Ignore non ExprKind::{Path,Lit) inside const context

- remove now dead code in ASSERTIONS_ON_CONSTANTS
  cc rust-lang#11966
- Partially revert "ignore `assertions-on-constants` in const contexts"
  This reverts commit c7074de420a2192fb40d3f2194a20dd0d1b65cc6.

Author: tesuji

clippy_lints/src/assertions_on_constants.rs

@@ -1,8 +1,8 @@
-use clippy_utils::consts::{constant_with_source, Constant, ConstantSource};
+use clippy_utils::consts::{constant, Constant};
 use clippy_utils::diagnostics::span_lint_and_help;
 use clippy_utils::is_inside_always_const_context;
 use clippy_utils::macros::{find_assert_args, root_macro_call_first_node, PanicExpn};
-use rustc_hir::{Expr, Item, ItemKind, Node};
+use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::declare_lint_pass;
 use rustc_span::sym;
@@ -32,10 +32,6 @@ declare_lint_pass!(AssertionsOnConstants => [ASSERTIONS_ON_CONSTANTS]);
 
 impl<'tcx> LateLintPass<'tcx> for AssertionsOnConstants {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
-        if is_inside_always_const_context(cx.tcx, e.hir_id) {
-            return;
-        }
-
         let Some(macro_call) = root_macro_call_first_node(cx, e) else {
             return;
         };
@@ -47,17 +43,16 @@ impl<'tcx> LateLintPass<'tcx> for AssertionsOnConstants {
         let Some((condition, panic_expn)) = find_assert_args(cx, e, macro_call.expn) else {
             return;
         };
-        let Some((Constant::Bool(val), source)) = constant_with_source(cx, cx.typeck_results(), condition) else {
+        let Some(Constant::Bool(val)) = constant(cx, cx.typeck_results(), condition) else {
             return;
         };
-        if let ConstantSource::Constant = source
-            && let Node::Item(Item {
-                kind: ItemKind::Const(..),
-                ..
-            }) = cx.tcx.parent_hir_node(e.hir_id)
-        {
-            return;
+
+        match condition.kind {
+            ExprKind::Path(..) | ExprKind::Lit(_) => {},
+            _ if is_inside_always_const_context(cx.tcx, e.hir_id) => return,
+            _ => {},
         }
+
         if val {
             span_lint_and_help(
                 cx,

tests/ui/assertions_on_constants.rs

@@ -1,4 +1,4 @@
-#![allow(non_fmt_panics, clippy::needless_bool)]
+#![allow(non_fmt_panics, clippy::needless_bool, clippy::eq_op)]
 
 macro_rules! assert_const {
     ($len:expr) => {
@@ -47,14 +47,18 @@ fn main() {
     assert!(!CFG_FLAG);
 
     const _: () = assert!(true);
+    //~^ ERROR: `assert!(true)` will be optimized out by the compiler
+
+    assert!(8 == (7 + 1));
+    //~^ ERROR: `assert!(true)` will be optimized out by the compiler
 
     // Don't lint if the value is dependent on a defined constant:
     const N: usize = 1024;
     const _: () = assert!(N.is_power_of_two());
 }
 
-#[allow(clippy::eq_op)]
 const _: () = {
     assert!(true);
+    //~^ ERROR: `assert!(true)` will be optimized out by the compiler
     assert!(8 == (7 + 1));
 };

tests/ui/assertions_on_constants.stderr

@@ -72,5 +72,29 @@ LL |     debug_assert!(true);
    |
    = help: remove it
 
-error: aborting due to 9 previous errors
+error: `assert!(true)` will be optimized out by the compiler
+  --> tests/ui/assertions_on_constants.rs:49:19
+   |
+LL |     const _: () = assert!(true);
+   |                   ^^^^^^^^^^^^^
+   |
+   = help: remove it
+
+error: `assert!(true)` will be optimized out by the compiler
+  --> tests/ui/assertions_on_constants.rs:52:5
+   |
+LL |     assert!(8 == (7 + 1));
+   |     ^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: remove it
+
+error: `assert!(true)` will be optimized out by the compiler
+  --> tests/ui/assertions_on_constants.rs:61:5
+   |
+LL |     assert!(true);
+   |     ^^^^^^^^^^^^^
+   |
+   = help: remove it
+
+error: aborting due to 12 previous errors
 

tests/ui/unnecessary_operation.fixed

@@ -124,4 +124,5 @@ const _: () = {
 
 const fn foo() {
     assert!([42, 55].len() > get_usize());
+    //~^ ERROR: unnecessary operation
 }

tests/ui/unnecessary_operation.rs

@@ -128,4 +128,5 @@ const _: () = {
 
 const fn foo() {
     [42, 55][get_usize()];
+    //~^ ERROR: unnecessary operation
 }