[Diagnostics] Add notes for the type_cannot_conform error that point

hborla · hborla · commit 2a7e0099d24a · 2019-09-17T09:22:07.000-07:00
to the declaration that requires protocol conformance.
diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
@@ -1664,6 +1664,15 @@ ERROR(type_cannot_conform, none,
       "%select{|protocol }0type %1 cannot conform to %2; "
       "only struct/enum/class types can conform to protocols",
       (bool, Type, Type))
+NOTE(required_by_opaque_return,none,
+    "required by opaque return type of %0 %1", (DescriptiveDeclKind, DeclName))
+NOTE(required_by_decl,none,
+     "required by %0 %1 where %2 = %3",
+     (DescriptiveDeclKind, DeclName, Type, Type))
+NOTE(required_by_decl_ref,none,
+     "required by referencing %0 %1 on %2 where %3 = %4",
+     (DescriptiveDeclKind, DeclName, Type, Type, Type))
+
 ERROR(protocol_does_not_conform_static,none,
       "%0 cannot be used as a type conforming to protocol %1 because %1 "
       "has static requirements",
diff --git a/lib/Sema/CSDiagnostics.cpp b/lib/Sema/CSDiagnostics.cpp
@@ -597,17 +597,54 @@ bool MissingConformanceFailure::diagnoseAsError() {
 
 bool MissingConformanceFailure::diagnoseTypeCannotConform(Expr *anchor,
     Type nonConformingType, Type protocolType) const {
-  if (nonConformingType->is<AnyFunctionType>() ||
+  if (!(nonConformingType->is<AnyFunctionType>() ||
       nonConformingType->is<TupleType>() ||
       nonConformingType->isExistentialType() ||
-      nonConformingType->is<AnyMetatypeType>()) {
-    emitDiagnostic(anchor->getLoc(), diag::type_cannot_conform,
-                   nonConformingType->isExistentialType(), nonConformingType,
-                   protocolType);
+      nonConformingType->is<AnyMetatypeType>())) {
+    return false;
+  }
+
+  emitDiagnostic(anchor->getLoc(), diag::type_cannot_conform,
+                 nonConformingType->isExistentialType(), nonConformingType,
+                 protocolType);
+
+  if (auto *OTD = dyn_cast<OpaqueTypeDecl>(AffectedDecl)) {
+    auto *namingDecl = OTD->getNamingDecl();
+    if (auto *repr = namingDecl->getOpaqueResultTypeRepr()) {
+      emitDiagnostic(repr->getLoc(), diag::required_by_opaque_return,
+                     namingDecl->getDescriptiveKind(), namingDecl->getFullName())
+          .highlight(repr->getSourceRange());
+    }
     return true;
   }
 
-  return false;
+  auto &req = getRequirement();
+  auto *reqDC = getRequirementDC();
+  auto *genericCtx = getGenericContext();
+  auto noteLocation = reqDC->getAsDecl()->getLoc();
+
+  if (!noteLocation.isValid())
+    noteLocation = anchor->getLoc();
+
+  if (isConditional()) {
+    emitDiagnostic(noteLocation, diag::requirement_implied_by_conditional_conformance,
+                   resolveType(Conformance->getType()),
+                   Conformance->getProtocol()->getDeclaredInterfaceType());
+  } else if (genericCtx != reqDC && (genericCtx->isChildContextOf(reqDC) ||
+                                     isStaticOrInstanceMember(AffectedDecl))) {
+    emitDiagnostic(noteLocation, diag::required_by_decl_ref,
+                   AffectedDecl->getDescriptiveKind(),
+                   AffectedDecl->getFullName(),
+                   reqDC->getSelfNominalTypeDecl()->getDeclaredType(),
+                   req.getFirstType(), nonConformingType);
+  } else {
+    emitDiagnostic(noteLocation, diag::required_by_decl,
+                   AffectedDecl->getDescriptiveKind(),
+                   AffectedDecl->getFullName(), req.getFirstType(),
+                   nonConformingType);
+  }
+
+  return true;
 }
 
 Optional<Diag<Type, Type>> GenericArgumentsMismatchFailure::getDiagnosticFor(
diff --git a/lib/Sema/CSDiagnostics.h b/lib/Sema/CSDiagnostics.h
@@ -308,6 +308,10 @@ class RequirementFailure : public FailureDiagnostic {
            isa<BinaryExpr>(apply);
   }
 
+  /// Determine whether given declaration represents a static
+  /// or instance property/method, excluding operators.
+  static bool isStaticOrInstanceMember(const ValueDecl *decl);
+
 private:
   /// Retrieve declaration associated with failing generic requirement.
   ValueDecl *getDeclRef() const;
@@ -317,10 +321,6 @@ class RequirementFailure : public FailureDiagnostic {
 
   void emitRequirementNote(const Decl *anchor, Type lhs, Type rhs) const;
 
-  /// Determine whether given declaration represents a static
-  /// or instance property/method, excluding operators.
-  static bool isStaticOrInstanceMember(const ValueDecl *decl);
-
   /// If this is a failure in conditional requirement, retrieve
   /// conformance information.
   ProtocolConformance *
diff --git a/test/Constraints/diagnostics.swift b/test/Constraints/diagnostics.swift
@@ -28,6 +28,9 @@ func f3(_: @escaping (_: @escaping (Int) -> Float) -> Int) {}
 func f4(_ x: Int) -> Int { }
 
 func f5<T : P2>(_ : T) { }
+// expected-note@-1 {{required by global function 'f5' where 'T' = '(Int) -> Int'}}
+// expected-note@-2 {{required by global function 'f5' where 'T' = '(Int, String)'}}
+// expected-note@-3 {{required by global function 'f5' where 'T' = 'Int.Type'}}
 
 func f6<T : P, U : P>(_ t: T, _ u: U) where T.SomeType == U.SomeType {}
 
@@ -96,6 +99,7 @@ func f7() -> (c: Int, v: A) {
 }
 
 func f8<T:P2>(_ n: T, _ f: @escaping (T) -> T) {}
+// expected-note@-1 {{required by global function 'f8' where 'T' = 'Tup' (aka '(Int, Double)')}}
 f8(3, f4) // expected-error {{argument type 'Int' does not conform to expected type 'P2'}}
 typealias Tup = (Int, Double)
 func f9(_ x: Tup) -> Tup { return x }
diff --git a/test/Constraints/function_builder_diags.swift b/test/Constraints/function_builder_diags.swift
@@ -144,7 +144,7 @@ struct TupleP<U> : P {
 
 @_functionBuilder
 struct Builder {
-  static func buildBlock<S0, S1>(_ stmt1: S0, _ stmt2: S1)
+  static func buildBlock<S0, S1>(_ stmt1: S0, _ stmt2: S1) // expected-note {{required by static method 'buildBlock' where 'S1' = 'Label<Any>.Type'}}
            -> TupleP<(S0, S1)> where S0: P, S1: P {
     return TupleP((stmt1, stmt2))
   }
diff --git a/test/Constraints/generics.swift b/test/Constraints/generics.swift
@@ -192,6 +192,7 @@ func r22459135() {
 // <rdar://problem/19710848> QoI: Friendlier error message for "[] as Set"
 // <rdar://problem/22326930> QoI: "argument for generic parameter 'Element' could not be inferred" lacks context
 _ = [] as Set  // expected-error {{protocol type 'Any' cannot conform to 'Hashable'; only struct/enum/class types can conform to protocols}}
+// expected-note@-1 {{required by generic struct 'Set' where 'Element' = 'Any'}}
 
 
 //<rdar://problem/22509125> QoI: Error when unable to infer generic archetype lacks greatness
diff --git a/test/Constraints/operator.swift b/test/Constraints/operator.swift
@@ -221,6 +221,7 @@ func rdar46459603() {
   // expected-note@-2  {{expected an argument list of type '(Self, Self)'}}
   _ = [arr.values] == [[e]]
   // expected-error@-1 {{protocol type 'Any' cannot conform to 'Equatable'; only struct/enum/class types can conform to protocols}}
+  // expected-note@-2 {{requirement from conditional conformance of '[Any]' to 'Equatable'}}
 }
 
 // SR-10843
diff --git a/test/Generics/conditional_conformances_literals.swift b/test/Generics/conditional_conformances_literals.swift
@@ -16,6 +16,7 @@ extension Array: Conforms where Element: Conforms {}
 // expected-note@-1 5 {{requirement from conditional conformance of '[Fails]' to 'Conforms'}}
 extension Dictionary: Conforms where Value: Conforms {}
 // expected-note@-1 3 {{requirement from conditional conformance of '[Int : Fails]' to 'Conforms'}}
+// expected-note@-2 2 {{requirement from conditional conformance of '[Int : Conforms]' to 'Conforms'}}
 
 let works = Works()
 let fails = Fails()
diff --git a/test/Generics/existential_restrictions.swift b/test/Generics/existential_restrictions.swift
@@ -9,7 +9,10 @@ protocol CP : class { }
 }
 
 func fP<T : P>(_ t: T) { }
+// expected-note@-1 {{required by global function 'fP' where 'T' = 'P'}}
+// expected-note@-2 {{required by global function 'fP' where 'T' = 'OP & P'}}
 func fOP<T : OP>(_ t: T) { }
+// expected-note@-1 {{required by global function 'fOP' where 'T' = 'OP & P'}}
 func fOPE(_ t: OP) { }
 func fSP<T : SP>(_ t: T) { }
 func fAO<T : AnyObject>(_ t: T) { }
@@ -73,6 +76,7 @@ protocol Mine {}
 class M1: Mine {}
 class M2: Mine {}
 extension Collection where Iterator.Element : Mine {
+// expected-note@-1 {{required by referencing instance method 'takeAll()' on 'Collection'}}
     func takeAll() {}
 }
 
diff --git a/test/decl/protocol/conforms/error_self_conformance.swift b/test/decl/protocol/conforms/error_self_conformance.swift
@@ -1,6 +1,9 @@
 // RUN: %target-typecheck-verify-swift
 
 func wantsError<T: Error>(_: T) {}
+// expected-note@-1 {{required by global function 'wantsError' where 'T' = 'ErrorRefinement'}}
+// expected-note@-2 {{required by global function 'wantsError' where 'T' = 'Error & OtherProtocol'}}
+// expected-note@-3 {{required by global function 'wantsError' where 'T' = 'C & Error'}}
 
 func testSimple(error: Error) {
   wantsError(error)
diff --git a/test/type/opaque.swift b/test/type/opaque.swift
@@ -376,8 +376,9 @@ protocol P_51641323 {
 
 func rdar_51641323() {
   struct Foo: P_51641323 {
-    var foo: some P_51641323 { {} }
-    // expected-error@-1 {{type '() -> ()' cannot conform to 'P_51641323'; only struct/enum/class types can conform to protocols}}
+    var foo: some P_51641323 { // expected-note {{required by opaque return type of property 'foo'}}
+      {} // expected-error {{type '() -> ()' cannot conform to 'P_51641323'; only struct/enum/class types can conform to protocols}}
+    }
   }
 }
 
diff --git a/test/type/subclass_composition.swift b/test/type/subclass_composition.swift
@@ -300,6 +300,7 @@ func dependentMemberTypes<T : BaseIntAndP2>(
 
 func conformsToAnyObject<T : AnyObject>(_: T) {}
 func conformsToP1<T : P1>(_: T) {}
+// expected-note@-1 {{required by global function 'conformsToP1' where 'T' = 'P1'}}
 func conformsToP2<T : P2>(_: T) {}
 func conformsToBaseIntAndP2<T : Base<Int> & P2>(_: T) {}
 // expected-note@-1 {{where 'T' = 'FakeDerived'}}
diff --git a/validation-test/Sema/type_checker_crashers_fixed/rdar27830834.swift b/validation-test/Sema/type_checker_crashers_fixed/rdar27830834.swift
@@ -1,4 +1,6 @@
 // RUN: %target-swift-frontend %s -typecheck -verify
 
 var d = [String:String]()
-_ = "\(d.map{ [$0 : $0] })" // expected-error {{type '(key: String, value: String)' cannot conform to 'Hashable'; only struct/enum/class types can conform to protocols}}
+_ = "\(d.map{ [$0 : $0] })"
+// expected-error@-1 {{type '(key: String, value: String)' cannot conform to 'Hashable'; only struct/enum/class types can conform to protocols}}
+// expected-note@-2 {{required by generic struct 'Dictionary' where 'Key' = '(key: String, value: String)'}}
diff --git a/validation-test/compiler_crashers_2_fixed/0196-rdar48937223.swift b/validation-test/compiler_crashers_2_fixed/0196-rdar48937223.swift
@@ -3,6 +3,7 @@
 protocol P {}
 
 func fn<T, U: P>(_ arg1: T, arg2: (T) -> U) {}
+// expected-note@-1 {{required by global function 'fn(_:arg2:)' where 'U' = '()'}}
 
 func test(str: String) {
   fn(str) { arg in // expected-error {{type '()' cannot conform to 'P'; only struct/enum/class types can conform to protocols}}
diff --git a/validation-test/compiler_crashers_fixed/00017-llvm-foldingset-llvm-attributesetnode-nodeequals.swift b/validation-test/compiler_crashers_fixed/00017-llvm-foldingset-llvm-attributesetnode-nodeequals.swift
@@ -17,6 +17,7 @@ protocol BooleanProtocol {
 extension Bool : BooleanProtocol {
   var boolValue: Bool { return self }
 }
-func f<T : BooleanProtocol>(_ b: T) {
-}
+func f<T : BooleanProtocol>(_ b: T) {}
+// expected-note@-1 {{required by global function 'f' where 'T' = 'BooleanProtocol'}}
+
 f(true as BooleanProtocol) // expected-error {{protocol type 'BooleanProtocol' cannot conform to 'BooleanProtocol'; only struct/enum/class types can conform to protocols}}

Original file line number	Diff line number	Diff line change
`@@ -144,7 +144,7 @@ struct TupleP<U> : P {`
`144`	`144`
`145`	`145`	`@_functionBuilder`
`146`	`146`	`struct Builder {`
`147`		`- static func buildBlock<S0, S1>(_ stmt1: S0, _ stmt2: S1)`
	`147`	`+ static func buildBlock<S0, S1>(_ stmt1: S0, _ stmt2: S1) // expected-note {{required by static method 'buildBlock' where 'S1' = 'Label<Any>.Type'}}`
`148`	`148`	`-> TupleP<(S0, S1)> where S0: P, S1: P {`
`149`	`149`	`return TupleP((stmt1, stmt2))`
`150`	`150`	`}`
Original file line number	Diff line number	Diff line change
`@@ -221,6 +221,7 @@ func rdar46459603() {`
`221`	`221`	`// expected-note@-2 {{expected an argument list of type '(Self, Self)'}}`
`222`	`222`	`_ = [arr.values] == [[e]]`
`223`	`223`	`// expected-error@-1 {{protocol type 'Any' cannot conform to 'Equatable'; only struct/enum/class types can conform to protocols}}`
	`224`	`+ // expected-note@-2 {{requirement from conditional conformance of '[Any]' to 'Equatable'}}`
`224`	`225`	`}`
`225`	`226`
`226`	`227`	`// SR-10843`