Merge pull request #38777 from guitard0g/unreachable-keypath

[diagnose-unreachable] Fix incorrect diagnostic on keypath creation

Author: Josh Learn

lib/SILGen/SILGenExpr.cpp

@@ -2692,7 +2692,6 @@ getRepresentativeAccessorForKeyPath(AbstractStorageDecl *storage) {
 }
 
 static SILFunction *getOrCreateKeyPathGetter(SILGenModule &SGM,
-                         SILLocation loc,
                          AbstractStorageDecl *property,
                          SubstitutionMap subs,
                          GenericEnvironment *genericEnv,
@@ -2759,6 +2758,8 @@ static SILFunction *getOrCreateKeyPathGetter(SILGenModule &SGM,
   auto name = Mangle::ASTMangler()
     .mangleKeyPathGetterThunkHelper(property, genericSig, baseType,
                                     subs, expansion);
+  auto loc = RegularLocation::getAutoGeneratedLocation();
+
   SILGenFunctionBuilder builder(SGM);
   auto thunk = builder.getOrCreateSharedFunction(
       loc, name, signature, IsBare, IsNotTransparent,
@@ -2806,7 +2807,6 @@ static SILFunction *getOrCreateKeyPathGetter(SILGenModule &SGM,
   auto baseSubstValue = emitKeyPathRValueBase(subSGF, property,
                                                loc, baseArg,
                                                baseType, subs);
-  
   auto subscriptIndices =
     loadIndexValuesForKeyPathComponent(subSGF, loc, property,
                                        indexes, indexPtrArg);
@@ -2832,7 +2832,6 @@ static SILFunction *getOrCreateKeyPathGetter(SILGenModule &SGM,
 }
 
 static SILFunction *getOrCreateKeyPathSetter(SILGenModule &SGM,
-                          SILLocation loc,
                           AbstractStorageDecl *property,
                           SubstitutionMap subs,
                           GenericEnvironment *genericEnv,
@@ -2907,6 +2906,7 @@ static SILFunction *getOrCreateKeyPathSetter(SILGenModule &SGM,
   auto name = Mangle::ASTMangler()
     .mangleKeyPathSetterThunkHelper(property, genericSig, baseType,
                                     subs, expansion);
+  auto loc = RegularLocation::getAutoGeneratedLocation();
 
   SILGenFunctionBuilder builder(SGM);
   auto thunk = builder.getOrCreateSharedFunction(
@@ -3536,13 +3536,13 @@ SILGenModule::emitKeyPathComponentForDecl(SILLocation loc,
     // expected by the key path runtime.
     auto id = getIdForKeyPathComponentComputedProperty(*this, var,
                                                        strategy);
-    auto getter = getOrCreateKeyPathGetter(*this, loc,
+    auto getter = getOrCreateKeyPathGetter(*this,
              var, subs,
              needsGenericContext ? genericEnv : nullptr,
              expansion, {}, baseTy, componentTy);
 
     if (isSettableInComponent()) {
-      auto setter = getOrCreateKeyPathSetter(*this, loc,
+      auto setter = getOrCreateKeyPathSetter(*this,
              var, subs,
              needsGenericContext ? genericEnv : nullptr,
              expansion, {}, baseTy, componentTy);
@@ -3587,7 +3587,7 @@ SILGenModule::emitKeyPathComponentForDecl(SILLocation loc,
     }
 
     auto id = getIdForKeyPathComponentComputedProperty(*this, decl, strategy);
-    auto getter = getOrCreateKeyPathGetter(*this, loc,
+    auto getter = getOrCreateKeyPathGetter(*this,
              decl, subs,
              needsGenericContext ? genericEnv : nullptr,
              expansion,
@@ -3596,7 +3596,7 @@ SILGenModule::emitKeyPathComponentForDecl(SILLocation loc,
 
     auto indexPatternsCopy = getASTContext().AllocateCopy(indexPatterns);
     if (isSettableInComponent()) {
-      auto setter = getOrCreateKeyPathSetter(*this, loc,
+      auto setter = getOrCreateKeyPathSetter(*this,
              decl, subs,
              needsGenericContext ? genericEnv : nullptr,
              expansion,

test/SILGen/sil_locations.swift

@@ -417,3 +417,29 @@ func testWhile() {
 
 
 }
+
+// Check that the sil location of keypath getter/setter functions is
+// marked as autogenerated.
+struct Struct {
+  var structProperty: InnerStruct {
+    get { InnerStruct() }
+    set(newStruct) { }
+  }
+
+  struct InnerStruct {}
+}
+
+func testKeyPathGetterSetterAutogen() -> Struct.InnerStruct {
+  let kp = \Struct.structProperty
+  var s = Struct()
+  let innerS = Struct.InnerStruct()
+
+  s[keyPath: kp] = innerS
+  return s[keyPath: kp]
+  // Autogenerated keypath getter
+  // CHECK-LABEL: sil shared [thunk] [ossa] @$s13sil_locations6StructV14structProperty{{[_0-9a-zA-Z]*}}TK
+  // CHECK: load {{.*}} loc "<compiler-generated>":0:0{{.*}}<invalid loc>:auto_gen
+  // Autogenerated keypath setter
+  // CHECK-LABEL: sil shared [thunk] [ossa] @$s13sil_locations6StructV14structProperty{{[_0-9a-zA-Z]*}}Tk
+  // CHECK: load {{.*}} loc "<compiler-generated>":0:0{{.*}}<invalid loc>:auto_gen
+}

test/SILOptimizer/diagnose_unreachable.swift

@@ -470,3 +470,48 @@ extension Collection {
   }
 }
 
+// rdar://80415811
+// Incorrect unreachable code diagnostic for keypath to empty Enum caused by
+// the generated keypath getter function having an uninhabited return type.
+// The getter function was previously tied to the source location of the
+// corresponding keypath expression, which caused it to be diagnosed as
+// user code. The getter and setter functions now have an autogenerated
+// source location so we should not expect an unreachable code warning until
+// the keypath expression is actually used.
+struct StructWithNeverProp {
+  var property: Never {
+    fatalError()
+  }
+}
+
+func keypathToEmptyEnum() -> Never {
+  // Check that the generated keypath getter function for this property
+  // does not trigger an unreachable code warning here.
+  let kp = \StructWithNeverProp.property // no warning
+  let s = StructWithNeverProp()
+  // Emit a diagnostic here becase the keypath is actually used.
+  let prop = s[keyPath: kp]
+    // expected-warning@-1 {{will never be executed}} \
+    // expected-note {{a call to a never-returning function}} \
+    // expected-warning {{constant 'prop' inferred to have type 'Never', which is an enum with no cases}} \
+    // expected-note {{add an explicit type annotation to silence this warning}}
+  return prop
+}
+
+struct OuterStruct {
+  public let innerEnum: InnerEnum
+  public enum InnerEnum { }
+}
+
+@dynamicMemberLookup
+public enum DynamicLookupEnum {
+    subscript<T>(dynamicMember keyPath: KeyPath<OuterStruct, T>) -> T {
+        fatalError()
+    }
+}
+
+func keypathWithDynamicLookup() {
+  // Check that we still don't diagnose the keypath getter as unreachable
+  // when used in conjuction with a dynamicMemberLookup enum.
+  let _ = \DynamicLookupEnum.innerEnum // no warning
+}