added restriction lint that prohibits the usage of unimplemented, unreachable or panic in a function of type result or option

Author: Vali Schneider

CHANGELOG.md

@@ -1651,6 +1651,7 @@ Released 2018-09-13
 [`out_of_bounds_indexing`]: https://rust-lang.github.io/rust-clippy/master/index.html#out_of_bounds_indexing
 [`overflow_check_conditional`]: https://rust-lang.github.io/rust-clippy/master/index.html#overflow_check_conditional
 [`panic`]: https://rust-lang.github.io/rust-clippy/master/index.html#panic
+[`panic_in_result`]: https://rust-lang.github.io/rust-clippy/master/index.html#panic_in_result
 [`panic_params`]: https://rust-lang.github.io/rust-clippy/master/index.html#panic_params
 [`panicking_unwrap`]: https://rust-lang.github.io/rust-clippy/master/index.html#panicking_unwrap
 [`partialeq_ne_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#partialeq_ne_impl

clippy_lints/src/lib.rs

@@ -267,6 +267,7 @@ mod open_options;
 mod option_env_unwrap;
 mod option_if_let_else;
 mod overflow_check_conditional;
+mod panic_in_result;
 mod panic_unimplemented;
 mod partialeq_ne_impl;
 mod path_buf_push_overwrite;
@@ -747,6 +748,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         &option_env_unwrap::OPTION_ENV_UNWRAP,
         &option_if_let_else::OPTION_IF_LET_ELSE,
         &overflow_check_conditional::OVERFLOW_CHECK_CONDITIONAL,
+        &panic_in_result::PANIC_IN_RESULT,
         &panic_unimplemented::PANIC,
         &panic_unimplemented::PANIC_PARAMS,
         &panic_unimplemented::TODO,
@@ -1086,6 +1088,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| box manual_async_fn::ManualAsyncFn);
     store.register_early_pass(|| box redundant_field_names::RedundantFieldNames);
     store.register_late_pass(|| box vec_resize_to_zero::VecResizeToZero);
+    store.register_late_pass(|| box panic_in_result::PanicInResult);
+
     let single_char_binding_names_threshold = conf.single_char_binding_names_threshold;
     store.register_early_pass(move || box non_expressive_names::NonExpressiveNames {
         single_char_binding_names_threshold,
@@ -1128,6 +1132,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&missing_doc::MISSING_DOCS_IN_PRIVATE_ITEMS),
         LintId::of(&missing_inline::MISSING_INLINE_IN_PUBLIC_ITEMS),
         LintId::of(&modulo_arithmetic::MODULO_ARITHMETIC),
+        LintId::of(&panic_in_result::PANIC_IN_RESULT),
         LintId::of(&panic_unimplemented::PANIC),
         LintId::of(&panic_unimplemented::TODO),
         LintId::of(&panic_unimplemented::UNIMPLEMENTED),

clippy_lints/src/panic_in_result.rs

@@ -0,0 +1,100 @@
+use crate::utils::{is_expn_of, is_type_diagnostic_item, return_ty, span_lint_and_then};
+use if_chain::if_chain;
+use rustc_hir as hir;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::hir::map::Map;
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::Span;
+
+declare_clippy_lint! {
+    /// **What it does:** Checks for usage of `panic!`, `unimplemented!` or `unreachable!` in a function of type result/option.
+    ///
+    /// **Why is this bad?** For some codebases,
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    ///
+    /// ```rust
+    /// fn option_with_panic() -> Option<bool> // should emit lint
+    /// {
+    ///     panic!("error");
+    /// }
+    /// ```
+
+    pub PANIC_IN_RESULT,
+    restriction,
+    "functions of type `Result<..>` / `Option`<...> that contain `panic!()` or `unreachable()` or `unimplemented()` "
+}
+
+declare_lint_pass!(PanicInResult => [PANIC_IN_RESULT]);
+
+impl<'tcx> LateLintPass<'tcx> for PanicInResult {
+    fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
+        if_chain! {
+            // first check if it's a method or function
+            if let hir::ImplItemKind::Fn(ref _signature, _) = impl_item.kind;
+            // checking if its return type is `result` or `option`
+            if is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id), sym!(result_type))
+                || is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id), sym!(option_type));
+            then {
+                lint_impl_body(cx, impl_item.span, impl_item);
+            }
+        }
+    }
+}
+
+use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc_hir::{Expr, ImplItemKind};
+
+struct FindPanicUnimplementedUnreachable {
+    result: Vec<Span>,
+}
+
+impl<'tcx> Visitor<'tcx> for FindPanicUnimplementedUnreachable {
+    type Map = Map<'tcx>;
+
+    fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
+        if is_expn_of(expr.span, "unimplemented").is_some() {
+            self.result.push(expr.span);
+        } else if is_expn_of(expr.span, "unreachable").is_some() {
+            self.result.push(expr.span);
+        } else if is_expn_of(expr.span, "panic").is_some() {
+            self.result.push(expr.span);
+        }
+
+        // and check sub-expressions
+        intravisit::walk_expr(self, expr);
+    }
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+        NestedVisitorMap::None
+    }
+}
+
+fn lint_impl_body<'tcx>(cx: &LateContext<'tcx>, impl_span: Span, impl_item: &'tcx hir::ImplItem<'_>) {
+    if_chain! {
+        if let ImplItemKind::Fn(_, body_id) = impl_item.kind;
+        then {
+            let body = cx.tcx.hir().body(body_id);
+            let mut fpu = FindPanicUnimplementedUnreachable {
+                result: Vec::new(),
+            };
+            fpu.visit_expr(&body.value);
+
+            // if we've found one, lint
+            if  !fpu.result.is_empty()  {
+                span_lint_and_then(
+                    cx,
+                    PANIC_IN_RESULT,
+                    impl_span,
+                    "used unimplemented, unreachable or panic in a function that returns result or option",
+                    move |diag| {
+                        diag.help(
+                            "unimplemented, unreachable or panic should not be used in a function that returns result or option" );
+                        diag.span_note(fpu.result, "will cause the application to crash.");
+                    });
+            }
+        }
+    }
+}

src/lintlist/mod.rs

@@ -1704,6 +1704,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
         deprecation: None,
         module: "panic_unimplemented",
     },
+    Lint {
+        name: "panic_in_result",
+        group: "restriction",
+        desc: "default lint description",
+        deprecation: None,
+        module: "panic_in_result",
+    },
     Lint {
         name: "panic_params",
         group: "style",

tests/ui/panic_in_result.rs

@@ -0,0 +1,62 @@
+#![warn(clippy::panic_in_result)]
+
+struct A;
+
+impl A {
+    fn result_with_panic() -> Result<bool, String> // should emit lint
+    {
+        panic!("error");
+    }
+
+    fn result_with_unimplemented() -> Result<bool, String> // should emit lint
+    {
+        unimplemented!();
+    }
+
+    fn result_with_unreachable() -> Result<bool, String> // should emit lint
+    {
+        unreachable!();
+    }
+
+    fn option_with_unreachable() -> Option<bool> // should emit lint
+    {
+        unreachable!();
+    }
+
+    fn option_with_unimplemented() -> Option<bool> // should emit lint
+    {
+        unimplemented!();
+    }
+
+    fn option_with_panic() -> Option<bool> // should emit lint
+    {
+        panic!("error");
+    }
+
+    fn other_with_panic() // should not emit lint
+    {
+        panic!("");
+    }
+
+    fn other_with_unreachable() // should not emit lint
+    {
+        unreachable!();
+    }
+
+    fn other_with_unimplemented() // should not emit lint
+    {
+        unimplemented!();
+    }
+
+    fn result_without_banned_functions() -> Result<bool, String> // should not emit lint
+    {
+        Ok(true)
+    }
+
+    fn option_without_banned_functions() -> Option<bool> // should not emit lint
+    {
+        Some(true)
+    }
+}
+
+fn main() {}

tests/ui/panic_in_result.stderr

@@ -0,0 +1,105 @@
+error: used unimplemented, unreachable or panic in a function that returns result or option
+  --> $DIR/panic_in_result.rs:6:5
+   |
+LL | /     fn result_with_panic() -> Result<bool, String> // should emit lint
+LL | |     {
+LL | |         panic!("error");
+LL | |     }
+   | |_____^
+   |
+   = note: `-D clippy::panic-in-result` implied by `-D warnings`
+   = help: unimplemented, unreachable or panic should not be used in a function that returns result or option
+note: will cause the application to crash.
+  --> $DIR/panic_in_result.rs:8:9
+   |
+LL |         panic!("error");
+   |         ^^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: used unimplemented, unreachable or panic in a function that returns result or option
+  --> $DIR/panic_in_result.rs:11:5
+   |
+LL | /     fn result_with_unimplemented() -> Result<bool, String> // should emit lint
+LL | |     {
+LL | |         unimplemented!();
+LL | |     }
+   | |_____^
+   |
+   = help: unimplemented, unreachable or panic should not be used in a function that returns result or option
+note: will cause the application to crash.
+  --> $DIR/panic_in_result.rs:13:9
+   |
+LL |         unimplemented!();
+   |         ^^^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: used unimplemented, unreachable or panic in a function that returns result or option
+  --> $DIR/panic_in_result.rs:16:5
+   |
+LL | /     fn result_with_unreachable() -> Result<bool, String> // should emit lint
+LL | |     {
+LL | |         unreachable!();
+LL | |     }
+   | |_____^
+   |
+   = help: unimplemented, unreachable or panic should not be used in a function that returns result or option
+note: will cause the application to crash.
+  --> $DIR/panic_in_result.rs:18:9
+   |
+LL |         unreachable!();
+   |         ^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: used unimplemented, unreachable or panic in a function that returns result or option
+  --> $DIR/panic_in_result.rs:21:5
+   |
+LL | /     fn option_with_unreachable() -> Option<bool> // should emit lint
+LL | |     {
+LL | |         unreachable!();
+LL | |     }
+   | |_____^
+   |
+   = help: unimplemented, unreachable or panic should not be used in a function that returns result or option
+note: will cause the application to crash.
+  --> $DIR/panic_in_result.rs:23:9
+   |
+LL |         unreachable!();
+   |         ^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: used unimplemented, unreachable or panic in a function that returns result or option
+  --> $DIR/panic_in_result.rs:26:5
+   |
+LL | /     fn option_with_unimplemented() -> Option<bool> // should emit lint
+LL | |     {
+LL | |         unimplemented!();
+LL | |     }
+   | |_____^
+   |
+   = help: unimplemented, unreachable or panic should not be used in a function that returns result or option
+note: will cause the application to crash.
+  --> $DIR/panic_in_result.rs:28:9
+   |
+LL |         unimplemented!();
+   |         ^^^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: used unimplemented, unreachable or panic in a function that returns result or option
+  --> $DIR/panic_in_result.rs:31:5
+   |
+LL | /     fn option_with_panic() -> Option<bool> // should emit lint
+LL | |     {
+LL | |         panic!("error");
+LL | |     }
+   | |_____^
+   |
+   = help: unimplemented, unreachable or panic should not be used in a function that returns result or option
+note: will cause the application to crash.
+  --> $DIR/panic_in_result.rs:33:9
+   |
+LL |         panic!("error");
+   |         ^^^^^^^^^^^^^^^^
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 6 previous errors
+