Rust: Restrict 'unreachable' to nodes intended to be part of the CFG.

Author: geoffw0

rust/ql/src/queries/unusedentities/UnreachableCode.ql

@@ -17,7 +17,12 @@ import codeql.rust.controlflow.internal.ControlFlowGraphImpl as ControlFlowGraph
  */
 private predicate unreachable(AstNode n) {
   not n = any(CfgNode cfn).getAstNode() and // reachable nodes
-  n instanceof ControlFlowGraphImpl::ControlFlowTree // part of the CFG
+  exists(ControlFlowGraphImpl::ControlFlowTree cft |
+    // nodes intended to be part of the CFG
+    cft.succ(n, _, _)
+    or
+    cft.succ(_, n, _)
+  )
 }
 
 /**

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

@@ -1,31 +1,14 @@
-| main.rs:216:9:217:9 | MatchArm | This code is never reached. |
-| main.rs:218:9:219:9 | MatchArm | This code is never reached. |
-| main.rs:224:9:226:9 | MatchArm | This code is never reached. |
-| main.rs:227:9:228:9 | MatchArm | This code is never reached. |
-| main.rs:233:9:234:9 | MatchArm | This code is never reached. |
-| main.rs:235:9:235:28 | MatchArm | This code is never reached. |
-| main.rs:240:9:240:26 | MatchArm | This code is never reached. |
-| main.rs:241:9:241:25 | MatchArm | This code is never reached. |
 | unreachable.rs:12:3:12:17 | ExprStmt | This code is never reached. |
 | unreachable.rs:20:3:20:17 | ExprStmt | This code is never reached. |
 | unreachable.rs:32:3:32:17 | ExprStmt | This code is never reached. |
 | unreachable.rs:39:3:39:17 | ExprStmt | This code is never reached. |
-| unreachable.rs:46:6:46:8 | ParenExpr | This code is never reached. |
-| unreachable.rs:48:7:48:10 | ParenExpr | This code is never reached. |
 | unreachable.rs:60:2:60:16 | ExprStmt | This code is never reached. |
 | unreachable.rs:101:3:101:17 | ExprStmt | This code is never reached. |
 | unreachable.rs:109:3:109:17 | ExprStmt | This code is never reached. |
-| unreachable.rs:117:3:119:3 | MatchArm | This code is never reached. |
-| unreachable.rs:120:3:122:3 | MatchArm | This code is never reached. |
 | unreachable.rs:124:2:124:16 | ExprStmt | This code is never reached. |
-| unreachable.rs:127:3:129:3 | MatchArm | This code is never reached. |
-| unreachable.rs:130:3:132:3 | MatchArm | This code is never reached. |
 | unreachable.rs:134:2:134:16 | ExprStmt | This code is never reached. |
 | unreachable.rs:141:3:141:17 | ExprStmt | This code is never reached. |
 | unreachable.rs:150:4:150:18 | ExprStmt | This code is never reached. |
 | unreachable.rs:156:3:156:17 | ExprStmt | This code is never reached. |
 | unreachable.rs:162:4:162:18 | ExprStmt | This code is never reached. |
 | unreachable.rs:165:2:165:16 | ExprStmt | This code is never reached. |
-| unreachable.rs:171:10:171:16 | ParenExpr | This code is never reached. |
-| unreachable.rs:171:11:171:15 | ParenExpr | This code is never reached. |
-| unreachable.rs:171:12:171:14 | ParenExpr | This code is never reached. |

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

@@ -213,32 +213,32 @@ fn if_lets() {
 
     let c = Some(60);
     match c {
-        Some(val) => { // BAD: unused variable SPURIOUS: unreachable
+        Some(val) => { // BAD: unused variable
         }
-        None => { // SPURIOUS: unused variable 'None', unreachable
+        None => { // SPURIOUS: unused variable 'None'
         }
     }
 
     let d = Some(70);
     match d {
-        Some(val) => { // SPURIOUS: unreachable
+        Some(val) => {
             total += val;
         }
-        None => { // SPURIOUS: unused variable 'None', unreachable
+        None => { // SPURIOUS: unused variable 'None'
         }
     }
 
     let e = MyOption::Some(80);
     match e {
-        MyOption::Some(val) => { // BAD: unused variable, unreachable
+        MyOption::Some(val) => { // BAD: unused variable
         }
-        MyOption::None => {} // SPURIOUS: unreachable
+        MyOption::None => {}
     }
 
     let f = YesOrNo::Yes;
     match f {
-        YesOrNo::Yes => {} // SPURIOUS: unreachable
-        YesOrNo::No => {} // SPURIOUS: unreachable
+        YesOrNo::Yes => {}
+        YesOrNo::No => {}
     }
 }
 

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

@@ -43,9 +43,9 @@ fn unreachable_if() {
 	if cond() {
 		let x = cond();
 
-		if (x) { // SPURIOUS: unreachable
+		if (x) {
 			do_something();
-			if (!x) { // SPURIOUS: unreachable
+			if (!x) {
 				do_something(); // BAD: unreachable code [NOT DETECTED]
 			}
 			do_something();
@@ -114,20 +114,20 @@ fn unreachable_panic() {
 
 fn unreachable_match() {
 	match get_a_number() {
-		1=>{ // [unreachable FALSE POSITIVE]
+		1=>{
 			return;
 		}
-		_=>{ // [unreachable FALSE POSITIVE]
+		_=>{
 			do_something();
 		}
 	}
 	do_something(); // [unreachable FALSE POSITIVE]
 
 	match get_a_number() {
-		1=>{ // [unreachable FALSE POSITIVE]
+		1=>{
 			return;
 		}
-		_=>{ // [unreachable FALSE POSITIVE]
+		_=>{
 			return;
 		}
 	}
@@ -168,5 +168,5 @@ fn unreachable_loop() {
 }
 
 fn unreachable_paren() {
-	let _ = (((1))); // SPURIOUS: unreachable (x3)
+	let _ = (((1)));
 }