Auto merge of #10806 - y21:issue10741, r=giraffate

[`large_stack_arrays`]: check array initializer expressions

Fixes #10741.
Prior to this PR, the lint only checked array repeat expressions (ie. `[T; n]`). Now it also checks array initializer expressions.

changelog: [`large_stack_arrays`]: check array initializer expressions

clippy_lints/src/large_stack_arrays.rs

@@ -38,7 +38,7 @@ impl_lint_pass!(LargeStackArrays => [LARGE_STACK_ARRAYS]);
 
 impl<'tcx> LateLintPass<'tcx> for LargeStackArrays {
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
-        if let ExprKind::Repeat(_, _) = expr.kind
+        if let ExprKind::Repeat(_, _) | ExprKind::Array(_) = expr.kind
           && let ty::Array(element_type, cst) = cx.typeck_results().expr_ty(expr).kind()
           && let ConstKind::Value(ty::ValTree::Leaf(element_count)) = cst.kind()
           && let Ok(element_count) = element_count.try_to_target_usize(cx.tcx)

tests/ui/large_stack_arrays.rs

@@ -18,6 +18,19 @@ pub static DOESNOTLINT2: [u8; 512_001] = {
     [x; 512_001]
 };
 
+fn issue_10741() {
+    #[derive(Copy, Clone)]
+    struct Large([u32; 100_000]);
+
+    fn build() -> Large {
+        Large([0; 100_000])
+    }
+
+    let _x = [build(); 3];
+
+    let _y = [build(), build(), build()];
+}
+
 fn main() {
     let bad = (
         [0u32; 20_000_000],

tests/ui/large_stack_arrays.stderr

@@ -1,43 +1,59 @@
 error: allocating a local array larger than 512000 bytes
-  --> $DIR/large_stack_arrays.rs:23:9
+  --> $DIR/large_stack_arrays.rs:29:14
+   |
+LL |     let _x = [build(); 3];
+   |              ^^^^^^^^^^^^
+   |
+   = help: consider allocating on the heap with `vec![build(); 3].into_boxed_slice()`
+   = note: `-D clippy::large-stack-arrays` implied by `-D warnings`
+
+error: allocating a local array larger than 512000 bytes
+  --> $DIR/large_stack_arrays.rs:31:14
+   |
+LL |     let _y = [build(), build(), build()];
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider allocating on the heap with `vec![build(), build(), build()].into_boxed_slice()`
+
+error: allocating a local array larger than 512000 bytes
+  --> $DIR/large_stack_arrays.rs:36:9
    |
 LL |         [0u32; 20_000_000],
    |         ^^^^^^^^^^^^^^^^^^
    |
    = help: consider allocating on the heap with `vec![0u32; 20_000_000].into_boxed_slice()`
-   = note: `-D clippy::large-stack-arrays` implied by `-D warnings`
 
 error: allocating a local array larger than 512000 bytes
-  --> $DIR/large_stack_arrays.rs:24:9
+  --> $DIR/large_stack_arrays.rs:37:9
    |
 LL |         [S { data: [0; 32] }; 5000],
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider allocating on the heap with `vec![S { data: [0; 32] }; 5000].into_boxed_slice()`
 
 error: allocating a local array larger than 512000 bytes
-  --> $DIR/large_stack_arrays.rs:25:9
+  --> $DIR/large_stack_arrays.rs:38:9
    |
 LL |         [Some(""); 20_000_000],
    |         ^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider allocating on the heap with `vec![Some(""); 20_000_000].into_boxed_slice()`
 
 error: allocating a local array larger than 512000 bytes
-  --> $DIR/large_stack_arrays.rs:26:9
+  --> $DIR/large_stack_arrays.rs:39:9
    |
 LL |         [E::T(0); 5000],
    |         ^^^^^^^^^^^^^^^
    |
    = help: consider allocating on the heap with `vec![E::T(0); 5000].into_boxed_slice()`
 
 error: allocating a local array larger than 512000 bytes
-  --> $DIR/large_stack_arrays.rs:27:9
+  --> $DIR/large_stack_arrays.rs:40:9
    |
 LL |         [0u8; usize::MAX],
    |         ^^^^^^^^^^^^^^^^^
    |
    = help: consider allocating on the heap with `vec![0u8; usize::MAX].into_boxed_slice()`
 
-error: aborting due to 5 previous errors
+error: aborting due to 7 previous errors