Rust: Handle variables introduced in if-let guards

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

@@ -15,21 +15,12 @@ module Impl {
 
   class BlockExprScope extends VariableScope, BlockExpr { }
 
-  abstract class MatchArmScope extends VariableScope {
+  class MatchArmExprScope extends VariableScope {
-    MatchArm arm;
+    MatchArmExprScope() { this = any(MatchArm arm).getExpr() }
-
-    bindingset[arm]
-    MatchArmScope() { exists(arm) }
-
-    Pat getPat() { result = arm.getPat() }
   }
 
-  class MatchArmExprScope extends MatchArmScope {
+  class MatchArmGuardScope extends VariableScope {
-    MatchArmExprScope() { this = arm.getExpr() }
+    MatchArmGuardScope() { this = any(MatchArm arm).getGuard() }
-  }
-
-  class MatchArmGuardScope extends MatchArmScope {
-    MatchArmGuardScope() { this = arm.getGuard() }
   }
 
   class ClosureBodyScope extends VariableScope {
@@ -41,7 +32,7 @@ module Impl {
    *
    * Such variables are only available in the body guarded by the condition.
    */
-  class ConditionScope extends VariableScope, Expr {
+  class ConditionScope extends VariableScope {
     private AstNode parent;
     private AstNode body;
 
@@ -57,6 +48,12 @@ module Impl {
           this = we.getCondition() and
           body = we.getLoopBody()
         )
+      or
+      parent =
+        any(MatchArm ma |
+          this = ma.getGuard() and
+          body = ma.getExpr()
+        )
     }
 
     /** Gets the parent of this condition. */
@@ -417,11 +414,14 @@ module Impl {
       ord = getPreOrderNumbering(scope, scope)
       or
       exists(Pat pat | pat = getAVariablePatAncestor(v) |
-        scope =
+        exists(MatchArm arm |
-          any(MatchArmScope arm |
+          pat = arm.getPat() and
-            arm.getPat() = pat and
+          ord = getPreOrderNumbering(scope, scope)
-            ord = getPreOrderNumbering(scope, arm)
+        |
-          )
+          scope = arm.getGuard()
+          or
+          not arm.hasGuard() and scope = arm.getExpr()
+        )
         or
         exists(LetStmt let |
           let.getPat() = pat and

rust/ql/test/library-tests/variables/Ssa.expected

@@ -96,6 +96,7 @@ definition
 | main.rs:366:18:366:18 | x | main.rs:366:18:366:18 | x |
 | main.rs:373:9:373:9 | x | main.rs:373:9:373:9 | x |
 | main.rs:375:14:375:14 | y | main.rs:375:14:375:14 | y |
+| main.rs:376:25:376:25 | y | main.rs:376:25:376:25 | y |
 | main.rs:384:5:384:6 | a8 | main.rs:384:5:384:6 | a8 |
 | main.rs:386:9:386:10 | b3 | main.rs:386:9:386:10 | b3 |
 | main.rs:387:9:387:10 | c1 | main.rs:387:9:387:10 | c1 |
@@ -288,7 +289,7 @@ read
 | main.rs:366:18:366:18 | x | main.rs:366:18:366:18 | x | main.rs:367:20:367:20 | x |
 | main.rs:373:9:373:9 | x | main.rs:373:9:373:9 | x | main.rs:374:11:374:11 | x |
 | main.rs:375:14:375:14 | y | main.rs:375:14:375:14 | y | main.rs:377:22:377:22 | y |
-| main.rs:375:14:375:14 | y | main.rs:375:14:375:14 | y | main.rs:378:26:378:26 | y |
+| main.rs:376:25:376:25 | y | main.rs:376:25:376:25 | y | main.rs:378:26:378:26 | y |
 | main.rs:384:5:384:6 | a8 | main.rs:384:5:384:6 | a8 | main.rs:390:15:390:16 | a8 |
 | main.rs:386:9:386:10 | b3 | main.rs:386:9:386:10 | b3 | main.rs:391:15:391:16 | b3 |
 | main.rs:387:9:387:10 | c1 | main.rs:387:9:387:10 | c1 | main.rs:392:15:392:16 | c1 |
@@ -479,6 +480,7 @@ firstRead
 | main.rs:366:18:366:18 | x | main.rs:366:18:366:18 | x | main.rs:367:20:367:20 | x |
 | main.rs:373:9:373:9 | x | main.rs:373:9:373:9 | x | main.rs:374:11:374:11 | x |
 | main.rs:375:14:375:14 | y | main.rs:375:14:375:14 | y | main.rs:377:22:377:22 | y |
+| main.rs:376:25:376:25 | y | main.rs:376:25:376:25 | y | main.rs:378:26:378:26 | y |
 | main.rs:384:5:384:6 | a8 | main.rs:384:5:384:6 | a8 | main.rs:390:15:390:16 | a8 |
 | main.rs:386:9:386:10 | b3 | main.rs:386:9:386:10 | b3 | main.rs:391:15:391:16 | b3 |
 | main.rs:387:9:387:10 | c1 | main.rs:387:9:387:10 | c1 | main.rs:392:15:392:16 | c1 |
@@ -587,7 +589,6 @@ adjacentReads
 | main.rs:334:9:334:9 | x | main.rs:334:9:334:9 | x | main.rs:335:11:335:11 | x | main.rs:343:15:343:15 | x |
 | main.rs:348:9:348:9 | x | main.rs:348:9:348:9 | x | main.rs:350:7:350:7 | x | main.rs:355:7:355:7 | x |
 | main.rs:348:9:348:9 | x | main.rs:348:9:348:9 | x | main.rs:355:7:355:7 | x | main.rs:359:19:359:19 | x |
-| main.rs:375:14:375:14 | y | main.rs:375:14:375:14 | y | main.rs:377:22:377:22 | y | main.rs:378:26:378:26 | y |
 | main.rs:402:13:402:15 | a10 | main.rs:402:13:402:15 | a10 | main.rs:406:15:406:17 | a10 | main.rs:415:9:415:11 | a10 |
 | main.rs:403:13:403:14 | b4 | main.rs:403:13:403:14 | b4 | main.rs:407:15:407:16 | b4 | main.rs:416:9:416:10 | b4 |
 | main.rs:404:13:404:14 | c2 | main.rs:404:13:404:14 | c2 | main.rs:408:15:408:16 | c2 | main.rs:417:9:417:10 | c2 |

rust/ql/test/library-tests/variables/main.rs

@@ -375,7 +375,7 @@ fn match_pattern16() {
         Some(y) // y1
             if let Some(y) = // y2
                 Some(y) // $ read_access=y1
-            => print_i64(y), // $ MISSING: read_access=y2 $ SPURIOUS: read_access=y1
+            => print_i64(y), // $ read_access=y2
         _ => {},
     }
 }

rust/ql/test/library-tests/variables/variables.expected

@@ -238,7 +238,7 @@ variableAccess
 | main.rs:367:20:367:20 | x | main.rs:366:18:366:18 | x |
 | main.rs:374:11:374:11 | x | main.rs:373:9:373:9 | x |
 | main.rs:377:22:377:22 | y | main.rs:375:14:375:14 | y |
-| main.rs:378:26:378:26 | y | main.rs:375:14:375:14 | y |
+| main.rs:378:26:378:26 | y | main.rs:376:25:376:25 | y |
 | main.rs:390:15:390:16 | a8 | main.rs:384:5:384:6 | a8 |
 | main.rs:391:15:391:16 | b3 | main.rs:386:9:386:10 | b3 |
 | main.rs:392:15:392:16 | c1 | main.rs:387:9:387:10 | c1 |
@@ -470,7 +470,7 @@ variableReadAccess
 | main.rs:367:20:367:20 | x | main.rs:366:18:366:18 | x |
 | main.rs:374:11:374:11 | x | main.rs:373:9:373:9 | x |
 | main.rs:377:22:377:22 | y | main.rs:375:14:375:14 | y |
-| main.rs:378:26:378:26 | y | main.rs:375:14:375:14 | y |
+| main.rs:378:26:378:26 | y | main.rs:376:25:376:25 | y |
 | main.rs:390:15:390:16 | a8 | main.rs:384:5:384:6 | a8 |
 | main.rs:391:15:391:16 | b3 | main.rs:386:9:386:10 | b3 |
 | main.rs:392:15:392:16 | c1 | main.rs:387:9:387:10 | c1 |