Parse: Only accept certain literals as enum case raw values

Just checking for LiteralExpr is too broad, because Sema doesn't
know what to do with RegexLiteralExpr for example.

Author: slavapestov

lib/Parse/ParseDecl.cpp

@@ -9229,6 +9229,20 @@ ParserResult<EnumDecl> Parser::parseDeclEnum(ParseDeclOptions Flags,
   return DCC.fixupParserResult(Status, ED);
 }
 
+static bool isValidEnumRawValueLiteral(LiteralExpr *expr) {
+  if (expr == nullptr)
+    return false;
+
+  if (!isa<IntegerLiteralExpr>(expr) &&
+      !isa<FloatLiteralExpr>(expr) &&
+      !isa<StringLiteralExpr>(expr) &&
+      !isa<BooleanLiteralExpr>(expr) &&
+      !isa<NilLiteralExpr>(expr))
+    return false;
+
+  return true;
+}
+
 /// Parse a 'case' of an enum.
 ///
 /// \verbatim
@@ -9346,8 +9360,7 @@ Parser::parseDeclEnumCase(ParseDeclOptions Flags,
       }
       // The raw value must be syntactically a simple literal.
       LiteralRawValueExpr = dyn_cast<LiteralExpr>(RawValueExpr.getPtrOrNull());
-      if (!LiteralRawValueExpr
-          || isa<InterpolatedStringLiteralExpr>(LiteralRawValueExpr)) {
+      if (!isValidEnumRawValueLiteral(LiteralRawValueExpr)) {
         diagnose(RawValueExpr.getPtrOrNull()->getLoc(),
                  diag::nonliteral_enum_case_raw_value);
         LiteralRawValueExpr = nullptr;

test/decl/enum/invalid_raw_value.swift

@@ -0,0 +1,7 @@
+// RUN: %target-typecheck-verify-swift
+
+_ = a.init
+_ = b.init
+
+enum a : Int { case x = #/ /# }  // expected-error {{raw value for enum case must be a literal}}
+enum b : String { case x = #file }  // expected-error {{raw value for enum case must be a literal}}