Merge pull request swiftlang#63109 from xedin/result-builder-if-else-sequences-5.8

[5.8][BuilderTransform] All `if` sequences without `else` should call `buildOptional`

Author: xedin

lib/Sema/BuilderTransform.cpp

@@ -1255,26 +1255,9 @@ class ResultBuilderTransform
         auto *builderCall =
             buildWrappedChainPayload(branchVarRef, i, numPayloads, isOptional);
 
-        auto isTopLevel = [&](Stmt *anchor) {
-          if (ifStmt->getThenStmt() == anchor)
-            return true;
-
-          // The situation is this:
-          //
-          // if <cond> {
-          //   ...
-          // } else if <other-cond> {
-          //   ...
-          // }
-          if (auto *innerIf = getAsStmt<IfStmt>(ifStmt->getElseStmt()))
-            return innerIf->getThenStmt() == anchor;
-
-          return ifStmt->getElseStmt() == anchor;
-        };
-
         // The operand should have optional type if we had optional results,
         // so we just need to call `buildIf` now, since we're at the top level.
-        if (isOptional && isTopLevel(anchor)) {
+        if (isOptional) {
           builderCall = buildCallIfWanted(ifStmt->getThenStmt()->getStartLoc(),
                                           builder.getBuildOptionalId(),
                                           builderCall, /*argLabels=*/{});

test/Constraints/result_builder.swift

@@ -1252,3 +1252,134 @@ do {
   }
   // CHECK: the answer
 }
+
+protocol TestIfSequences {
+}
+
+struct A: TestIfSequences {}
+struct B: TestIfSequences {}
+struct C: TestIfSequences {}
+struct D: TestIfSequences {}
+
+func testOptionalIfElseSequences() {
+  func check<T>(_ v: TestIfSequences,
+                @TupleBuilder body: (TestIfSequences) throws -> T) rethrows {
+    print(try body(v))
+  }
+
+  check(A()) { v in
+    if let a = v as? A {
+      a
+    } else if let b = v as? B {
+      b
+    } else if let c = v as? C {
+      c
+    }
+  }
+
+  check(B()) { v in
+    if let a = v as? A {
+      a
+    } else if let b = v as? B {
+      b
+    } else if let c = v as? C {
+      c
+    }
+  }
+
+  check(C()) { v in
+    if let a = v as? A {
+      a
+    } else if let b = v as? B {
+      b
+    } else if let c = v as? C {
+      c
+    }
+  }
+
+  check(D()) { v in
+    if let a = v as? A {
+      a
+    } else if let b = v as? B {
+      b
+    } else if let c = v as? C {
+      c
+    } else {
+      D()
+    }
+  }
+
+  check(A()) { v in
+    if let a = v as? A {
+      a
+    } else {
+      if let b = v as? B {
+        b
+      }
+
+      if let c = v as? C {
+        c
+      } else if let d = v as? D {
+        d
+      }
+    }
+  }
+
+  check(B()) { v in
+    if let a = v as? A {
+      a
+    } else {
+      if let b = v as? B {
+        b
+      }
+
+      if let c = v as? C {
+        c
+      } else if let d = v as? D {
+        d
+      }
+    }
+  }
+
+  check(C()) { v in
+    if let a = v as? A {
+      a
+    } else {
+      if let b = v as? B {
+        b
+      }
+
+      if let c = v as? C {
+        c
+      } else if let d = v as? D {
+        d
+      }
+    }
+  }
+
+  check(D()) { v in
+    if let a = v as? A {
+      a
+    } else {
+      if let b = v as? B {
+        b
+      }
+
+      if let c = v as? C {
+        c
+      } else if let d = v as? D {
+        d
+      }
+    }
+  }
+}
+
+testOptionalIfElseSequences()
+// CHECK: Optional(main.Either<main.Either<main.A, main.B>, main.C>.first(main.Either<main.A, main.B>.first(main.A())))
+// CHECK-NEXT: Optional(main.Either<main.Either<main.A, main.B>, main.C>.first(main.Either<main.A, main.B>.second(main.B())))
+// CHECK-NEXT: Optional(main.Either<main.Either<main.A, main.B>, main.C>.second(main.C()))
+// CHECK-NEXT: second(main.Either<main.C, main.D>.second(main.D()))
+// CHECK-NEXT: first(main.A())
+// CHECK-NEXT: second(Optional(main.B()), nil)
+// CHECK-NEXT: second(nil, Optional(main.Either<main.C, main.D>.first(main.C())))
+// CHECK-NEXT: second(nil, Optional(main.Either<main.C, main.D>.second(main.D())))