[CSDiagnostics] Split no exact match diagnostic into three choices

1. If this is a special name avoid printing it because
   printing kind is sufficient;

2. If all of the labels match, print a full name;

3. If labels in different choices are different, it means
   that we can only print a base name.

Author: xedin

include/swift/AST/DiagnosticsSema.def

@@ -57,6 +57,9 @@ ERROR(ambiguous_member_overload_set,none,
 ERROR(ambiguous_reference_to_decl,none,
       "ambiguous reference to %0 %1", (DescriptiveDeclKind, DeclName))
 ERROR(no_overloads_match_exactly_in_call,none,
+      "no exact matches in call to %0 %1",
+      (DescriptiveDeclKind, DeclName))
+ERROR(no_overloads_match_exactly_in_call_no_labels,none,
       "no exact matches in call to %0 %1",
       (DescriptiveDeclKind, DeclBaseName))
 ERROR(no_overloads_match_exactly_in_call_special,none,

lib/Sema/ConstraintSystem.cpp

@@ -2490,15 +2490,28 @@ bool ConstraintSystem::diagnoseAmbiguityWithFixes(
                   diag::could_not_find_subscript_member_did_you_mean,
                   getType(UDE->getBase()));
     } else {
-      auto name = decl->getBaseName();
+      auto name = decl->getFullName();
+      // Three choices here:
+      // 1. If this is a special name avoid printing it because
+      //    printing kind is sufficient;
+      // 2. If all of the labels match, print a full name;
+      // 3. If labels in different choices are different, it means
+      //    that we can only print a base name.
       if (name.isSpecial()) {
         TC.diagnose(commonAnchor->getLoc(),
                     diag::no_overloads_match_exactly_in_call_special,
                     decl->getDescriptiveKind());
-      } else {
+      } else if (llvm::all_of(distinctChoices,
+                              [&name](const ValueDecl *choice) {
+                                return choice->getFullName() == name;
+                              })) {
         TC.diagnose(commonAnchor->getLoc(),
                     diag::no_overloads_match_exactly_in_call,
                     decl->getDescriptiveKind(), name);
+      } else {
+        TC.diagnose(commonAnchor->getLoc(),
+                    diag::no_overloads_match_exactly_in_call_no_labels,
+                    decl->getDescriptiveKind(), name.getBaseName());
       }
     }
 

test/decl/ext/protocol.swift

@@ -236,9 +236,9 @@ extension P4 where Self.AssocP4 == Bool {
 }
 
 func testP4(_ s4a: S4a, s4b: S4b, s4c: S4c, s4d: S4d) {
-  s4a.extP4a() // expected-error{{no exact matches in call to instance method 'extP4a'}}
+  s4a.extP4a() // expected-error{{no exact matches in call to instance method 'extP4a()'}}
   s4b.extP4a() // ok
-  s4c.extP4a() // expected-error{{no exact matches in call to instance method 'extP4a'}}
+  s4c.extP4a() // expected-error{{no exact matches in call to instance method 'extP4a()'}}
   s4c.extP4Int() // okay
   var b1 = s4d.extP4a() // okay, "Bool" version
   b1 = true // checks type above