compiler_crashers: avoid using @c now that it's a real attribute

Author: xymus

validation-test/compiler_crashers_2/557cde75b2fa4b56.swift

@@ -1,4 +1,4 @@
 // {"kind":"typecheck","signature":"isParamListRepresentableInLanguage(swift::AbstractFunctionDecl const*, swift::ParameterList const*, swift::ObjCReason)","signatureAssert":"Assertion failed: (Ptr && \"Cannot dereference a null Type!\"), function operator->"}
 // RUN: not --crash %target-swift-frontend -typecheck %s
 // REQUIRES: objc_interop
-class a { @objc b(@c & d Int) @propertyWrapper enum c
+class a { @objc b(@e & d Int) @propertyWrapper enum e

validation-test/compiler_crashers_2/75874d2cf6f384c8.swift

@@ -3,9 +3,9 @@
 @propertyWrapper struct a<b{
          wrappedValue: b
        }
-        @propertyWrapper struct c<b{
+        @propertyWrapper struct e<b{
          wrappedValue: b
        }
            {
-               @c @a var value = if true
-                 let : c<a<Bool>> = _value
+               @e @a var value = if true
+                 let : e<a<Bool>> = _value

validation-test/compiler_crashers_2/8b3bbe2fe5878590.swift

@@ -1,10 +1,10 @@
 // {"kind":"typecheck","signature":"swift::TypeBase::getContextSubstitutions(swift::DeclContext const*, swift::GenericEnvironment*)","signatureAssert":"Assertion failed: (0 && \"Bad base type\"), function getContextSubstitutions"}
 // RUN: not --crash %target-swift-frontend -typecheck %s
 struct a< b {
-  @propertyWrapper struct c {
+  @propertyWrapper struct e {
     var wrappedValue
         projectedValue : a
                                         init(projectedValue
                                              a) {
-      func d(@c b) d($e
+      func d(@e b) d($e
                                                             : f

validation-test/compiler_crashers_2/d78fbedb0dfa9273.swift

@@ -1,5 +1,5 @@
 // {"kind":"typecheck","signature":"swift::TypeChecker::performTypoCorrection(swift::DeclContext*, swift::DeclRefKind, swift::Type, swift::optionset::OptionSet<swift::NameLookupFlags, unsigned int>, swift::TypoCorrectionResults&, swift::GenericSignature, unsigned int)","signatureAssert":"Assertion failed: (!baseTypeOrNull || !baseTypeOrNull->hasTypeParameter() || genericSig), function performTypoCorrection"}
 // RUN: not --crash %target-swift-frontend -typecheck %s
 enum a<b {
-  @propertyWrapper class c {wrappedValue:b var projectedValue: a? {
-      @c var wrappedValue: b wrappedValue.d
+  @propertyWrapper class e {wrappedValue:b var projectedValue: a? {
+      @e var wrappedValue: b wrappedValue.d