Sema: Simplify recursion breaking for variables

We can use the existing logic for checking recursion in
declaration validation. This eliminates some bogus
diagnostics and allows some weird logic to be removed
from typo correction.

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -666,10 +666,6 @@ NOTE(note_typo_candidate_implicit_member,none,
      "did you mean the implicitly-synthesized %1 '%0'?", (StringRef, StringRef))
 NOTE(note_remapped_type,none,
      "did you mean to use '%0'?", (StringRef))
-ERROR(identifier_init_failure,none,
-      "could not infer type for %0", (Identifier))
-ERROR(pattern_used_in_type,none,
-      "%0 used within its own type", (Identifier))
 NOTE(note_module_as_type,none,
      "cannot use module %0 as a type", (Identifier))
 

lib/Sema/TypeCheckDecl.cpp

@@ -7036,6 +7036,10 @@ void TypeChecker::validateDecl(ValueDecl *D) {
   case DeclKind::Param: {
     auto VD = cast<VarDecl>(D);
 
+    if (PatternBindingDecl *PBD = VD->getParentPatternBinding())
+      if (PBD->isBeingValidated())
+        return;
+
     D->setIsBeingValidated();
 
     if (!VD->hasInterfaceType()) {
@@ -7046,25 +7050,12 @@ void TypeChecker::validateDecl(ValueDecl *D) {
         }
         recordSelfContextType(cast<AbstractFunctionDecl>(VD->getDeclContext()));
       } else if (PatternBindingDecl *PBD = VD->getParentPatternBinding()) {
-        if (PBD->isBeingValidated()) {
-          diagnose(VD, diag::pattern_used_in_type, VD->getName());
-
-        } else {
-          validatePatternBindingEntries(*this, PBD);
-        }
+        validatePatternBindingEntries(*this, PBD);
 
         auto parentPattern = VD->getParentPattern();
         if (PBD->isInvalid() || !parentPattern->hasType()) {
           parentPattern->setType(ErrorType::get(Context));
           setBoundVarsTypeError(parentPattern, Context);
-          
-          // If no type has been set for the initializer, we need to diagnose
-          // the failure.
-          if (VD->getParentInitializer() &&
-              !VD->getParentInitializer()->getType()) {
-            diagnose(parentPattern->getLoc(), diag::identifier_init_failure,
-                     parentPattern->getBoundName());
-          }
         }
       } else {
         // FIXME: This case is hit when code completion occurs in a function
@@ -7172,6 +7163,14 @@ void TypeChecker::validateDecl(ValueDecl *D) {
     auto *FD = cast<FuncDecl>(D);
     assert(!FD->hasInterfaceType());
 
+    // Bail out if we're in a recursive validation situation.
+    if (auto accessor = dyn_cast<AccessorDecl>(FD)) {
+      auto *storage = accessor->getStorage();
+      validateDecl(storage);
+      if (!storage->hasValidSignature())
+        return;
+    }
+
     checkDeclAttributesEarly(FD);
     computeAccessLevel(FD);
 
@@ -7208,7 +7207,6 @@ void TypeChecker::validateDecl(ValueDecl *D) {
     // FIXME: should this include the generic signature?
     if (auto accessor = dyn_cast<AccessorDecl>(FD)) {
       auto storage = accessor->getStorage();
-      validateDecl(storage);
 
       // Note that it's important for correctness that we're filling in
       // empty TypeLocs, because otherwise revertGenericFuncSignature might

test/ClangImporter/MixedSource/can_import_objc_idempotent.swift

@@ -26,15 +26,15 @@
 #endif
 
 #if canImport(CoreGraphics)
-  let square = CGRect(x: 100, y: 100, width: 100, height: 100) // expected-error {{use of unresolved identifier 'CGRect'}}
-  // expected-error@-1 {{'square' used within its own type}}
-  // expected-error@-2 {{could not infer type for 'square'}}
+  let square = CGRect(x: 100, y: 100, width: 100, height: 100)
+  // expected-error@-1 {{use of unresolved identifier 'CGRect'}}
+  // expected-note@-2 {{'square' declared here}}
+
   let (r, s) = square.divided(atDistance: 50, from: .minXEdge)
+  // expected-error@-1 {{ambiguous use of 'square'}}
 #endif
 
 #if canImport(MixedWithHeader)
 let object = NSObject() // expected-error {{use of unresolved identifier 'NSObject'}}
-  // expected-error@-1 {{'object' used within its own type}}
-  // expected-error@-2 {{could not infer type for 'object'}}
 let someAPI = Derived() // expected-error {{use of unresolved identifier 'Derived'}}
 #endif

test/NameBinding/scope_map_lookup.swift

@@ -118,6 +118,6 @@ protocol Fooable {
 struct S<T> // expected-error{{expected '{' in struct}}
 extension S // expected-error{{expected '{' in extension}}
 
-let a = b ; let b = a // expected-error{{could not infer type for 'a'}} 
-// expected-error@-1 {{'a' used within its own type}}
-// FIXME: That second error is bogus.
+let a = b ; let b = a
+// expected-note@-1 {{'a' declared here}}
+// expected-error@-2 {{ambiguous use of 'a'}}

test/decl/var/variables.swift

@@ -65,9 +65,9 @@ class SomeClass {}
 // <rdar://problem/16877304> weak let's should be rejected
 weak let V = SomeClass()  // expected-error {{'weak' must be a mutable variable, because it may change at runtime}}
 
-let a = b ; let b = a // expected-error{{could not infer type for 'a'}} 
-// expected-error@-1 {{'a' used within its own type}}
-// FIXME: That second error is bogus.
+let a = b ; let b = a
+// expected-note@-1 {{'a' declared here}}
+// expected-error@-2 {{ambiguous use of 'a'}}
 
 // <rdar://problem/17501765> Swift should warn about immutable default initialized values
 let uselessValue : String?