implementing changes and fixing unit tests

Author: dancamarotto

include/swift/AST/DiagnosticsSema.def

@@ -1048,6 +1048,8 @@ NOTE(single_confusable_character,none,
       (bool, StringRef, StringRef, StringRef, StringRef))
 ERROR(cannot_find_type_in_scope,none,
       "cannot find type %0 in scope", (DeclNameRef))
+ERROR(cannot_find_type_in_cast_expression,none,
+      "cast expression expects a type on its right-hand side (got: %0)", (DeclNameRef))
 ERROR(cannot_find_type_in_scope_did_you_mean,none,
       "cannot find type %0 in scope; did you mean to use '%1'?", (DeclNameRef, StringRef))
 NOTE(note_typo_candidate_implicit_member,none,

lib/Sema/TypeCheckType.cpp

@@ -1294,6 +1294,12 @@ static Type diagnoseUnknownType(TypeResolution resolution,
 
   // Unqualified lookup case.
   if (parentType.isNull()) {
+    if (resolution.getOptions().hasBase(TypeResolverContext::ExplicitCastExpr)) {
+      diags.diagnose(repr->getNameLoc(), diag::cannot_find_type_in_cast_expression,
+                     repr->getNameRef());
+      return ErrorType::get(ctx);
+    }
+    
     // Tailored diagnostic for custom attributes.
     if (resolution.getOptions().is(TypeResolverContext::CustomAttr)) {
       diags.diagnose(repr->getNameLoc(), diag::unknown_attribute,

test/ClangImporter/Darwin_test.swift

@@ -5,7 +5,7 @@
 import Darwin
 import MachO
 
-_ = nil as Fract? // expected-error{{cannot find type 'Fract' in scope}}
+_ = nil as Fract? // expected-error{{cast expression expects a type on its right-hand side (got: 'Fract')}}
 _ = nil as Darwin.Fract? // okay
 
 _ = 0 as OSErr
@@ -14,7 +14,7 @@ _ = 0 as UniChar
 
 _ = ProcessSerialNumber()
 
-_ = 0 as Byte // expected-error {{cannot find type 'Byte' in scope}} {{10-14=UInt8}}
+_ = 0 as Byte // expected-error {{cast expression expects a type on its right-hand side (got: 'Byte')}}
 Darwin.fakeAPIUsingByteInDarwin() as Int // expected-error {{cannot convert value of type 'UInt8' to type 'Int' in coercion}}
 
 _ = FALSE // expected-error {{cannot find 'FALSE' in scope}}

test/Constraints/casts.swift

@@ -741,3 +741,13 @@ do {
     assert(Set(b.map { $0 as A }) == Set(a)) // Ok
   }
 }
+
+// https://github.com/apple/swift/issues/68825
+do {
+  func x(a: Any) {
+    _ = a is a // expected-error {{cast expression expects a type on its right-hand side (got: 'a')}}
+    _ = a is a? // expected-error {{cast expression expects a type on its right-hand side (got: 'a')}}
+    _ = a as T // expected-error {{cast expression expects a type on its right-hand side (got: 'T')}}
+    _ = a is String // OK
+  }
+}

test/Parse/omit_return.swift

@@ -1710,7 +1710,7 @@ class CImplicitIdentityExpr { func gimme() -> CImplicitIdentityExpr { self } }
 class CImplicitDotSelfExpr { func gimme() -> CImplicitDotSelfExpr { self.self } }
 
 func badIs<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool {
-    value is type // expected-error {{cannot find type 'type' in scope}}
+    value is type // expected-error {{cast expression expects a type on its right-hand side (got: 'type')}}
 }
 
 

test/Parse/omit_return_fail.swift

@@ -1,7 +1,7 @@
 // RUN: %target-swift-frontend %s -typecheck -verify
 
 func badIs<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool {
-    value is type // expected-error {{cannot find type 'type' in scope}}
+    value is type // expected-error {{cast expression expects a type on its right-hand side (got: 'type')}}
 }
 
 func foo() -> Int {
@@ -10,7 +10,7 @@ func foo() -> Int {
 
 func badIs_ifdecl<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool {
     #if true
-    value is type // expected-error {{cannot find type 'type' in scope}}
+    value is type // expected-error {{cast expression expects a type on its right-hand side (got: 'type')}}
     #endif
 }
 

test/Parse/omit_return_ifdecl.swift

@@ -2432,7 +2432,7 @@ class CImplicitDotSelfExpr { func gimme() -> CImplicitDotSelfExpr { self.self }
 
 func badIs<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool {
     #if true
-    value is type // expected-error {{cannot find type 'type' in scope}}
+    value is type // expected-error {{cast expression expects a type on its right-hand side (got: 'type')}}
     #endif
 }