add [assert_ok] lint

Signed-off-by: tabokie <[email protected]>

Author: tabokie

CHANGELOG.md

@@ -3439,6 +3439,7 @@ Released 2018-09-13
 [`approx_constant`]: https://rust-lang.github.io/rust-clippy/master/index.html#approx_constant
 [`as_conversions`]: https://rust-lang.github.io/rust-clippy/master/index.html#as_conversions
 [`as_underscore`]: https://rust-lang.github.io/rust-clippy/master/index.html#as_underscore
+[`assert_ok`]: https://rust-lang.github.io/rust-clippy/master/index.html#assert_ok
 [`assertions_on_constants`]: https://rust-lang.github.io/rust-clippy/master/index.html#assertions_on_constants
 [`assign_op_pattern`]: https://rust-lang.github.io/rust-clippy/master/index.html#assign_op_pattern
 [`assign_ops`]: https://rust-lang.github.io/rust-clippy/master/index.html#assign_ops

clippy_lints/src/assert_ok.rs

@@ -0,0 +1,64 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::macros::{find_assert_args, root_macro_call_first_node, PanicExpn};
+use clippy_utils::source::snippet_opt;
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::sym;
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for `assert!(r.is_ok())` calls.
+    ///
+    /// ### Why is this bad?
+    /// An assertion failure cannot output a useful message of the error.
+    ///
+    /// ### Known problems
+    /// The error type needs to implement `Debug`.
+    ///
+    /// ### Example
+    /// ```rust,ignore
+    /// # let r = Ok::<_, ()>(());
+    /// assert!(r.is_ok());
+    /// ```
+    #[clippy::version = "1.64.0"]
+    pub ASSERT_OK,
+    style,
+    "`assert!(r.is_ok())` gives worse error message than directly calling `r.unwrap()`"
+}
+
+declare_lint_pass!(AssertOk => [ASSERT_OK]);
+
+impl<'tcx> LateLintPass<'tcx> for AssertOk {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
+        if_chain! {
+            if let Some(macro_call) = root_macro_call_first_node(cx, e);
+            if matches!(cx.tcx.get_diagnostic_name(macro_call.def_id), Some(sym::assert_macro));
+            if let Some((condition, panic_expn)) = find_assert_args(cx, e, macro_call.expn);
+            if matches!(panic_expn, PanicExpn::Empty);
+            if let ExprKind::MethodCall(method_segment, args, _) = condition.kind;
+            if method_segment.ident.name == sym!(is_ok);
+            let method_receiver = &args[0];
+            if let Some(method_receiver_snippet) = snippet_opt(cx, method_receiver.span);
+            then {
+                span_lint_and_sugg(
+                    cx,
+                    ASSERT_OK,
+                    macro_call.span,
+                    &format!(
+                        "`assert!({}.is_ok())` gives bad error message",
+                        method_receiver_snippet
+                    ),
+                    "replace with",
+                    format!(
+                        "{}.unwrap()",
+                        method_receiver_snippet
+                    ),
+                    Applicability::Unspecified,
+                );
+            }
+        }
+    }
+}

clippy_lints/src/lib.register_all.rs

@@ -5,6 +5,7 @@
 store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(almost_complete_letter_range::ALMOST_COMPLETE_LETTER_RANGE),
     LintId::of(approx_const::APPROX_CONSTANT),
+    LintId::of(assert_ok::ASSERT_OK),
     LintId::of(assertions_on_constants::ASSERTIONS_ON_CONSTANTS),
     LintId::of(async_yields_async::ASYNC_YIELDS_ASYNC),
     LintId::of(attrs::BLANKET_CLIPPY_RESTRICTION_LINTS),

clippy_lints/src/lib.register_lints.rs

@@ -41,6 +41,7 @@ store.register_lints(&[
     as_underscore::AS_UNDERSCORE,
     asm_syntax::INLINE_ASM_X86_ATT_SYNTAX,
     asm_syntax::INLINE_ASM_X86_INTEL_SYNTAX,
+    assert_ok::ASSERT_OK,
     assertions_on_constants::ASSERTIONS_ON_CONSTANTS,
     async_yields_async::ASYNC_YIELDS_ASYNC,
     attrs::ALLOW_ATTRIBUTES_WITHOUT_REASON,

clippy_lints/src/lib.register_style.rs

@@ -3,6 +3,7 @@
 // Manual edits will be overwritten.
 
 store.register_group(true, "clippy::style", Some("clippy_style"), vec![
+    LintId::of(assert_ok::ASSERT_OK),
     LintId::of(assertions_on_constants::ASSERTIONS_ON_CONSTANTS),
     LintId::of(blacklisted_name::BLACKLISTED_NAME),
     LintId::of(blocks_in_if_conditions::BLOCKS_IN_IF_CONDITIONS),

clippy_lints/src/lib.rs

@@ -173,6 +173,7 @@ mod approx_const;
 mod as_conversions;
 mod as_underscore;
 mod asm_syntax;
+mod assert_ok;
 mod assertions_on_constants;
 mod async_yields_async;
 mod attrs;
@@ -726,6 +727,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| Box::new(slow_vector_initialization::SlowVectorInit));
     store.register_late_pass(|| Box::new(unnecessary_sort_by::UnnecessarySortBy));
     store.register_late_pass(move || Box::new(unnecessary_wraps::UnnecessaryWraps::new(avoid_breaking_exported_api)));
+    store.register_late_pass(|| Box::new(assert_ok::AssertOk));
     store.register_late_pass(|| Box::new(assertions_on_constants::AssertionsOnConstants));
     store.register_late_pass(|| Box::new(transmuting_null::TransmutingNull));
     store.register_late_pass(|| Box::new(path_buf_push_overwrite::PathBufPushOverwrite));

tests/ui/assert_ok.fixed

@@ -0,0 +1,8 @@
+// run-rustfix
+#![warn(clippy::assert_ok)]
+
+fn main() {
+    // basic case
+    let r: std::result::Result<(), ()> = Ok(());
+    r.unwrap();
+}

tests/ui/assert_ok.rs

@@ -0,0 +1,8 @@
+// run-rustfix
+#![warn(clippy::assert_ok)]
+
+fn main() {
+    // basic case
+    let r: std::result::Result<(), ()> = Ok(());
+    assert!(r.is_ok());
+}

tests/ui/assert_ok.stderr

@@ -0,0 +1,10 @@
+error: `assert!(r.is_ok())` gives bad error message
+  --> $DIR/assert_ok.rs:7:5
+   |
+LL |     assert!(r.is_ok());
+   |     ^^^^^^^^^^^^^^^^^^ help: replace with: `r.unwrap()`
+   |
+   = note: `-D clippy::assert-ok` implied by `-D warnings`
+
+error: aborting due to previous error
+