[typechecker] check for typealias as well

Author: Suyash Srijan

include/swift/AST/Decl.h

@@ -219,6 +219,9 @@ struct OverloadSignature {
   /// Whether this is a nominal type.
   unsigned IsNominal : 1;
 
+  /// Whether this is a type alias.
+  unsigned IsTypeAlias : 1;
+
   /// Whether this signature is part of a protocol extension.
   unsigned InProtocolExtension : 1;
 

lib/AST/Decl.cpp

@@ -2104,6 +2104,12 @@ bool swift::conflicting(ASTContext &ctx,
     return true;
   }
 
+  // Typealiases and enum elements always conflict with each other.
+  if ((sig1.IsTypeAlias && sig2.IsEnumElement) ||
+      (sig1.IsEnumElement && sig2.IsTypeAlias)) {
+    return true;
+  }
+
   // Enum elements always conflict with each other. At this point, they
   // have the same base name but different types.
   if (sig1.IsEnumElement && sig2.IsEnumElement) {
@@ -2270,6 +2276,7 @@ OverloadSignature ValueDecl::getOverloadSignature() const {
   signature.IsFunction = isa<AbstractFunctionDecl>(this);
   signature.IsEnumElement = isa<EnumElementDecl>(this);
   signature.IsNominal = isa<NominalTypeDecl>(this);
+  signature.IsTypeAlias = isa<TypeAliasDecl>(this);
 
   // Unary operators also include prefix/postfix.
   if (auto func = dyn_cast<FuncDecl>(this)) {

test/decl/overload.swift

@@ -568,10 +568,30 @@ enum SR_10084_E_10 {
 
 enum SR_10084_E_11 {
   case A // expected-note {{found this candidate}} // expected-note {{'A' previously declared here}}
-  static let A: SR_10084_E_11 = .A // expected-note {{found this candidate}} // expected-error {{invalid redeclaration of 'A'}} // expected-error {{ambiguous use of 'A'}}
+  static var A: SR_10084_E_11 = .A // expected-note {{found this candidate}} // expected-error {{invalid redeclaration of 'A'}} // expected-error {{ambiguous use of 'A'}}
 }
 
 enum SR_10084_E_12 {
-  static let A: SR_10084_E_12 = .A // expected-note {{found this candidate}} // expected-note {{'A' previously declared here}} // expected-error {{ambiguous use of 'A'}}
+  static var A: SR_10084_E_12 = .A // expected-note {{found this candidate}} // expected-note {{'A' previously declared here}} // expected-error {{ambiguous use of 'A'}}
   case A // expected-note {{found this candidate}} // expected-error {{invalid redeclaration of 'A'}}
 }
+
+enum SR_10084_E_13 {
+  case X // expected-note {{'X' previously declared here}}
+  struct X<T> {} // expected-error {{invalid redeclaration of 'X'}}
+}
+
+enum SR_10084_E_14 {
+  struct X<T> {} // expected-note {{'X' previously declared here}}
+  case X // expected-error {{invalid redeclaration of 'X'}}
+}
+
+enum SR_10084_E_15 {
+  case Y // expected-note {{'Y' previously declared here}}
+  typealias Y = Int // expected-error {{invalid redeclaration of 'Y'}}
+}
+
+enum SR_10084_E_16 {
+  typealias Z = Int // expected-note {{'Z' previously declared here}}
+  case Z // expected-error {{invalid redeclaration of 'Z'}}
+}