fix <rdar://problem/19259730> Using mutating methods in a struct initializer with a let property is rejected

while we're at it, improve the QoI for actually-invalid mutating method calls in struct initalizers.


Swift SVN r24030

include/swift/AST/DiagnosticsSIL.def

@@ -92,6 +92,10 @@ ERROR(variable_escape_before_initialized,sil_analysis,none,
 ERROR(self_use_before_init_in_delegatinginit,sil_analysis,none,
       "use of '%0' in delegating initializer before self.init is called",
       (StringRef))
+ERROR(self_use_before_init_in_structinit,sil_analysis,none,
+      "use of '%0' in delegating initializer before self.init is called",
+(StringRef))
+
 ERROR(variable_addrtaken_before_initialized,sil_analysis,none,
       "address of variable '%0' taken before it is initialized",
       (StringRef))

lib/SILPasses/DIMemoryUseCollector.cpp

@@ -662,10 +662,19 @@ void ElementUseCollector::collectUses(SILValue Pointer, unsigned BaseEltNo) {
         continue;
 
       // If this is an @inout parameter, it is like both a load and store.
-      case ParameterConvention::Indirect_Inout:
+      case ParameterConvention::Indirect_Inout: {
-        addElementUses(BaseEltNo, PointeeType, User, DIUseKind::InOutUse);
+        // If we're in the initializer for a struct, and this is a call to a
+        // mutating method, we model that as an escape of self.  If an
+        // individual sub-member is passed as inout, then we model that as an
+        // inout use.
+        auto Kind = DIUseKind::InOutUse;
+        if (TheMemory.isStructInitSelf() && Pointer == TheMemory.getAddress())
+          Kind = DIUseKind::Escape;
+          
+        addElementUses(BaseEltNo, PointeeType, User, Kind);
         continue;
       }
+      }
       llvm_unreachable("bad parameter convention");
     }
 

lib/SILPasses/DIMemoryUseCollector.h

@@ -106,6 +106,14 @@ public:
         return true;
     return false;
   }
+  
+  // True if the memory object is the 'self' argument of a struct initializer.
+  bool isStructInitSelf() const {
+    if (auto *MUI = dyn_cast<MarkUninitializedInst>(MemoryInst))
+      if (MUI->isRootSelf() && isa<StructDecl>(getType()->getAnyNominal()))
+        return true;
+    return false;
+  }
 
   // True if the memory object is the 'self' argument of a class initializer.
   bool isClassInitSelf() const {

lib/SILPasses/DefiniteInitialization.cpp

@@ -673,7 +673,13 @@ void LifetimeChecker::doIt() {
                        diag::return_from_init_without_self_init);
             break;
           }
-          
+        } else if (isa<ApplyInst>(Inst) && TheMemory.isStructInitSelf()) {
+          if (shouldEmitError(Inst)) {
+            diagnose(Module, Inst->getLoc(),
+                     diag::use_of_self_before_fully_init);
+            noteUninitializedMembers(Use);
+          }
+          break;
         } else if (isa<MarkFunctionEscapeInst>(Inst))
           DiagMessage = diag::global_variable_function_use_uninit;
         else if (isa<AddressToPointerInst>(Inst))

test/SILPasses/definite_init_diagnostics.swift

@@ -957,3 +957,32 @@ class r19254812Derived: r19254812Base{
     println(pi)  // ok, no diagnostic expected.
   }
 }
+
+
+// <rdar://problem/19259730> Using mutating methods in a struct initializer with a let property is rejected
+struct StructMutatingMethodTest {
+  let a, b: String  // expected-note 2 {{'self.b' not initialized}}
+  
+  init(x: String, y: String) {
+    a = x
+    b = y
+    mutate()   // ok
+  }
+  
+  init(x: String) {
+    a = x
+    mutate() // expected-error {{'self' used before all stored properties are initialized}}
+    b = x
+  }
+
+  init() {
+    a = ""
+    nonmutate() // expected-error {{'self' used before all stored properties are initialized}}
+    b = ""
+  }
+
+  mutating func mutate() {}
+  func nonmutate() {}
+}
+
+