Rust: Fix CFG for while let loops

Author: hvitved

rust/ql/lib/codeql/rust/controlflow/internal/ControlFlowGraphImpl.qll

@@ -193,7 +193,7 @@ class IfExprTree extends PostOrderTree instanceof IfExpr {
     child = [super.getCondition(), super.getThen(), super.getElse()]
   }
 
-  ConditionalCompletion conditionCompletion(Completion c) {
+  private ConditionalCompletion conditionCompletion(Completion c) {
     if super.getCondition() instanceof LetExpr
     then result = c.(MatchCompletion)
     else result = c.(BooleanCompletion)
@@ -345,15 +345,21 @@ class WhileExprTree extends LoopingExprTree instanceof WhileExpr {
 
   override predicate first(AstNode node) { first(super.getCondition(), node) }
 
+  private ConditionalCompletion conditionCompletion(Completion c) {
+    if super.getCondition() instanceof LetExpr
+    then result = c.(MatchCompletion)
+    else result = c.(BooleanCompletion)
+  }
+
   override predicate succ(AstNode pred, AstNode succ, Completion c) {
     super.succ(pred, succ, c)
     or
     last(super.getCondition(), pred, c) and
-    c.(BooleanCompletion).succeeded() and
+    this.conditionCompletion(c).succeeded() and
     first(this.getLoopBody(), succ)
     or
     last(super.getCondition(), pred, c) and
-    c.(BooleanCompletion).failed() and
+    this.conditionCompletion(c).failed() and
     succ = this
   }
 

rust/ql/test/library-tests/controlflow/Cfg.expected

@@ -123,12 +123,26 @@
 | test.rs:61:13:61:22 | ExprStmt | test.rs:61:13:61:13 | PathExpr |  |
 | test.rs:61:17:61:21 | false | test.rs:61:13:61:21 | ... = ... |  |
 | test.rs:65:5:72:5 | enter test_while_let | test.rs:66:9:66:29 | LetStmt |  |
+| test.rs:65:5:72:5 | exit test_while_let (normal) | test.rs:65:5:72:5 | exit test_while_let |  |
+| test.rs:65:25:72:5 | BlockExpr | test.rs:65:5:72:5 | exit test_while_let (normal) |  |
 | test.rs:66:9:66:29 | LetStmt | test.rs:66:24:66:24 | 1 |  |
 | test.rs:66:13:66:20 | iter | test.rs:67:15:67:39 | LetExpr | match, no-match |
 | test.rs:66:24:66:24 | 1 | test.rs:66:27:66:28 | 10 |  |
 | test.rs:66:24:66:28 | RangeExpr | test.rs:66:13:66:20 | iter |  |
 | test.rs:66:27:66:28 | 10 | test.rs:66:24:66:28 | RangeExpr |  |
+| test.rs:67:9:71:9 | WhileExpr | test.rs:65:25:72:5 | BlockExpr |  |
 | test.rs:67:15:67:39 | LetExpr | test.rs:67:19:67:25 | TupleStructPat |  |
+| test.rs:67:19:67:25 | TupleStructPat | test.rs:67:9:71:9 | WhileExpr | no-match |
+| test.rs:67:19:67:25 | TupleStructPat | test.rs:68:17:68:17 | PathExpr | match |
+| test.rs:67:41:71:9 | BlockExpr | test.rs:67:15:67:39 | LetExpr |  |
+| test.rs:68:13:70:13 | IfExpr | test.rs:67:41:71:9 | BlockExpr |  |
+| test.rs:68:16:68:22 | ParenExpr | test.rs:68:13:70:13 | IfExpr | false |
+| test.rs:68:16:68:22 | ParenExpr | test.rs:69:17:69:22 | ExprStmt | true |
+| test.rs:68:17:68:17 | PathExpr | test.rs:68:21:68:21 | 5 |  |
+| test.rs:68:17:68:21 | ... = ... | test.rs:68:16:68:22 | ParenExpr |  |
+| test.rs:68:21:68:21 | 5 | test.rs:68:17:68:21 | ... = ... |  |
+| test.rs:69:17:69:21 | BreakExpr | test.rs:67:9:71:9 | WhileExpr | break |
+| test.rs:69:17:69:22 | ExprStmt | test.rs:69:17:69:21 | BreakExpr |  |
 | test.rs:74:5:81:5 | enter test_for | test.rs:75:18:75:18 | 0 |  |
 | test.rs:74:5:81:5 | exit test_for (normal) | test.rs:74:5:81:5 | exit test_for |  |
 | test.rs:74:25:81:5 | BlockExpr | test.rs:74:5:81:5 | exit test_for (normal) |  |