Fix RULE-7-0-2 false positives for contextual bool conversions

NoImplicitBoolConversion reported contextual conversions that the rule
permits:

- Condition declarations (if (T* p = f()), while (auto sp = w.lock()),
  for (...; T* p = f(); ...)): the initializer is contextually converted
  to bool. Treat the initializer of a condition declaration as a
  contextual bool context, so pointers and classes with an explicit
  operator bool are no longer flagged.
- static_cast<bool>(x) where x is a class (or class template
  instantiation) with an explicit operator bool: the extractor leaves
  members of uninstantiated templates unresolved, so look the operator up
  on the instantiated template as well.

Author: castler

change_notes/2026-10-23-fix-fp-rule-7-0-2-contextual-conversions.md

@@ -0,0 +1,7 @@
+- `RULE-7-0-2` - `NoImplicitBoolConversion.ql`:
+   - Fixed false positives on the initializer of an `if`/`for` condition
+     declaration (e.g. `if (T* p = f())` or `if (auto sp = weak.lock())`) when
+     the initialized type is a pointer or a class with an explicit
+     `operator bool`. These are contextual conversions, which are permitted.
+   - Fixed false positives on `static_cast<bool>` of a class type with an
+     explicit `operator bool` inside a class template.

cpp/misra/src/rules/RULE-7-0-2/NoImplicitBoolConversion.ql

@@ -16,6 +16,21 @@
 import cpp
 import codingstandards.cpp.misra
 
+/**
+ * The initializer of a condition declaration is contextually converted to bool, e.g.
+ * `if (T* p = f())` or `if (auto sp = weak.lock())`.
+ */
+predicate isInConditionDeclarationInitializer(Expr expr) {
+  exists(ConditionDeclExpr condDecl |
+    condDecl.getExpr() = expr and
+    (
+      exists(IfStmt ifStmt | ifStmt.getCondition() = condDecl) or
+      exists(WhileStmt whileStmt | whileStmt.getCondition() = condDecl) or
+      exists(ForStmt forStmt | forStmt.getCondition() = condDecl)
+    )
+  )
+}
+
 predicate isInContextualBoolContext(Expr expr) {
   exists(IfStmt ifStmt | ifStmt.getCondition() = expr) or
   exists(WhileStmt whileStmt | whileStmt.getCondition() = expr) or
@@ -24,7 +39,8 @@ predicate isInContextualBoolContext(Expr expr) {
   exists(ConditionalExpr condExpr | condExpr.getCondition() = expr) or
   exists(LogicalAndExpr logicalAnd | logicalAnd.getAnOperand() = expr) or
   exists(LogicalOrExpr logicalOr | logicalOr.getAnOperand() = expr) or
-  exists(NotExpr notExpr | notExpr.getOperand() = expr)
+  exists(NotExpr notExpr | notExpr.getOperand() = expr) or
+  isInConditionDeclarationInitializer(expr)
 }
 
 predicate isInWhileConditionDeclaration(Expr expr) {
@@ -88,6 +104,20 @@ where
         // an array to a pointer, then the pointer to bool
         isInContextualBoolContext(conv.getUnconverted())
       ) and
+      // Exception 1: Static cast to bool from a class with an explicit operator bool. In an
+      // uninstantiated template the cast has no resolved call to the conversion operator, so it
+      // appears only as a `Conversion` from the class type.
+      not (
+        conv instanceof StaticCast and
+        exists(ConversionOperator op |
+          op.isExplicit() and
+          op.getType().getUnspecifiedType() instanceof BoolType and
+          exists(Class source | source = conv.getExpr().getType().getUnspecifiedType() |
+            op = source.getAMember() or
+            op = source.(ClassTemplateInstantiation).getTemplate().getAMember()
+          )
+        )
+      ) and
       // Exception 3: Unconverted expression is a bit-field of size 1
       not isBitFieldOfSizeOne(conv.getUnconverted()) and
       // Exception 4: Unconverted expression is in a while condition declaration

cpp/misra/test/rules/RULE-7-0-2/NoImplicitBoolConversion.expected

@@ -25,3 +25,4 @@
 | test.cpp:201:13:201:14 | (bool)... | Conversion from 'int32_t *' to 'bool'. |
 | test.cpp:213:13:213:14 | (bool)... | Conversion from '..:: *' to 'bool'. |
 | test.cpp:214:13:214:14 | (bool)... | Conversion from '..:: *' to 'bool'. |
+| test.cpp:283:20:283:21 | (bool)... | Conversion from 'int32_t' to 'bool'. |

cpp/misra/test/rules/RULE-7-0-2/test.cpp

@@ -268,4 +268,34 @@ constexpr bool derived_from_template_v = is_something_v<T>; // COMPLIANT
 
 bool test_dependent_variable_template_instantiation() {
   return derived_from_template_v<std::int32_t>; // COMPLIANT
-}
+}
+void test_condition_declaration() {
+  if (std::int32_t *l1 = f3()) { // COMPLIANT - exception #2
+  }
+  if (auto *const l2 = f3()) { // COMPLIANT - exception #2
+  }
+  while (std::int32_t *l3 = f3()) { // COMPLIANT - exception #2
+  }
+  if (TestClassExplicit l4 = TestClassExplicit{}) { // COMPLIANT
+  }
+  if (std::int32_t *l5 = f3(); l5) { // COMPLIANT - exception #2
+  }
+  if (std::int32_t l6 = f1()) { // NON_COMPLIANT
+  }
+}
+
+template <typename T> class TestTemplateExplicit {
+public:
+  explicit operator bool() const { return true; }
+};
+
+template <typename T>
+bool test_static_cast_template(const TestTemplateExplicit<T> &l1) {
+  return !static_cast<bool>(l1); // COMPLIANT - exception #1
+}
+
+bool test_static_cast_template_use(
+    const TestTemplateExplicit<std::int32_t> &l1) {
+  bool l2 = static_cast<bool>(l1); // COMPLIANT - exception #1
+  return l2 && test_static_cast_template(l1);
+}