.rs

@@ -0,0 +1,102 @@
+use crate::utils::{indent_of, span_lint_and_then};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::{Item, ItemKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::sym;
+
+declare_clippy_lint! {
+    /// **What it does:** Warns on any exported `enum`s that are not tagged `#[non_exhaustive]`
+    ///
+    /// **Why is this bad?** Exhaustive enums are typically fine, but a project which does
+    /// not wish to make a stability commitment around exported enums may wish to
+    /// disable them by default.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    ///
+    /// ```rust
+    /// enum Foo {
+    ///     Bar,
+    ///     Baz
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// #[non_exhaustive]
+    /// enum Foo {
+    ///     Bar,
+    ///     Baz
+    /// }
+    /// ```
+    pub EXHAUSTIVE_ENUMS,
+    restriction,
+    "detects exported enums that have not been marked #[non_exhaustive]"
+}
+
+declare_clippy_lint! {
+    /// **What it does:** Warns on any exported `structs`s that are not tagged `#[non_exhaustive]`
+    ///
+    /// **Why is this bad?** Exhaustive structs are typically fine, but a project which does
+    /// not wish to make a stability commitment around exported structs may wish to
+    /// disable them by default.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    ///
+    /// ```rust
+    /// struct Foo {
+    ///     bar: u8,
+    ///     baz: String,
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// #[non_exhaustive]
+    /// struct Foo {
+    ///     bar: u8,
+    ///     baz: String,
+    /// }
+    /// ```
+    pub EXHAUSTIVE_STRUCTS,
+    restriction,
+    "detects exported structs that have not been marked #[non_exhaustive]"
+}
+
+declare_lint_pass!(ExhaustiveItems => [EXHAUSTIVE_ENUMS, EXHAUSTIVE_STRUCTS]);
+
+impl LateLintPass<'_> for ExhaustiveItems {
+    fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
+        if_chain! {
+            if let ItemKind::Enum(..) | ItemKind::Struct(..) = item.kind;
+            if cx.access_levels.is_exported(item.hir_id);
+            if !item.attrs.iter().any(|a| a.has_name(sym::non_exhaustive));
+            then {
+                let (lint, msg) = if let ItemKind::Enum(..) = item.kind {
+                    (EXHAUSTIVE_ENUMS, "exported enums should not be exhaustive")
+                } else {
+                    (EXHAUSTIVE_STRUCTS, "exported structs should not be exhaustive")
+                };
+                let suggestion_span = item.span.shrink_to_lo();
+                let indent = " ".repeat(indent_of(cx, item.span).unwrap_or(0));
+                span_lint_and_then(
+                    cx,
+                    lint,
+                    item.span,
+                    msg,
+                    |diag| {
+                        let sugg = format!("#[non_exhaustive]\n{}", indent);
+                        diag.span_suggestion(suggestion_span,
+                                             "try adding #[non_exhaustive]",
+                                             sugg,
+                                             Applicability::MaybeIncorrect);
+                    }
+                );
+
+            }
+        }
+    }
+}

clippy_lints/src/lib.rs

@@ -200,6 +200,7 @@ mod escape;
 mod eta_reduction;
 mod eval_order_dependence;
 mod excessive_bools;
+mod exhaustive_items;
 mod exit;
 mod explicit_write;
 mod fallible_impl_from;
@@ -615,6 +616,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         &eval_order_dependence::EVAL_ORDER_DEPENDENCE,
         &excessive_bools::FN_PARAMS_EXCESSIVE_BOOLS,
         &excessive_bools::STRUCT_EXCESSIVE_BOOLS,
+        &exhaustive_items::EXHAUSTIVE_ENUMS,
+        &exhaustive_items::EXHAUSTIVE_STRUCTS,
         &exit::EXIT,
         &explicit_write::EXPLICIT_WRITE,
         &fallible_impl_from::FALLIBLE_IMPL_FROM,
@@ -1101,6 +1104,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| box eval_order_dependence::EvalOrderDependence);
     store.register_late_pass(|| box missing_doc::MissingDoc::new());
     store.register_late_pass(|| box missing_inline::MissingInline);
+    store.register_late_pass(move || box exhaustive_items::ExhaustiveItems);
     store.register_late_pass(|| box if_let_some_result::OkIfLet);
     store.register_late_pass(|| box partialeq_ne_impl::PartialEqNeImpl);
     store.register_late_pass(|| box unused_io_amount::UnusedIoAmount);
@@ -1251,6 +1255,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&create_dir::CREATE_DIR),
         LintId::of(&dbg_macro::DBG_MACRO),
         LintId::of(&else_if_without_else::ELSE_IF_WITHOUT_ELSE),
+        LintId::of(&exhaustive_items::EXHAUSTIVE_ENUMS),
+        LintId::of(&exhaustive_items::EXHAUSTIVE_STRUCTS),
         LintId::of(&exit::EXIT),
         LintId::of(&float_literal::LOSSY_FLOAT_LITERAL),
         LintId::of(&implicit_return::IMPLICIT_RETURN),