{expect,unwrap}_used: add options to lint at compilation time

By default, do not lint `.unwrap()` and `.expect(…)` in always const
contexts, as a failure would be detected at compile time anyway.

New options `allow_expect_in_consts` and `allow_unwrap_in_consts`,
defaulting to `true`, can be turned unset to still lint in always const
contexts.

Author: samueltardieu

CHANGELOG.md

@@ -6268,6 +6268,7 @@ Released 2018-09-13
 [`accept-comment-above-statement`]: https://doc.rust-lang.org/clippy/lint_configuration.html#accept-comment-above-statement
 [`allow-comparison-to-zero`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-comparison-to-zero
 [`allow-dbg-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-dbg-in-tests
+[`allow-expect-in-consts`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-expect-in-consts
 [`allow-expect-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-expect-in-tests
 [`allow-indexing-slicing-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-indexing-slicing-in-tests
 [`allow-mixed-uninlined-format-args`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-mixed-uninlined-format-args
@@ -6276,6 +6277,7 @@ Released 2018-09-13
 [`allow-print-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-print-in-tests
 [`allow-private-module-inception`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-private-module-inception
 [`allow-renamed-params-for`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-renamed-params-for
+[`allow-unwrap-in-consts`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-unwrap-in-consts
 [`allow-unwrap-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-unwrap-in-tests
 [`allow-useless-vec-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-useless-vec-in-tests
 [`allowed-dotfiles`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allowed-dotfiles

book/src/lint_configuration.md

@@ -71,6 +71,16 @@ Whether `dbg!` should be allowed in test functions or `#[cfg(test)]`
 * [`dbg_macro`](https://rust-lang.github.io/rust-clippy/master/index.html#dbg_macro)
 
 
+## `allow-expect-in-consts`
+Whether `expect` should be allowed in code always evaluated at compile time
+
+**Default Value:** `true`
+
+---
+**Affected lints:**
+* [`expect_used`](https://rust-lang.github.io/rust-clippy/master/index.html#expect_used)
+
+
 ## `allow-expect-in-tests`
 Whether `expect` should be allowed in test functions or `#[cfg(test)]`
 
@@ -164,6 +174,16 @@ default configuration of Clippy. By default, any configuration will replace the
 * [`renamed_function_params`](https://rust-lang.github.io/rust-clippy/master/index.html#renamed_function_params)
 
 
+## `allow-unwrap-in-consts`
+Whether `unwrap` should be allowed in code always evaluated at compile time
+
+**Default Value:** `true`
+
+---
+**Affected lints:**
+* [`unwrap_used`](https://rust-lang.github.io/rust-clippy/master/index.html#unwrap_used)
+
+
 ## `allow-unwrap-in-tests`
 Whether `unwrap` should be allowed in test functions or `#[cfg(test)]`
 

clippy_config/src/conf.rs

@@ -288,6 +288,9 @@ define_Conf! {
     /// Whether `dbg!` should be allowed in test functions or `#[cfg(test)]`
     #[lints(dbg_macro)]
     allow_dbg_in_tests: bool = false,
+    /// Whether `expect` should be allowed in code always evaluated at compile time
+    #[lints(expect_used)]
+    allow_expect_in_consts: bool = true,
     /// Whether `expect` should be allowed in test functions or `#[cfg(test)]`
     #[lints(expect_used)]
     allow_expect_in_tests: bool = false,
@@ -325,6 +328,9 @@ define_Conf! {
     #[lints(renamed_function_params)]
     allow_renamed_params_for: Vec<String> =
         DEFAULT_ALLOWED_TRAITS_WITH_RENAMED_PARAMS.iter().map(ToString::to_string).collect(),
+    /// Whether `unwrap` should be allowed in code always evaluated at compile time
+    #[lints(unwrap_used)]
+    allow_unwrap_in_consts: bool = true,
     /// Whether `unwrap` should be allowed in test functions or `#[cfg(test)]`
     #[lints(unwrap_used)]
     allow_unwrap_in_tests: bool = false,

clippy_lints/src/methods/mod.rs

@@ -4406,11 +4406,14 @@ declare_clippy_lint! {
     "using `Option::and_then` or `Result::and_then` to chain a computation that returns an `Option` or a `Result`"
 }
 
+#[expect(clippy::struct_excessive_bools)]
 pub struct Methods {
     avoid_breaking_exported_api: bool,
     msrv: Msrv,
     allow_expect_in_tests: bool,
     allow_unwrap_in_tests: bool,
+    allow_expect_in_consts: bool,
+    allow_unwrap_in_consts: bool,
     allowed_dotfiles: FxHashSet<&'static str>,
     format_args: FormatArgsStorage,
 }
@@ -4425,6 +4428,8 @@ impl Methods {
             msrv: conf.msrv.clone(),
             allow_expect_in_tests: conf.allow_expect_in_tests,
             allow_unwrap_in_tests: conf.allow_unwrap_in_tests,
+            allow_expect_in_consts: conf.allow_expect_in_consts,
+            allow_unwrap_in_consts: conf.allow_unwrap_in_consts,
             allowed_dotfiles,
             format_args,
         }
@@ -4918,6 +4923,7 @@ impl Methods {
                             expr,
                             recv,
                             false,
+                            self.allow_expect_in_consts,
                             self.allow_expect_in_tests,
                             unwrap_expect_used::Variant::Expect,
                         ),
@@ -4931,6 +4937,7 @@ impl Methods {
                         expr,
                         recv,
                         true,
+                        self.allow_expect_in_consts,
                         self.allow_expect_in_tests,
                         unwrap_expect_used::Variant::Expect,
                     );
@@ -5304,6 +5311,7 @@ impl Methods {
                         expr,
                         recv,
                         false,
+                        self.allow_unwrap_in_consts,
                         self.allow_unwrap_in_tests,
                         unwrap_expect_used::Variant::Unwrap,
                     );
@@ -5315,6 +5323,7 @@ impl Methods {
                         expr,
                         recv,
                         true,
+                        self.allow_unwrap_in_consts,
                         self.allow_unwrap_in_tests,
                         unwrap_expect_used::Variant::Unwrap,
                     );

clippy_lints/src/methods/unwrap_expect_used.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::ty::{is_never_like, is_type_diagnostic_item};
-use clippy_utils::{is_in_test, is_lint_allowed};
+use clippy_utils::{is_in_test, is_inside_always_const_context, is_lint_allowed};
 use rustc_hir::Expr;
 use rustc_lint::{LateContext, Lint};
 use rustc_middle::ty;
@@ -39,6 +39,7 @@ pub(super) fn check(
     expr: &Expr<'_>,
     recv: &Expr<'_>,
     is_err: bool,
+    allow_unwrap_in_consts: bool,
     allow_unwrap_in_tests: bool,
     variant: Variant,
 ) {
@@ -65,6 +66,10 @@ pub(super) fn check(
         return;
     }
 
+    if allow_unwrap_in_consts && is_inside_always_const_context(cx.tcx, expr.hir_id) {
+        return;
+    }
+
     span_lint_and_then(
         cx,
         variant.lint(),

tests/ui-toml/expect_used/clippy.toml

@@ -1 +1,2 @@
+allow-expect-in-consts = false
 allow-expect-in-tests = true

tests/ui-toml/expect_used/expect_used.rs

@@ -1,4 +1,5 @@
 //@compile-flags: --test
+//@no-rustfix
 #![warn(clippy::expect_used)]
 #![allow(clippy::unnecessary_literal_unwrap)]
 
@@ -15,6 +16,14 @@ fn expect_result() {
 fn main() {
     expect_option();
     expect_result();
+
+    const SOME: Option<i32> = Some(3);
+    const UNWRAPPED: i32 = SOME.expect("Not three?");
+    //~^ ERROR: used `expect()` on an `Option` value
+    const {
+        SOME.expect("Still not three?");
+        //~^ ERROR: used `expect()` on an `Option` value
+    }
 }
 
 #[test]

tests/ui-toml/expect_used/expect_used.stderr

@@ -1,5 +1,5 @@
 error: used `expect()` on an `Option` value
-  --> tests/ui-toml/expect_used/expect_used.rs:7:13
+  --> tests/ui-toml/expect_used/expect_used.rs:8:13
    |
 LL |     let _ = opt.expect("");
    |             ^^^^^^^^^^^^^^
@@ -9,12 +9,28 @@ LL |     let _ = opt.expect("");
    = help: to override `-D warnings` add `#[allow(clippy::expect_used)]`
 
 error: used `expect()` on a `Result` value
-  --> tests/ui-toml/expect_used/expect_used.rs:12:13
+  --> tests/ui-toml/expect_used/expect_used.rs:13:13
    |
 LL |     let _ = res.expect("");
    |             ^^^^^^^^^^^^^^
    |
    = note: if this value is an `Err`, it will panic
 
-error: aborting due to 2 previous errors
+error: used `expect()` on an `Option` value
+  --> tests/ui-toml/expect_used/expect_used.rs:21:28
+   |
+LL |     const UNWRAPPED: i32 = SOME.expect("Not three?");
+   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: if this value is `None`, it will panic
+
+error: used `expect()` on an `Option` value
+  --> tests/ui-toml/expect_used/expect_used.rs:24:9
+   |
+LL |         SOME.expect("Still not three?");
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: if this value is `None`, it will panic
+
+error: aborting due to 4 previous errors
 

tests/ui-toml/toml_unknown_key/conf_unknown_key.stderr

@@ -5,6 +5,7 @@ error: error reading Clippy's configuration file: unknown field `foobar`, expect
            accept-comment-above-statement
            allow-comparison-to-zero
            allow-dbg-in-tests
+           allow-expect-in-consts
            allow-expect-in-tests
            allow-indexing-slicing-in-tests
            allow-mixed-uninlined-format-args
@@ -13,6 +14,7 @@ error: error reading Clippy's configuration file: unknown field `foobar`, expect
            allow-print-in-tests
            allow-private-module-inception
            allow-renamed-params-for
+           allow-unwrap-in-consts
            allow-unwrap-in-tests
            allow-useless-vec-in-tests
            allowed-dotfiles
@@ -94,6 +96,7 @@ error: error reading Clippy's configuration file: unknown field `barfoo`, expect
            accept-comment-above-statement
            allow-comparison-to-zero
            allow-dbg-in-tests
+           allow-expect-in-consts
            allow-expect-in-tests
            allow-indexing-slicing-in-tests
            allow-mixed-uninlined-format-args
@@ -102,6 +105,7 @@ error: error reading Clippy's configuration file: unknown field `barfoo`, expect
            allow-print-in-tests
            allow-private-module-inception
            allow-renamed-params-for
+           allow-unwrap-in-consts
            allow-unwrap-in-tests
            allow-useless-vec-in-tests
            allowed-dotfiles
@@ -183,6 +187,7 @@ error: error reading Clippy's configuration file: unknown field `allow_mixed_uni
            accept-comment-above-statement
            allow-comparison-to-zero
            allow-dbg-in-tests
+           allow-expect-in-consts
            allow-expect-in-tests
            allow-indexing-slicing-in-tests
            allow-mixed-uninlined-format-args
@@ -191,6 +196,7 @@ error: error reading Clippy's configuration file: unknown field `allow_mixed_uni
            allow-print-in-tests
            allow-private-module-inception
            allow-renamed-params-for
+           allow-unwrap-in-consts
            allow-unwrap-in-tests
            allow-useless-vec-in-tests
            allowed-dotfiles

tests/ui-toml/unwrap_used/clippy.toml

@@ -1 +1,2 @@
+allow-unwrap-in-consts = false
 allow-unwrap-in-tests = true

tests/ui-toml/unwrap_used/unwrap_used_const.rs

@@ -0,0 +1,11 @@
+#![warn(clippy::unwrap_used)]
+
+fn main() {
+    const SOME: Option<i32> = Some(3);
+    const UNWRAPPED: i32 = SOME.unwrap();
+    //~^ ERROR: used `unwrap()` on an `Option` value
+    const {
+        SOME.unwrap();
+        //~^ ERROR: used `unwrap()` on an `Option` value
+    }
+}

tests/ui-toml/unwrap_used/unwrap_used_const.stderr

@@ -0,0 +1,22 @@
+error: used `unwrap()` on an `Option` value
+  --> tests/ui-toml/unwrap_used/unwrap_used_const.rs:5:28
+   |
+LL |     const UNWRAPPED: i32 = SOME.unwrap();
+   |                            ^^^^^^^^^^^^^
+   |
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
+   = note: `-D clippy::unwrap-used` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::unwrap_used)]`
+
+error: used `unwrap()` on an `Option` value
+  --> tests/ui-toml/unwrap_used/unwrap_used_const.rs:8:9
+   |
+LL |         SOME.unwrap();
+   |         ^^^^^^^^^^^^^
+   |
+   = note: if this value is `None`, it will panic
+   = help: consider using `expect()` to provide a better panic message
+
+error: aborting due to 2 previous errors
+

tests/ui/unwrap_expect_used.rs

@@ -50,4 +50,15 @@ fn main() {
     //~^ ERROR: used `unwrap_err()` on a `Result` value
     a.expect_err("Hello error!");
     //~^ ERROR: used `expect_err()` on a `Result` value
+
+    // Don't trigger in compile time contexts by default
+    const SOME: Option<i32> = Some(3);
+    const UNWRAPPED: i32 = SOME.unwrap();
+    const EXPECTED: i32 = SOME.expect("Not three?");
+    const {
+        SOME.unwrap();
+    }
+    const {
+        SOME.expect("Still not three?");
+    }
 }