Add a test to detect overlapping entries in overview tables

Detects rust-lang#88545

Author: dns2utf8

src/test/rustdoc-gui/huge-collection-of-constants.goml

@@ -0,0 +1,5 @@
+goto: file://|DOC_PATH|/test_docs/huge_amount_of_consts/index.html
+
+// Make sure that the last two entries are more than 12 pixels apart and not stacked on each other.
+
+compare-elements-position-near-false: ("//*[@class='item-table']//div[last()-1]", "//*[@class='item-table']//div[last()-3]", {"y": 12})

src/test/rustdoc-gui/src/test_docs/Cargo.toml

@@ -3,5 +3,7 @@ name = "test_docs"
 version = "0.1.0"
 edition = "2018"
 
+build = "build.rs"
+
 [lib]
 path = "lib.rs"

src/test/rustdoc-gui/src/test_docs/build.rs

@@ -0,0 +1,15 @@
+//! generate 2000 constants for testing
+
+use std::{fs::write, path::PathBuf};
+
+fn main() -> std::io::Result<()> {
+    let out_dir = std::env::var("OUT_DIR").expect("OUT_DIR is not defined");
+
+    let mut output = String::new();
+    for i in 0..2000 {
+        let line = format!("/// Some const A{0}\npub const A{0}: isize = 0;\n", i);
+        output.push_str(&*line);
+    };
+
+    write(&[&*out_dir, "huge_amount_of_consts.rs"].iter().collect::<PathBuf>(), output)
+}

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

@@ -116,3 +116,7 @@ pub mod keyword {}
 
 /// Just some type alias.
 pub type SomeType = u32;
+
+pub mod huge_amount_of_consts {
+    include!(concat!(env!("OUT_DIR"), "/huge_amount_of_consts.rs"));
+}