Sema: Undo changes in chronological order in SolverTrail::undo()

Author: slavapestov

lib/Sema/CSTrail.cpp

@@ -730,21 +730,10 @@ void SolverTrail::undo(unsigned toIndex) {
   ASSERT(!UndoActive);
   UndoActive = true;
 
-  // FIXME: Undo all changes in the correct order!
   for (unsigned i = Changes.size(); i > toIndex; i--) {
     auto change = Changes[i - 1];
-    if (change.Kind == ChangeKind::UpdatedTypeVariable) {
-      LLVM_DEBUG(llvm::dbgs() << "- "; change.dump(llvm::dbgs(), CS, 0));
-      change.undo(CS);
-    }
-  }
-
-  for (unsigned i = Changes.size(); i > toIndex; i--) {
-    auto change = Changes[i - 1];
-    if (change.Kind != ChangeKind::UpdatedTypeVariable) {
-      LLVM_DEBUG(llvm::dbgs() << "- "; change.dump(llvm::dbgs(), CS, 0));
-      change.undo(CS);
-    }
+    LLVM_DEBUG(llvm::dbgs() << "- "; change.dump(llvm::dbgs(), CS, 0));
+    change.undo(CS);
   }
 
   Changes.resize(toIndex);

test/Sema/issue-46000.swift

@@ -11,7 +11,7 @@ struct Data {}
 extension DispatchData {
   func asFoundationData<T>(execute: (Data) throws -> T) rethrows -> T {
     return try withUnsafeBytes { (ptr: UnsafePointer<Int8>) -> Void in
-      // expected-error@-1 {{cannot convert return expression of type 'Void' to return type 'T'}}
+      // expected-error@-1 {{declared closure result 'Void' is incompatible with contextual type 'T'}}
       let data = Data()
       return try execute(data) // expected-error {{cannot convert value of type 'T' to closure result type 'Void'}}
     }

test/type/opaque.swift

@@ -273,11 +273,8 @@ func associatedTypeIdentity() {
   sameType(cr, dr) // expected-error {{conflicting arguments to generic parameter 'T' ('(some R).S' (result type of 'candace') vs. '(some R).S' (result type of 'doug'))}}
   sameType(gary(candace()).r_out(), gary(candace()).r_out())
   sameType(gary(doug()).r_out(), gary(doug()).r_out())
-  // TODO(diagnostics): This is not great but the problem comes from the way solver discovers and attempts bindings, if we could detect that
-  // `(some R).S` from first reference to `gary()` in inconsistent with the second one based on the parent type of `S` it would be much easier to diagnose.
   sameType(gary(doug()).r_out(), gary(candace()).r_out())
-  // expected-error@-1:12 {{conflicting arguments to generic parameter 'T' ('some R' (result type of 'doug') vs. 'some R' (result type of 'candace'))}}
-  // expected-error@-2:34 {{conflicting arguments to generic parameter 'T' ('some R' (result type of 'doug') vs. 'some R' (result type of 'candace'))}}
+  // expected-error@-1:39 {{cannot convert value of type 'some R' (result of 'candace()') to expected argument type 'some R' (result of 'doug()')}}
 }
 
 func redeclaration() -> some P { return 0 } // expected-note 2{{previously declared}}