sema: set locator properly when diagnosing constness mismatches

rdar://90210674

Author: nkcsgexi

include/swift/AST/Types.h

@@ -2088,7 +2088,7 @@ class ParameterTypeFlags {
     return value.toRaw() != other.value.toRaw();
   }
 
-  uint8_t toRaw() const { return value.toRaw(); }
+  uint16_t toRaw() const { return value.toRaw(); }
 };
 
 class YieldTypeFlags {

lib/Sema/CSSimplify.cpp

@@ -1932,7 +1932,7 @@ static ConstraintSystem::TypeMatchResult matchCallArguments(
             locator->getAnchor().isExpr(ExprKind::UnresolvedMemberChainResult)) {
           locator =
             cs.getConstraintLocator(cast<UnresolvedMemberChainResultExpr>(
-              locator->getAnchor().get<Expr*>())->getChainBase());
+              locator->getAnchor().get<Expr*>())->getSubExpr());
         }
         cs.recordFix(NotCompileTimeConst::create(cs, paramTy, locator));
       }

test/Sema/const_enum_elements2.swift

@@ -0,0 +1,12 @@
+// RUN: %target-typecheck-verify-swift
+
+enum E {
+  case a
+  case b(Int)
+
+  var c: E { .b(42) }
+}
+
+func test(_: _const E) {}
+
+test(.a.c) // expected-error {{expect a compile-time constant literal}}