Create rule S1764: Identical expressions should not be used on both sides of a binary operator (#4681)

* Add rust to rule S1764

* Add rule description

* Whitespace

* Update metadata.json

* Fix JSON syntax

* Update rule.adoc

* Update rule.adoc

---------

Co-authored-by: sallaigy <sallaigy@users.noreply.github.com>
Co-authored-by: Gyula Sallai <gyula.sallai@sonarsource.com>

rules/S1764/rust/metadata.json

@@ -0,0 +1,7 @@
+{
+  "title": "Identical expressions should not be used on both sides of a binary operator",
+  "tags": [
+    "cert",
+    "clippy"
+  ]
+}

rules/S1764/rust/rule.adoc

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+== Why is this an issue?
+
+Using the same value on either side of a binary operator is almost always a mistake. In the case of logical operators, it is either a copy/paste error and therefore a bug, or it is simply wasted code, and should be simplified. In the case of bitwise operators and most binary mathematical operators, having the same value on both sides of an operator yields predictable results, and should be simplified.
+
+=== Noncompliant code example
+
+[source,rust]
+----
+if a == a { // always true
+  doZ();
+}
+if a != a  { // always false
+  doY();
+}
+
+assert_eq!(a, a); // always true
+----
+
+== Resources
+=== Documentation
+
+* Clippy Lints - https://rust-lang.github.io/rust-clippy/master/index.html#eq_op
+
+ifdef::env-github,rspecator-view[]
+
+'''
+== Implementation Specification
+(visible only on this page)
+
+include::../message.adoc[]
+
+include::../highlighting.adoc[]
+
+'''
+== Comments And Links
+(visible only on this page)
+
+include::../comments-and-links.adoc[]
+
+endif::env-github,rspecator-view[]