Auto merge of #13620 - GnomedDev:large-const-array-compute-const, r=Manishearth

Fire large_const_arrays for computed array lengths

changelog: [`large_const_arrays`]: Lint now fires when the length is determined by an expression

Author: bors

clippy_lints/src/large_const_arrays.rs

@@ -4,7 +4,7 @@ use rustc_errors::Applicability;
 use rustc_hir::{Item, ItemKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::layout::LayoutOf;
-use rustc_middle::ty::{self, ConstKind};
+use rustc_middle::ty::{self, ParamEnv};
 use rustc_session::impl_lint_pass;
 use rustc_span::{BytePos, Pos, Span};
 
@@ -56,7 +56,7 @@ impl<'tcx> LateLintPass<'tcx> for LargeConstArrays {
             && !item.span.from_expansion()
             && let ty = cx.tcx.type_of(item.owner_id).instantiate_identity()
             && let ty::Array(element_type, cst) = ty.kind()
-            && let ConstKind::Value(_, ty::ValTree::Leaf(element_count)) = cst.kind()
+            && let Ok((_, ty::ValTree::Leaf(element_count))) = cst.eval(cx.tcx, ParamEnv::empty(), item.span)
             && let element_count = element_count.to_target_usize(cx.tcx)
             && let Ok(element_size) = cx.layout_of(*element_type).map(|l| l.size.bytes())
             && u128::from(self.maximum_allowed_size) < u128::from(element_count) * u128::from(element_size)

tests/ui/large_const_arrays.fixed

@@ -9,11 +9,13 @@ pub struct S {
 // Should lint
 pub(crate) static FOO_PUB_CRATE: [u32; 1_000_000] = [0u32; 1_000_000];
 pub static FOO_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
+static FOO_COMPUTED: [u32; 1_000 * 100] = [0u32; 1_000 * 100];
 static FOO: [u32; 1_000_000] = [0u32; 1_000_000];
 
 // Good
 pub(crate) const G_FOO_PUB_CRATE: [u32; 250] = [0u32; 250];
 pub const G_FOO_PUB: [u32; 250] = [0u32; 250];
+const G_FOO_COMPUTED: [u32; 25 * 10] = [0u32; 25 * 10];
 const G_FOO: [u32; 250] = [0u32; 250];
 
 fn main() {

tests/ui/large_const_arrays.rs

@@ -9,11 +9,13 @@ pub struct S {
 // Should lint
 pub(crate) const FOO_PUB_CRATE: [u32; 1_000_000] = [0u32; 1_000_000];
 pub const FOO_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
+const FOO_COMPUTED: [u32; 1_000 * 100] = [0u32; 1_000 * 100];
 const FOO: [u32; 1_000_000] = [0u32; 1_000_000];
 
 // Good
 pub(crate) const G_FOO_PUB_CRATE: [u32; 250] = [0u32; 250];
 pub const G_FOO_PUB: [u32; 250] = [0u32; 250];
+const G_FOO_COMPUTED: [u32; 25 * 10] = [0u32; 25 * 10];
 const G_FOO: [u32; 250] = [0u32; 250];
 
 fn main() {

tests/ui/large_const_arrays.stderr

@@ -20,58 +20,66 @@ LL | pub const FOO_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
 error: large array defined as const
   --> tests/ui/large_const_arrays.rs:12:1
    |
+LL | const FOO_COMPUTED: [u32; 1_000 * 100] = [0u32; 1_000 * 100];
+   | -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   | |
+   | help: make this a static item: `static`
+
+error: large array defined as const
+  --> tests/ui/large_const_arrays.rs:13:1
+   |
 LL | const FOO: [u32; 1_000_000] = [0u32; 1_000_000];
    | -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    | |
    | help: make this a static item: `static`
 
 error: large array defined as const
-  --> tests/ui/large_const_arrays.rs:21:5
+  --> tests/ui/large_const_arrays.rs:23:5
    |
 LL |     pub const BAR_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
    |     ^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         |
    |         help: make this a static item: `static`
 
 error: large array defined as const
-  --> tests/ui/large_const_arrays.rs:22:5
+  --> tests/ui/large_const_arrays.rs:24:5
    |
 LL |     const BAR: [u32; 1_000_000] = [0u32; 1_000_000];
    |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |     |
    |     help: make this a static item: `static`
 
 error: large array defined as const
-  --> tests/ui/large_const_arrays.rs:23:5
+  --> tests/ui/large_const_arrays.rs:25:5
    |
 LL |     pub const BAR_STRUCT_PUB: [S; 5_000] = [S { data: [0; 32] }; 5_000];
    |     ^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         |
    |         help: make this a static item: `static`
 
 error: large array defined as const
-  --> tests/ui/large_const_arrays.rs:24:5
+  --> tests/ui/large_const_arrays.rs:26:5
    |
 LL |     const BAR_STRUCT: [S; 5_000] = [S { data: [0; 32] }; 5_000];
    |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |     |
    |     help: make this a static item: `static`
 
 error: large array defined as const
-  --> tests/ui/large_const_arrays.rs:25:5
+  --> tests/ui/large_const_arrays.rs:27:5
    |
 LL |     pub const BAR_S_PUB: [Option<&str>; 200_000] = [Some("str"); 200_000];
    |     ^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         |
    |         help: make this a static item: `static`
 
 error: large array defined as const
-  --> tests/ui/large_const_arrays.rs:26:5
+  --> tests/ui/large_const_arrays.rs:28:5
    |
 LL |     const BAR_S: [Option<&str>; 200_000] = [Some("str"); 200_000];
    |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |     |
    |     help: make this a static item: `static`
 
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors