Test data-structure sizes in 32-bit Windows on CI, and fix size_of_hasher

.github/workflows/ci.yml

@@ -309,6 +309,24 @@ jobs:
           GIX_TEST_IGNORE_ARCHIVES: '1'
         run: cargo nextest run --workspace --no-fail-fast
 
+  test-32bit-windows-size:
+    runs-on: windows-latest
+
+    env:
+      TARGET: i686-pc-windows-msvc
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: ${{ env.TARGET }}
+      - uses: Swatinem/rust-cache@v2
+      - uses: taiki-e/install-action@v2
+        with:
+          tool: nextest
+      - name: Test (nextest)
+        run: cargo nextest run --target $env:TARGET --workspace --no-fail-fast size
+
   lint:
     runs-on: ubuntu-latest
 
@@ -504,6 +522,7 @@ jobs:
       - test-fast
       - test-fixtures-windows
       - test-32bit
+      - test-32bit-windows-size
       - lint
       - cargo-deny
       - check-packetline

gix-hash/tests/hash/hasher.rs

@@ -1,12 +1,15 @@
 use gix_hash::{Hasher, ObjectId};
+use gix_testtools::size_ok;
 
 #[test]
 fn size_of_hasher() {
-    assert_eq!(
-        std::mem::size_of::<Hasher>(),
-        if cfg!(target_arch = "x86") { 820 } else { 824 },
-        "The size of this type may be relevant when hashing millions of objects,\
-        and shouldn't change unnoticed. The DetectionState alone clocks in at 724 bytes."
+    let actual = std::mem::size_of::<Hasher>();
+    let expected = 824;
+    assert!(
+        size_ok(actual, expected),
+        "The size of this type may be relevant when hashing millions of objects, and shouldn't\
+        change unnoticed: {actual} <~ {expected}\
+        (The DetectionState alone clocked in at 724 bytes when last examined.)"
     );
 }