Merge pull request #77491 from slavapestov/fix-rdar139237671

Sema: Allow closure parameter lists to reference opaque parameter declarations

Author: slavapestov

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -4280,48 +4280,50 @@ void TypeChecker::checkParameterList(ParameterList *params,
     }
 
     // Opaque types cannot occur in parameter position.
-    Type interfaceType = param->getInterfaceType();
-    if (interfaceType->hasTypeParameter()) {
-      interfaceType.findIf([&](Type type) {
-        if (auto fnType = type->getAs<FunctionType>()) {
-          for (auto innerParam : fnType->getParams()) {
-            auto paramType = innerParam.getPlainType();
-            if (!paramType->hasTypeParameter())
-              continue;
-
-            bool hadError = paramType.findIf([&](Type innerType) {
-              auto genericParam = innerType->getAs<GenericTypeParamType>();
-              if (!genericParam)
-                return false;
-
-              auto genericParamDecl = genericParam->getOpaqueDecl();
-              if (!genericParamDecl)
-                return false;
-
-              param->diagnose(
-                 diag::opaque_type_in_parameter, true, interfaceType);
-              return true;
-            });
+    if (!isa<ClosureExpr>(owner)) {
+      Type interfaceType = param->getInterfaceType();
+      if (interfaceType->hasTypeParameter()) {
+        interfaceType.findIf([&](Type type) {
+          if (auto fnType = type->getAs<FunctionType>()) {
+            for (auto innerParam : fnType->getParams()) {
+              auto paramType = innerParam.getPlainType();
+              if (!paramType->hasTypeParameter())
+                continue;
+
+              bool hadError = paramType.findIf([&](Type innerType) {
+                auto genericParam = innerType->getAs<GenericTypeParamType>();
+                if (!genericParam)
+                  return false;
+
+                auto genericParamDecl = genericParam->getOpaqueDecl();
+                if (!genericParamDecl)
+                  return false;
+
+                param->diagnose(
+                   diag::opaque_type_in_parameter, true, interfaceType);
+                return true;
+              });
+
+              if (hadError)
+                return true;
+            }
 
-            if (hadError)
-              return true;
+            return false;
           }
 
           return false;
-        }
-
-        return false;
-      });
+        });
+      }
     }
 
     if (param->hasAttachedPropertyWrapper())
       (void) param->getPropertyWrapperInitializerInfo();
 
-    auto *SF = param->getDeclContext()->getParentSourceFile();
     if (!param->isInvalid()) {
+      auto *SF = owner->getParentSourceFile();
       param->visitAuxiliaryDecls([&](VarDecl *auxiliaryDecl) {
         if (!isa<ParamDecl>(auxiliaryDecl))
-          DeclChecker(param->getASTContext(), SF).visitBoundVariable(auxiliaryDecl);
+          DeclChecker(SF->getASTContext(), SF).visitBoundVariable(auxiliaryDecl);
       });
     }
 

test/type/opaque_parameters.swift

@@ -131,3 +131,18 @@ struct I61387_1 {
     }
   }
 }
+
+// However, it's fine if the inferred type of a closure refers to opaque parameters from the outer scope.
+public func combinator<T>(_: T, _: ((T) -> ()) -> ()) {}
+
+public func closureWithOpaqueParameterInConsumingPosition(p: some Any) {
+  // Single-expression
+  combinator(p) { $0(p) }
+
+  // Multi-expression
+  combinator(p) { fn in
+    let result: () = fn(p)
+    return result
+  }
+}
+