Auto merge of #3582 - Arkweid:add-lints-aseert-checks, r=flip1995

Add assert(true) and assert(false) lints

This PR add two lints on assert!(true) and assert!(false).
#3575

12 files changed, 154 insertions, 6 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7acf9bc1eaa..14c1b0e4d3f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -616,6 +616,7 @@ All notable changes to this project will be documented in this file.
 [`absurd_extreme_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#absurd_extreme_comparisons
 [`almost_swapped`]: https://rust-lang.github.io/rust-clippy/master/index.html#almost_swapped
 [`approx_constant`]: https://rust-lang.github.io/rust-clippy/master/index.html#approx_constant
+[`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
 [`bad_bit_mask`]: https://rust-lang.github.io/rust-clippy/master/index.html#bad_bit_mask
diff --git a/README.md b/README.md
index 24a57450b85..6473b8efc54 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@
 
 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
 
-[There are 291 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+[There are 292 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
 
 We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
 
diff --git a/clippy_lints/src/assertions_on_constants.rs b/clippy_lints/src/assertions_on_constants.rs
new file mode 100644
index 00000000000..a148cb1c3a6
--- /dev/null
+++ b/clippy_lints/src/assertions_on_constants.rs
@@ -0,0 +1,78 @@
+use crate::consts::{constant, Constant};
+use crate::rustc::hir::{Expr, ExprKind};
+use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use crate::rustc::{declare_tool_lint, lint_array};
+use crate::syntax::ast::LitKind;
+use crate::utils::{is_direct_expn_of, span_help_and_lint};
+use if_chain::if_chain;
+
+/// **What it does:** Check to call assert!(true/false)
+///
+/// **Why is this bad?** Will be optimized out by the compiler or should probably be replaced by a
+/// panic!() or unreachable!()
+///
+/// **Known problems:** None
+///
+/// **Example:**
+/// ```rust
+/// assert!(false)
+/// // or
+/// assert!(true)
+/// // or
+/// const B: bool = false;
+/// assert!(B)
+/// ```
+declare_clippy_lint! {
+    pub ASSERTIONS_ON_CONSTANTS,
+    style,
+    "assert!(true/false) will be optimized out by the compiler/should probably be replaced by a panic!() or unreachable!()"
+}
+
+pub struct AssertionsOnConstants;
+
+impl LintPass for AssertionsOnConstants {
+    fn get_lints(&self) -> LintArray {
+        lint_array![ASSERTIONS_ON_CONSTANTS]
+    }
+}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssertionsOnConstants {
+    fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
+        if_chain! {
+            if is_direct_expn_of(e.span, "assert").is_some();
+            if let ExprKind::Unary(_, ref lit) = e.node;
+            then {
+                if let ExprKind::Lit(ref inner) = lit.node {
+                    match inner.node {
+                        LitKind::Bool(true) => {
+                            span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
+                                "assert!(true) will be optimized out by the compiler",
+                                "remove it");
+                        },
+                        LitKind::Bool(false) => {
+                            span_help_and_lint(
+                                cx, ASSERTIONS_ON_CONSTANTS, e.span,
+                                "assert!(false) should probably be replaced",
+                                "use panic!() or unreachable!()");
+                        },
+                        _ => (),
+                    }
+                } else if let Some(bool_const) = constant(cx, cx.tables, lit) {
+                    match bool_const.0 {
+                        Constant::Bool(true) => {
+                            span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
+                                "assert!(const: true) will be optimized out by the compiler",
+                                "remove it");
+                        },
+                        Constant::Bool(false) => {
+                            span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
+                                "assert!(const: false) should probably be replaced",
+                                "use panic!() or unreachable!()");
+                        },
+                        _ => (),
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 608094c833d..9d77c3c64a2 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -78,6 +78,7 @@ mod utils;
 // begin lints modules, do not remove this comment, it’s used in `update_lints`
 pub mod approx_const;
 pub mod arithmetic;
+pub mod assertions_on_constants;
 pub mod assign_ops;
 pub mod attrs;
 pub mod bit_mask;
@@ -477,6 +478,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
     reg.register_late_lint_pass(box redundant_clone::RedundantClone);
     reg.register_late_lint_pass(box slow_vector_initialization::Pass);
     reg.register_late_lint_pass(box types::RefToMut);
+    reg.register_late_lint_pass(box assertions_on_constants::AssertionsOnConstants);
 
     reg.register_lint_group("clippy::restriction", Some("clippy_restriction"), vec![
         arithmetic::FLOAT_ARITHMETIC,
@@ -554,6 +556,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
 
     reg.register_lint_group("clippy::all", Some("clippy"), vec![
         approx_const::APPROX_CONSTANT,
+        assertions_on_constants::ASSERTIONS_ON_CONSTANTS,
         assign_ops::ASSIGN_OP_PATTERN,
         assign_ops::MISREFACTORED_ASSIGN_OP,
         attrs::DEPRECATED_CFG_ATTR,
@@ -776,6 +779,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
     ]);
 
     reg.register_lint_group("clippy::style", Some("clippy_style"), vec![
+        assertions_on_constants::ASSERTIONS_ON_CONSTANTS,
         assign_ops::ASSIGN_OP_PATTERN,
         attrs::UNKNOWN_CLIPPY_LINTS,
         bit_mask::VERBOSE_BIT_MASK,
diff --git a/tests/missing-test-files.rs b/tests/missing-test-files.rs
index 558e001d3d1..bd0cee75644 100644
--- a/tests/missing-test-files.rs
+++ b/tests/missing-test-files.rs
@@ -1,3 +1,5 @@
+#![allow(clippy::assertions_on_constants)]
+
 use std::fs::{self, DirEntry};
 use std::path::Path;
 
diff --git a/tests/ui/assertions_on_constants.rs b/tests/ui/assertions_on_constants.rs
new file mode 100644
index 00000000000..daeceebd3a2
--- /dev/null
+++ b/tests/ui/assertions_on_constants.rs
@@ -0,0 +1,12 @@
+fn main() {
+    assert!(true);
+    assert!(false);
+    assert!(true, "true message");
+    assert!(false, "false message");
+
+    const B: bool = true;
+    assert!(B);
+
+    const C: bool = false;
+    assert!(C);
+}
diff --git a/tests/ui/assertions_on_constants.stderr b/tests/ui/assertions_on_constants.stderr
new file mode 100644
index 00000000000..e8001acceb1
--- /dev/null
+++ b/tests/ui/assertions_on_constants.stderr
@@ -0,0 +1,51 @@
+error: assert!(true) will be optimized out by the compiler
+  --> $DIR/assertions_on_constants.rs:2:5
+   |
+LL |     assert!(true);
+   |     ^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::assertions-on-constants` implied by `-D warnings`
+   = help: remove it
+
+error: assert!(false) should probably be replaced
+  --> $DIR/assertions_on_constants.rs:3:5
+   |
+LL |     assert!(false);
+   |     ^^^^^^^^^^^^^^^
+   |
+   = help: use panic!() or unreachable!()
+
+error: assert!(true) will be optimized out by the compiler
+  --> $DIR/assertions_on_constants.rs:4:5
+   |
+LL |     assert!(true, "true message");
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: remove it
+
+error: assert!(false) should probably be replaced
+  --> $DIR/assertions_on_constants.rs:5:5
+   |
+LL |     assert!(false, "false message");
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: use panic!() or unreachable!()
+
+error: assert!(const: true) will be optimized out by the compiler
+  --> $DIR/assertions_on_constants.rs:8:5
+   |
+LL |     assert!(B);
+   |     ^^^^^^^^^^^
+   |
+   = help: remove it
+
+error: assert!(const: false) should probably be replaced
+  --> $DIR/assertions_on_constants.rs:11:5
+   |
+LL |     assert!(C);
+   |     ^^^^^^^^^^^
+   |
+   = help: use panic!() or unreachable!()
+
+error: aborting due to 6 previous errors
+
diff --git a/tests/ui/attrs.rs b/tests/ui/attrs.rs
index 4dbb5c67f5d..91b65a43be7 100644
--- a/tests/ui/attrs.rs
+++ b/tests/ui/attrs.rs
@@ -1,5 +1,5 @@
 #![warn(clippy::inline_always, clippy::deprecated_semver)]
-
+#![allow(clippy::assertions_on_constants)]
 #[inline(always)]
 fn test_attr_lint() {
     assert!(true)
diff --git a/tests/ui/collapsible_if.fixed b/tests/ui/collapsible_if.fixed
index 2c6dd95a637..3c7de56406e 100644
--- a/tests/ui/collapsible_if.fixed
+++ b/tests/ui/collapsible_if.fixed
@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(clippy::cyclomatic_complexity)]
+#![allow(clippy::cyclomatic_complexity, clippy::assertions_on_constants)]
 
 #[rustfmt::skip]
 #[warn(clippy::collapsible_if)]
diff --git a/tests/ui/collapsible_if.rs b/tests/ui/collapsible_if.rs
index f482d7704de..e46d7537577 100644
--- a/tests/ui/collapsible_if.rs
+++ b/tests/ui/collapsible_if.rs
@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(clippy::cyclomatic_complexity)]
+#![allow(clippy::cyclomatic_complexity, clippy::assertions_on_constants)]
 
 #[rustfmt::skip]
 #[warn(clippy::collapsible_if)]
diff --git a/tests/ui/empty_line_after_outer_attribute.rs b/tests/ui/empty_line_after_outer_attribute.rs
index 1e067a54232..b43dc200825 100644
--- a/tests/ui/empty_line_after_outer_attribute.rs
+++ b/tests/ui/empty_line_after_outer_attribute.rs
@@ -1,5 +1,5 @@
 #![warn(clippy::empty_line_after_outer_attr)]
-
+#![allow(clippy::assertions_on_constants)]
 // This should produce a warning
 #[crate_type = "lib"]
 
diff --git a/tests/ui/panic_unimplemented.rs b/tests/ui/panic_unimplemented.rs
index f205e07cd30..92290da8a6a 100644
--- a/tests/ui/panic_unimplemented.rs
+++ b/tests/ui/panic_unimplemented.rs
@@ -1,5 +1,5 @@
 #![warn(clippy::panic_params, clippy::unimplemented)]
-
+#![allow(clippy::assertions_on_constants)]
 fn missing() {
     if true {
         panic!("{}");