Merge pull request #17913 from geoffw0/unusedvar8

Rust: Fix rust/unused-variable FPs

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

@@ -87,7 +87,9 @@ module Impl {
     not name.charAt(0).isUppercase() and
     // exclude parameters from functions without a body as these are trait method declarations
     // without implementations
-    not exists(Function f | not f.hasBody() and f.getParamList().getAParam().getPat() = p)
+    not exists(Function f | not f.hasBody() and f.getParamList().getAParam().getPat() = p) and
+    // exclude parameters from function pointer types (e.g. `x` in `fn(x: i32) -> i32`)
+    not exists(FnPtrType fp | fp.getParamList().getParam(_).getPat() = p)
   }
 
   /** A variable. */

rust/ql/src/queries/unusedentities/UnusedVariable.ql

@@ -12,5 +12,8 @@ import rust
 import UnusedVariable
 
 from Variable v
-where isUnused(v)
+where
+  isUnused(v) and
+  not isAllowableUnused(v) and
+  not v instanceof DiscardVariable
 select v, "Variable '" + v + "' is not used."

rust/ql/src/queries/unusedentities/UnusedVariable.qll

@@ -1,14 +1,26 @@
 import rust
 
-/** A deliberately unused variable. */
+/**
+ * A deliberately unused variable, for example `_` or `_x`.
+ */
 class DiscardVariable extends Variable {
   DiscardVariable() { this.getName().charAt(0) = "_" }
 }
 
-/** Holds if variable `v` is unused. */
+/**
+ * Holds if variable `v` is unused.
+ */
 predicate isUnused(Variable v) {
+  // variable is not accessed or initialized
   not exists(v.getAnAccess()) and
-  not exists(v.getInitializer()) and
-  not v instanceof DiscardVariable and
-  not v.getPat().isInMacroExpansion()
+  not exists(v.getInitializer())
+}
+
+/**
+ * Holds if variable `v` is in a context where we may not find a use for it,
+ * but that's expected and should not be considered a problem.
+ */
+predicate isAllowableUnused(Variable v) {
+  // in a macro expansion
+  v.getPat().isInMacroExpansion()
 }

rust/ql/test/query-tests/unusedentities/CONSISTENCY/DataFlowConsistency.expected

@@ -1,85 +1,100 @@
 uniqueEnclosingCallable
-| main.rs:382:19:382:21 | Param | Node should have one enclosing callable but has 0. |
-| main.rs:430:29:430:38 | Param | Node should have one enclosing callable but has 0. |
-| main.rs:430:41:430:56 | Param | Node should have one enclosing callable but has 0. |
+| main.rs:392:19:392:21 | Param | Node should have one enclosing callable but has 0. |
+| main.rs:440:29:440:38 | Param | Node should have one enclosing callable but has 0. |
+| main.rs:440:41:440:56 | Param | Node should have one enclosing callable but has 0. |
+| main.rs:493:16:493:18 | Param | Node should have one enclosing callable but has 0. |
+| main.rs:494:16:494:21 | Param | Node should have one enclosing callable but has 0. |
+| main.rs:495:16:496:25 | Param | Node should have one enclosing callable but has 0. |
+| main.rs:496:12:496:17 | Param | Node should have one enclosing callable but has 0. |
+| main.rs:499:18:499:23 | Param | Node should have one enclosing callable but has 0. |
+| main.rs:502:24:502:29 | Param | Node should have one enclosing callable but has 0. |
 | more.rs:4:23:4:28 | Param | Node should have one enclosing callable but has 0. |
 | more.rs:8:19:8:24 | Param | Node should have one enclosing callable but has 0. |
 uniqueCallEnclosingCallable
-| main.rs:11:13:11:29 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:12:13:12:29 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:16:14:16:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:18:8:18:13 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:19:18:19:28 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:22:14:22:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:23:5:23:19 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:23:5:23:19 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:41:14:41:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:45:8:45:13 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:50:14:50:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:53:8:53:13 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:58:14:58:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:62:14:62:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:67:12:67:17 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:68:12:68:17 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:13:13:13:29 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:14:13:14:29 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:18:14:18:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:20:8:20:13 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:21:18:21:28 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:24:14:24:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:25:5:25:19 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:25:5:25:19 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:43:14:43:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:47:8:47:13 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:52:14:52:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:55:8:55:13 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:60:14:60:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:64:14:64:24 | CallExpr | Call should have one enclosing callable but has 0. |
 | main.rs:69:12:69:17 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:70:14:70:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:96:14:96:45 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:99:14:99:38 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:70:12:70:17 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:71:12:71:17 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:72:14:72:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:98:14:98:45 | CallExpr | Call should have one enclosing callable but has 0. |
 | main.rs:101:14:101:38 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:114:14:114:32 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:117:18:117:33 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:174:18:174:29 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:178:18:178:31 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:182:18:182:37 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:187:22:187:33 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:192:18:192:27 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:196:21:196:30 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:196:21:196:30 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:200:18:200:38 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:204:9:204:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:204:9:204:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:208:9:208:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:213:9:213:32 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:213:20:213:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:213:27:213:31 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:240:22:240:29 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:243:22:243:29 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:247:20:247:27 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:254:21:254:28 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:260:13:260:20 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:267:13:267:20 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:275:13:275:28 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:282:13:282:30 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:289:31:289:37 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:337:21:337:51 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:338:5:338:39 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:340:58:340:92 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:340:61:340:91 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:343:22:343:59 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:346:22:346:29 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:396:13:396:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:400:13:400:22 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:460:9:464:10 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:471:5:471:14 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:472:5:472:14 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:473:5:473:13 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:474:5:474:12 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:475:5:475:13 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:476:14:476:54 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:476:36:476:54 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:477:5:477:11 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:478:5:478:21 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:479:5:479:15 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:480:5:480:15 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:481:5:481:24 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:483:5:483:22 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:485:5:485:23 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:487:5:487:23 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:488:5:488:23 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:489:5:489:23 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:490:5:490:22 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:491:5:491:22 | CallExpr | Call should have one enclosing callable but has 0. |
-| main.rs:493:5:493:12 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:103:14:103:38 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:116:14:116:32 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:119:18:119:33 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:176:18:176:29 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:180:18:180:31 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:184:18:184:37 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:189:22:189:33 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:194:18:194:27 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:198:21:198:30 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:198:21:198:30 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:202:21:202:32 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:202:21:202:32 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:206:21:206:30 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:206:21:206:30 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:210:18:210:38 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:214:9:214:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:214:9:214:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:218:9:218:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:223:9:223:32 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:223:20:223:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:223:27:223:31 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:250:22:250:29 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:253:22:253:29 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:257:20:257:27 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:264:21:264:28 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:270:13:270:20 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:277:13:277:20 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:285:13:285:28 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:292:13:292:30 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:299:31:299:37 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:347:21:347:51 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:348:5:348:39 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:350:58:350:92 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:350:61:350:91 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:353:22:353:59 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:356:22:356:29 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:406:13:406:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:410:13:410:22 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:470:9:474:10 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:487:5:487:21 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:487:5:487:21 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:508:5:508:14 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:509:5:509:14 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:510:5:510:13 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:511:5:511:12 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:512:5:512:13 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:513:14:513:54 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:513:36:513:54 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:514:5:514:11 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:515:5:515:21 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:516:5:516:15 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:517:5:517:15 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:518:5:518:24 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:519:5:519:12 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:520:5:520:16 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:522:5:522:14 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:523:5:523:14 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:525:5:525:22 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:527:5:527:23 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:529:5:529:23 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:530:5:530:23 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:531:5:531:23 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:532:5:532:22 | CallExpr | Call should have one enclosing callable but has 0. |
+| main.rs:533:5:533:22 | CallExpr | Call should have one enclosing callable but has 0. |
 | more.rs:45:14:45:26 | CallExpr | Call should have one enclosing callable but has 0. |
 | more.rs:46:14:46:25 | CallExpr | Call should have one enclosing callable but has 0. |
 | more.rs:47:14:47:26 | CallExpr | Call should have one enclosing callable but has 0. |