[typechecker] allow non-optional enum case match with optional enum

Author: Suyash Srijan

lib/Sema/TypeCheckPattern.cpp

@@ -1395,19 +1395,24 @@ bool TypeChecker::coercePatternToType(Pattern *&P, TypeResolution resolution,
             goto recur;
           }
 
-          auto diag = diagnose(EEP->getLoc(),
-                               diag::enum_element_pattern_member_not_found,
-                               EEP->getName().str(), type);
-
           // If we have an optional type let's try to see if the case
-          // exists in its base type, if so we can suggest a fix-it for that.
+          // exists in its base type and create a new pattern which contains
+          // the enum case.
           if (auto baseType = type->getOptionalObjectType()) {
             if (lookupEnumMemberElement(*this, dc, baseType, EEP->getName(),
-                                        EEP->getLoc()))
-              diag.fixItInsertAfter(EEP->getEndLoc(), "?");
+                                        EEP->getLoc())) {
+              P = new (Context)
+                  OptionalSomePattern(EEP, EEP->getEndLoc(), true);
+              P->setImplicit();
+              return coercePatternToType(P, resolution, type, options);
+            } else {
+              diagnose(EEP->getLoc(),
+                       diag::enum_element_pattern_member_not_found,
+                       EEP->getName().str(), type);
+              return true;
+            }
           }
         }
-        return true;
       }
       enumTy = type;
     } else {

test/Constraints/patterns.swift

@@ -254,7 +254,7 @@ enum SR2057 {
 }
 
 let sr2057: SR2057?
-if case .foo = sr2057 { } // expected-error{{enum case 'foo' not found in type 'SR2057?'}}
+if case .foo = sr2057 { } // Ok
 
 
 // Invalid 'is' pattern
@@ -333,10 +333,10 @@ struct S_32241441 {
 func rdar32241441() {
   let s: S_32241441? = S_32241441()
 
-  switch s?.type {
-  case .foo: // expected-error {{enum case 'foo' not found in type 'S_32241441.E_32241441?'}} {{12-12=?}}
+  switch s?.type { // expected-error {{switch must be exhaustive}} expected-note {{add missing case: '.none'}}
+  case .foo: // Ok
     break;
-  case .bar: // expected-error {{enum case 'bar' not found in type 'S_32241441.E_32241441?'}} {{12-12=?}}
+  case .bar: // Ok
     break;
   }
 }
@@ -409,4 +409,15 @@ func test8347() -> String {
   }
 }
 
+enum SR_7799 {
+ case baz
+ case bar
+}
+
+let sr7799: SR_7799? = .bar
 
+switch sr7799 {
+ case .bar?: break // Ok
+ case .baz: break // Ok
+ default: break
+}