Auto merge of #6485 - phansch:macro-check-large-enum-variant, r=llogiq

Don't trigger large_enum_variant in external macros

Closes #1776 (the potential JSON output issue is not something we can fix in Clippy and I can't reproduce it anymore)

changelog: Don't trigger [`large_enum_variant`] in external macros

clippy_lints/src/large_enum_variant.rs

@@ -4,6 +4,7 @@
 use rustc_errors::Applicability;
 use rustc_hir::{Item, ItemKind, VariantData};
 use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::lint::in_external_macro;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_target::abi::LayoutOf;
 
@@ -58,6 +59,9 @@ pub fn new(maximum_size_difference_allowed: u64) -> Self {
 
 impl<'tcx> LateLintPass<'tcx> for LargeEnumVariant {
     fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
+        if in_external_macro(cx.tcx.sess, item.span) {
+            return;
+        }
         let did = cx.tcx.hir().local_def_id(item.hir_id);
         if let ItemKind::Enum(ref def, _) = item.kind {
             let ty = cx.tcx.type_of(did);

tests/ui/auxiliary/macro_rules.rs

@@ -84,3 +84,13 @@ macro_rules! as_conv {
         0u32 as u64
     };
 }
+
+#[macro_export]
+macro_rules! large_enum_variant {
+    () => {
+        enum LargeEnumInMacro {
+            A(i32),
+            B([i32; 8000]),
+        }
+    };
+}

tests/ui/large_enum_variant.rs

@@ -1,7 +1,12 @@
+// aux-build:macro_rules.rs
+
 #![allow(dead_code)]
 #![allow(unused_variables)]
 #![warn(clippy::large_enum_variant)]
 
+#[macro_use]
+extern crate macro_rules;
+
 enum LargeEnum {
     A(i32),
     B([i32; 8000]),
@@ -51,4 +56,6 @@ enum LargeEnumOk {
     LargeB([i32; 8001]),
 }
 
-fn main() {}
+fn main() {
+    large_enum_variant!();
+}

tests/ui/large_enum_variant.stderr

@@ -1,12 +1,12 @@
 error: large size difference between variants
-  --> $DIR/large_enum_variant.rs:7:5
+  --> $DIR/large_enum_variant.rs:12:5
    |
 LL |     B([i32; 8000]),
    |     ^^^^^^^^^^^^^^ this variant is 32000 bytes
    |
    = note: `-D clippy::large-enum-variant` implied by `-D warnings`
 note: and the second-largest variant is 4 bytes:
-  --> $DIR/large_enum_variant.rs:6:5
+  --> $DIR/large_enum_variant.rs:11:5
    |
 LL |     A(i32),
    |     ^^^^^^
@@ -16,13 +16,13 @@ LL |     B(Box<[i32; 8000]>),
    |       ^^^^^^^^^^^^^^^^
 
 error: large size difference between variants
-  --> $DIR/large_enum_variant.rs:31:5
+  --> $DIR/large_enum_variant.rs:36:5
    |
 LL |     ContainingLargeEnum(LargeEnum),
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this variant is 32004 bytes
    |
 note: and the second-largest variant is 8 bytes:
-  --> $DIR/large_enum_variant.rs:30:5
+  --> $DIR/large_enum_variant.rs:35:5
    |
 LL |     VariantOk(i32, u32),
    |     ^^^^^^^^^^^^^^^^^^^
@@ -32,30 +32,30 @@ LL |     ContainingLargeEnum(Box<LargeEnum>),
    |                         ^^^^^^^^^^^^^^
 
 error: large size difference between variants
-  --> $DIR/large_enum_variant.rs:41:5
+  --> $DIR/large_enum_variant.rs:46:5
    |
 LL |     StructLikeLarge { x: [i32; 8000], y: i32 },
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this variant is 32004 bytes
    |
 note: and the second-largest variant is 8 bytes:
-  --> $DIR/large_enum_variant.rs:40:5
+  --> $DIR/large_enum_variant.rs:45:5
    |
 LL |     VariantOk(i32, u32),
    |     ^^^^^^^^^^^^^^^^^^^
 help: consider boxing the large fields to reduce the total size of the enum
-  --> $DIR/large_enum_variant.rs:41:5
+  --> $DIR/large_enum_variant.rs:46:5
    |
 LL |     StructLikeLarge { x: [i32; 8000], y: i32 },
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: large size difference between variants
-  --> $DIR/large_enum_variant.rs:46:5
+  --> $DIR/large_enum_variant.rs:51:5
    |
 LL |     StructLikeLarge2 { x: [i32; 8000] },
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this variant is 32000 bytes
    |
 note: and the second-largest variant is 8 bytes:
-  --> $DIR/large_enum_variant.rs:45:5
+  --> $DIR/large_enum_variant.rs:50:5
    |
 LL |     VariantOk(i32, u32),
    |     ^^^^^^^^^^^^^^^^^^^