Merge pull request #68934 from dancamarotto/castmessage-whentypenotfound

Improve cast message when type not found

Author: xedin

include/swift/AST/DiagnosticsSema.def

@@ -1057,6 +1057,8 @@ 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,
+      "type-casting operator expects a type on its right-hand side (got: %kind0)", (const ValueDecl *))
 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

@@ -1423,6 +1423,19 @@ static Type diagnoseUnknownType(TypeResolution resolution,
 
       return I->second;
     }
+    
+    // type-casting operators such as 'is' and 'as'.
+    if (resolution.getOptions().is(TypeResolverContext::ExplicitCastExpr)) {
+      auto lookupResult = TypeChecker::lookupUnqualified(
+          dc, repr->getNameRef(), repr->getLoc(), lookupOptions);
+      if (!lookupResult.empty()) {
+        auto first = lookupResult.front().getValueDecl();
+        diags.diagnose(L, diag::cannot_find_type_in_cast_expression, first)
+          .highlight(R);
+        diags.diagnose(first, diag::decl_declared_here, first);
+        return ErrorType::get(ctx);
+      }
+    }
 
     diags.diagnose(L, diag::cannot_find_type_in_scope, repr->getNameRef())
         .highlight(R);

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) { // expected-note 2 {{'a' declared here}}
+    _ = a is a // expected-error {{type-casting operator expects a type on its right-hand side (got: parameter 'a')}}
+    _ = a as a // expected-error {{type-casting operator expects a type on its right-hand side (got: parameter 'a')}}
+    _ = a is Issue68825 // expected-error {{cannot find type 'Issue68825' in scope}}
+    _ = a is String // OK
+  }
+}

test/Parse/omit_return.swift

@@ -1709,8 +1709,8 @@ 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}}
+func badIs<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool { // expected-note {{'type' declared here}}
+    value is type // expected-error {{type-casting operator expects a type on its right-hand side (got: parameter 'type')}}
 }
 
 

test/Parse/omit_return_fail.swift

@@ -1,16 +1,16 @@
 // 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}}
+func badIs<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool { // expected-note {{'type' declared here}}
+    value is type // expected-error {{type-casting operator expects a type on its right-hand side (got: parameter 'type')}}
 }
 
 func foo() -> Int {
     return // expected-error {{non-void function should return a value}}
 }
 
-func badIs_ifdecl<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool {
+func badIs_ifdecl<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool { // expected-note {{'type' declared here}}
     #if true
-    value is type // expected-error {{cannot find type 'type' in scope}}
+    value is type // expected-error {{type-casting operator expects a type on its right-hand side (got: parameter 'type')}}
     #endif
 }
 

test/Parse/omit_return_ifdecl.swift

@@ -2430,9 +2430,9 @@ class CImplicitIdentityExpr { func gimme() -> CImplicitIdentityExpr { self } }
 
 class CImplicitDotSelfExpr { func gimme() -> CImplicitDotSelfExpr { self.self } }
 
-func badIs<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool {
+func badIs<T>(_ value: Any, anInstanceOf type: T.Type) -> Bool { // expected-note {{'type' declared here}}
     #if true
-    value is type // expected-error {{cannot find type 'type' in scope}}
+    value is type // expected-error {{type-casting operator expects a type on its right-hand side (got: parameter 'type')}}
     #endif
 }