Merge pull request #11765 from graydon/rdar-34111449-missing-case-in-SILOptimizer-dataflow-diagnostics

[SILOptimizer] Handle a missing case in DataflowDiagnostics.cpp

Author: graydon

lib/SILOptimizer/Mandatory/DataflowDiagnostics.cpp

@@ -43,6 +43,8 @@ static void diagnoseMissingReturn(const UnreachableInst *UI,
 
   if (auto *FD = FLoc.getAsASTNode<FuncDecl>()) {
     ResTy = FD->getResultInterfaceType();
+  } else if (auto *CD = FLoc.getAsASTNode<ConstructorDecl>()) {
+    ResTy = CD->getResultInterfaceType();
   } else if (auto *CE = FLoc.getAsASTNode<ClosureExpr>()) {
     ResTy = CE->getResultType();
   } else {

test/SILOptimizer/return.swift

@@ -94,6 +94,12 @@ func whileLoop(flag: Bool) -> Int {
   }
 } //expected-error {{missing return in a function expected to return 'Int'}}
 
+struct S {}
+extension S:ExpressibleByStringLiteral {
+  init!(stringLiteral:String) {
+  } // expected-error {{missing return in a function expected to return 'S!'}}
+}
+
 func whileTrueLoop() -> Int {
   var b = 1
   while (true) {