Create rule S7443 Calls to std::mem::transmute should not be evaluated eagerly (#4786)

* Create rule S7443

* Update metadata.json

* Update rule.adoc

* Update metadata.json

---------

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

rules/S7443/metadata.json

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+{
+}

rules/S7443/rust/metadata.json

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+{
+  "title": "Calls to `std::mem::transmute` should not be evaluated eagerly",
+  "type": "BUG",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "5min"
+  },
+  "tags": [
+    "clippy"
+  ],
+  "defaultSeverity": "Critical",
+  "ruleSpecification": "RSPEC-7443",
+  "sqKey": "S7443",
+  "scope": "All",
+  "defaultQualityProfiles": ["Sonar way"],
+  "quickfix": "unknown",
+  "code": {
+    "impacts": {
+      "RELIABILITY": "HIGH"
+    },
+    "attribute": "LOGICAL"
+  }
+}

rules/S7443/rust/rule.adoc

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+
+== Why is this an issue?
+
+When a transmute is placed within an expression that uses eager evaluation (like `bool::then_some`), it will execute even if a preceding validity check fails. This can result in creating invalid values, potentially leading to undefined behavior.
+
+
+== How to fix it
+
+Use lazy evaluation (for example by replacing `then_some` with `then`) and providing a closure that contains the transmute. This ensures the transmute only occurs if the validity check passes.
+
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,rust,diff-id=1,diff-type=noncompliant]
+----
+#[repr(u8)]
+enum Opcode {
+    Add = 0,
+    Sub = 1,
+    Mul = 2,
+    Div = 3
+}
+
+fn int_to_opcode(op: u8) -> Option<Opcode> {
+    (op < 4).then_some(unsafe { std::mem::transmute(op) })
+}
+----
+
+==== Compliant solution
+
+[source,rust,diff-id=1,diff-type=compliant]
+----
+#[repr(u8)]
+enum Opcode {
+    Add = 0,
+    Sub = 1,
+    Mul = 2,
+    Div = 3
+}
+
+fn int_to_opcode(op: u8) -> Option<Opcode> {
+    (op < 4).then(|| unsafe { std::mem::transmute(op) })
+}
+----
+
+== Resources
+=== Documentation
+
+* Clippy Lints - https://rust-lang.github.io/rust-clippy/master/index.html#eager_transmute
+