Rust: Restrict variables to lowercase (for now).

Author: geoffw0

rust/ql/lib/codeql/rust/elements/internal/VariableImpl.qll

@@ -85,7 +85,13 @@ module Impl {
     private AstNode definingNode;
     private string name;
 
-    Variable() { this = MkVariable(definingNode, name) }
+    Variable() {
+      this = MkVariable(definingNode, name) and
+      // exclude for now anything starting with an uppercase character, which may be an enum constant (e.g. `None`). This excludes
+      // static and constant variables (UPPERCASE), which we don't appear to recognize yet anyway. This also assumes programmers
+      // follow the naming guidelines, which they generally do, but they're not enforced.
+      not name.charAt(0).isUppercase()
+    }
 
     /** Gets the name of this variable. */
     string getName() { result = name }

rust/ql/test/query-tests/unusedentities/UnusedVariable.expected

@@ -8,15 +8,10 @@
 | main.rs:202:17:202:17 | a | Variable is not used. |
 | main.rs:210:20:210:22 | val | Variable is not used. |
 | main.rs:223:14:223:16 | val | Variable is not used. |
-| main.rs:225:9:225:12 | None | Variable is not used. |
-| main.rs:234:9:234:12 | None | Variable is not used. |
 | main.rs:240:22:240:24 | val | Variable is not used. |
 | main.rs:248:24:248:26 | val | Variable is not used. |
 | main.rs:257:13:257:15 | num | Variable is not used. |
-| main.rs:268:9:268:11 | Yes | Variable is not used. |
-| main.rs:269:9:269:10 | No | Variable is not used. |
 | main.rs:272:12:272:12 | j | Variable is not used. |
-| main.rs:282:12:282:14 | Yes | Variable is not used. |
 | main.rs:294:25:294:25 | y | Variable is not used. |
 | main.rs:298:28:298:28 | a | Variable is not used. |
 | main.rs:302:9:302:9 | p | Variable is not used. |

rust/ql/test/query-tests/unusedentities/main.rs

@@ -222,7 +222,7 @@ fn if_lets_matches() {
     match c {
         Some(val) => { // BAD: unused variable
         }
-        None => { // SPURIOUS: unused variable 'None'
+        None => {
         }
     }
 
@@ -231,7 +231,7 @@ fn if_lets_matches() {
         Some(val) => {
             total += val;
         }
-        None => { // SPURIOUS: unused variable 'None'
+        None => {
         }
     }
 
@@ -265,8 +265,8 @@ fn if_lets_matches() {
 
     let i = Yes;
     match i {
-        Yes => {} // SPURIOUS: unused variable 'Yes'
-        No => {} // SPURIOUS: unused variable 'No'
+        Yes => {}
+        No => {}
     }
 
     if let j = Yes { // BAD: unused variable
@@ -279,7 +279,7 @@ fn if_lets_matches() {
     }
 
     let l = Yes;
-    if let Yes = l { // SPURIOUS: unused variable 'Yes'
+    if let Yes = l {
     }
 
     match 1 {