Fix bug: wrong var used (#62683)

* Fix bug: wrong var used

* Augment tests for cases returning from initializers without initializing all stored properties

Author: valeriyvan

lib/SILOptimizer/Mandatory/DataflowDiagnostics.cpp

@@ -50,7 +50,7 @@ static void diagnoseMissingReturn(const UnreachableInst *UI,
     BS = FD->getBody(/*canSynthesize=*/false);
   } else if (auto *CD = FLoc.getAsASTNode<ConstructorDecl>()) {
     ResTy = CD->getResultInterfaceType();
-    BS = FD->getBody();
+    BS = CD->getBody();
   } else if (auto *CE = FLoc.getAsASTNode<ClosureExpr>()) {
     ResTy = CE->getResultType();
     BS = CE->getBody();

test/SILOptimizer/return.swift

@@ -220,7 +220,14 @@ func f_56150() {
 // https://github.com/apple/swift/issues/56857
 
 struct S_56857 {
-    let b = true
+    init(_ i: Int) {
+        if i > 0 {
+            b = false
+        }
+    } // expected-error {{return from initializer without initializing all stored properties}}
+
+    let b: Bool // expected-note {{'self.b' not initialized}}
+
     var x: Int {
         if b {
             return 0
@@ -238,8 +245,14 @@ struct S_56857 {
 }
 
 class C_56857 {
+  init(_ i: Int) {
+    if i > 0 {
+      b = false
+    }
+  } // expected-error {{return from initializer without initializing all stored properties}}
+
   static let a = false
-  let b = true
+  let b: Bool // expected-note {{'self.b' not initialized}}
 
   func method() -> Int {
     if b {