[QoI] improve diagnostics for contextual members with argument mismatch

Author: jtbandes

include/swift/AST/DiagnosticsSema.def

@@ -82,14 +82,18 @@ NOTE(any_as_anyobject_fixit, none,
      "cast 'Any' to 'AnyObject' or use 'as!' to force downcast to a more specific type to access members", ())
 
 ERROR(expected_argument_in_contextual_member,none,
-      "contextual member %0 expects argument of type %1", (DeclName, Type))
+      "member %0 expects argument of type %1", (DeclName, Type))
+ERROR(expected_parens_in_contextual_member,none,
+      "member %0 is a function; did you mean to call it?", (DeclName))
 
 ERROR(expected_result_in_contextual_member,none,
       "member %0 in %2 produces result of type %1, but context expects %2",
       (DeclName, Type, Type))
 
 ERROR(unexpected_argument_in_contextual_member,none,
-      "contextual member %0 has no associated value", (DeclName))
+      "member %0 takes no arguments", (DeclName))
+ERROR(unexpected_parens_in_contextual_member,none,
+      "member %0 is not a function", (DeclName))
 
 ERROR(could_not_use_value_member,none,
       "member %1 cannot be used on value of type %0", (Type, DeclName))

lib/Sema/CSDiag.cpp

@@ -6069,7 +6069,7 @@ bool FailureDiagnosis::visitUnresolvedMemberExpr(UnresolvedMemberExpr *E) {
     return true;
   }
 
-  auto argumentTy = candidateInfo[0].getArgumentType();
+  auto candidateArgTy = candidateInfo[0].getArgumentType();
 
   // Depending on how we matched, produce tailored diagnostics.
   switch (candidateInfo.closeness) {
@@ -6088,9 +6088,9 @@ bool FailureDiagnosis::visitUnresolvedMemberExpr(UnresolvedMemberExpr *E) {
   case CC_ExactMatch: {        // This is a perfect match for the arguments.
 
     // If we have an exact match, then we must have an argument list, check it.
-    if (argumentTy) {
+    if (candidateArgTy) {
       assert(E->getArgument() && "Exact match without argument?");
-      if (!typeCheckArgumentChildIndependently(E->getArgument(), argumentTy,
+      if (!typeCheckArgumentChildIndependently(E->getArgument(), candidateArgTy,
                                                candidateInfo))
         return true;
     }
@@ -6124,16 +6124,16 @@ bool FailureDiagnosis::visitUnresolvedMemberExpr(UnresolvedMemberExpr *E) {
 
   case CC_ArgumentLabelMismatch: { // Argument labels are not correct.
     auto argExpr = typeCheckArgumentChildIndependently(E->getArgument(),
-                                                       argumentTy,
+                                                       candidateArgTy,
                                                        candidateInfo);
     if (!argExpr) return true;
 
     // Construct the actual expected argument labels that our candidate
     // expected.
-    assert(argumentTy &&
+    assert(candidateArgTy &&
            "Candidate must expect an argument to have a label mismatch");
     SmallVector<Identifier, 2> argLabelsScratch;
-    auto arguments = decomposeArgType(argumentTy,
+    auto arguments = decomposeArgType(candidateArgTy,
                                       candidateInfo[0].getArgumentLabels(
                                         argLabelsScratch));
 
@@ -6151,26 +6151,40 @@ bool FailureDiagnosis::visitUnresolvedMemberExpr(UnresolvedMemberExpr *E) {
   case CC_ArgumentCountMismatch:  // This candidate has wrong # arguments.
     // If we have no argument, the candidates must have expected one.
     if (!E->getArgument()) {
-      if (!argumentTy)
+      if (!candidateArgTy)
         return false; // Candidate must be incorrect for some other reason.
 
       // Pick one of the arguments that are expected as an exemplar.
-      diagnose(E->getNameLoc(), diag::expected_argument_in_contextual_member,
-               E->getName(), argumentTy);
+      if (candidateArgTy->isVoid()) {
+        // If this member is () -> T, suggest adding parentheses.
+        diagnose(E->getNameLoc(), diag::expected_parens_in_contextual_member,
+                 E->getName())
+          .fixItInsertAfter(E->getEndLoc(), "()");
+      } else {
+        diagnose(E->getNameLoc(), diag::expected_argument_in_contextual_member,
+                 E->getName(), candidateArgTy);
+      }
       return true;
     }
 
-    // If an argument value was specified, but this is a simple enumerator, then
-    // we fail with a nice error message.
-    auto argTy = candidateInfo[0].getArgumentType();
-    if (!argTy) {
-      diagnose(E->getNameLoc(), diag::unexpected_argument_in_contextual_member,
-               E->getName());
+    // If an argument value was specified, but this member expects no arguments,
+    // then we fail with a nice error message.
+    if (!candidateArgTy) {
+      if (E->getArgument()->getType()->isVoid()) {
+        diagnose(E->getNameLoc(), diag::unexpected_parens_in_contextual_member,
+                 E->getName())
+          .fixItRemove(E->getArgument()->getSourceRange());
+      } else {
+        diagnose(E->getNameLoc(), diag::unexpected_argument_in_contextual_member,
+                 E->getName())
+          .highlight(E->getArgument()->getSourceRange());
+      }
       return true;
     }
 
-    assert(E->getArgument() && argTy && "Exact match without an argument?");
-    return !typeCheckArgumentChildIndependently(E->getArgument(), argTy,
+    assert(E->getArgument() && candidateArgTy &&
+           "Exact match without an argument?");
+    return !typeCheckArgumentChildIndependently(E->getArgument(), candidateArgTy,
                                                 candidateInfo);
   }
 

test/Constraints/diagnostics.swift

@@ -428,13 +428,13 @@ let _: [Color] = [1,2].map { _ in .Unknown("") }// expected-error {{missing argu
 
 let _: (Int) -> (Int, Color) = { ($0, .Unknown("")) } // expected-error {{missing argument label 'description:' in call}} {{48-48=description: }}
 let _: Color = .Unknown("") // expected-error {{missing argument label 'description:' in call}} {{25-25=description: }}
-let _: Color = .Unknown // expected-error {{contextual member 'Unknown' expects argument of type '(description: String)'}}
+let _: Color = .Unknown // expected-error {{member 'Unknown' expects argument of type '(description: String)'}}
 let _: Color = .Unknown(42) // expected-error {{cannot convert value of type 'Int' to expected argument type 'String'}}
 let _ : Color = .rainbow(42)  // expected-error {{argument passed to call that takes no arguments}}
 
 let _ : (Int, Float) = (42.0, 12)  // expected-error {{cannot convert value of type 'Double' to specified type 'Int'}}
 
-let _ : Color = .rainbow  // expected-error {{contextual member 'rainbow' expects argument of type '()'}}
+let _ : Color = .rainbow  // expected-error {{member 'rainbow' is a function; did you mean to call it?}} {{25-25=()}}
 
 let _: Color = .overload(a : 1.0)  // expected-error {{cannot convert value of type 'Double' to expected argument type 'Int'}}
 let _: Color = .overload(1.0)  // expected-error {{ambiguous reference to member 'overload'}}

test/Constraints/members.swift

@@ -575,7 +575,7 @@ enum SomeErrorType {
 
   static func someErrorFromString(_ str: String) -> SomeErrorType? {
     if str == "standalone" { return .StandaloneError }
-    if str == "underlying" { return .UnderlyingError }  // expected-error {{contextual member 'UnderlyingError' expects argument of type 'String'}}
+    if str == "underlying" { return .UnderlyingError }  // expected-error {{member 'UnderlyingError' expects argument of type 'String'}}
     return nil
   }
 }

test/decl/enum/enumtest.swift

@@ -219,8 +219,9 @@ func f() {
 }
 
 func union_error(_ a: ZeroOneTwoThree) {
-  var _ : ZeroOneTwoThree = .Zero(1) // expected-error {{contextual member 'Zero' has no associated value}}
-  var _ : ZeroOneTwoThree = .One // expected-error {{contextual member 'One' expects argument of type 'Int'}}
+  var _ : ZeroOneTwoThree = .Zero(1) // expected-error {{member 'Zero' takes no arguments}}
+  var _ : ZeroOneTwoThree = .Zero() // expected-error {{member 'Zero' is not a function}} {{34-36=}}
+  var _ : ZeroOneTwoThree = .One // expected-error {{member 'One' expects argument of type 'Int'}}
   var _ : ZeroOneTwoThree = .foo // expected-error {{type 'ZeroOneTwoThree' has no member 'foo'}}
   var _ : ZeroOneTwoThree = .foo() // expected-error {{type 'ZeroOneTwoThree' has no member 'foo'}}
 }