Enumerate and indent the descriptions of the inner matchers in elements_are!, unordered_elements_are!, and friends.

This makes a test failure assertion a bit more readable, by visually separating the inner matchers from the rest of the message. The enumeration also helps the reader to connect the mismatch explanation below with the expected values indicated in the matcher descriptions.

PiperOrigin-RevId: 505621887

Author: hovinenb

googletest/src/matchers/elements_are_matcher.rs

@@ -106,7 +106,11 @@ pub mod internal {
                 matcher_result.pick("has", "doesn't have"),
                 self.elements
                     .iter()
-                    .map(|m| m.describe(MatcherResult::Matches))
+                    .enumerate()
+                    .map(|(index, matcher)| format!(
+                        "    {index}: {}",
+                        matcher.describe(MatcherResult::Matches)
+                    ))
                     .collect::<Vec<_>>()
                     .join("\n")
             )
@@ -151,9 +155,9 @@ mod tests {
                 "\
 Value of: vec![1, 4, 3]
 Expected: has elements:
-is equal to 1
-is equal to 2
-is equal to 3
+    0: is equal to 1
+    1: is equal to 2
+    2: is equal to 3
 Actual: [
     1,
     4,

googletest/src/matchers/unordered_elements_are_matcher.rs

@@ -327,7 +327,11 @@ pub mod internal {
                 matcher_result.pick("contains", "doesn't contain"),
                 self.elements
                     .iter()
-                    .map(|&m| m.describe(MatcherResult::Matches))
+                    .enumerate()
+                    .map(|(index, matcher)| format!(
+                        "    {index}: {}",
+                        matcher.describe(MatcherResult::Matches)
+                    ))
                     .collect::<Vec<_>>()
                     .join("\n")
             )
@@ -755,9 +759,9 @@ mod tests {
                 "\
 Value of: vec![1, 4, 3]
 Expected: contains elements matching in any order:
-is equal to 1
-is equal to 2
-is equal to 3
+    0: is equal to 1
+    1: is equal to 2
+    2: is equal to 3
 Actual: [
     1,
     4,