Add test to prevent regression for fields display

tests/rustdoc-gui/fields.goml

@@ -0,0 +1,18 @@
+// This test checks that fields are displayed as expected (one by line).
+go-to: "file://" + |DOC_PATH| + "/test_docs/fields/struct.Struct.html"
+store-position: ("#structfield\.a", {"y": a_y})
+store-position: ("#structfield\.b", {"y": b_y})
+assert: |a_y| < |b_y|
+
+go-to: "file://" + |DOC_PATH| + "/test_docs/fields/union.Union.html"
+store-position: ("#structfield\.a", {"y": a_y})
+store-position: ("#structfield\.b", {"y": b_y})
+assert: |a_y| < |b_y|
+
+go-to: "file://" + |DOC_PATH| + "/test_docs/fields/enum.Enum.html"
+store-position: ("#variant\.A\.field\.a", {"y": a_y})
+store-position: ("#variant\.A\.field\.b", {"y": b_y})
+assert: |a_y| < |b_y|
+store-position: ("#variant\.B\.field\.a", {"y": a_y})
+store-position: ("#variant\.B\.field\.b", {"y": b_y})
+assert: |a_y| < |b_y|

tests/rustdoc-gui/src/test_docs/lib.rs

@@ -486,3 +486,24 @@ macro_rules! foo {
     }
 
 }
+
+pub mod fields {
+    pub struct Struct {
+        pub a: u8,
+        pub b: u32,
+    }
+    pub union Union {
+        pub a: u8,
+        pub b: u32,
+    }
+    pub enum Enum {
+        A {
+            a: u8,
+            b: u32,
+        },
+        B {
+            a: u8,
+            b: u32,
+        },
+    }
+}

tests/rustdoc/union-fields-html.rs

@@ -0,0 +1,11 @@
+#![crate_name = "foo"]
+
+// @has 'foo/union.Union.html'
+// Checking that there is a whitespace after `:`.
+// @has - '//*[@id="structfield.a"]/code' 'a: u8'
+// @has - '//*[@id="structfield.b"]/code' 'b: u32'
+pub union Union {
+    pub a: u8,
+    /// tadam
+    pub b: u32,
+}