[CSDiagnostics] Extract diagnostic for CoerceExpr to function

Author: LucianoPAlmeida

lib/Sema/CSDiagnostics.cpp

@@ -1854,21 +1854,8 @@ bool ContextualFailure::diagnoseAsError() {
       return true;
     }
 
-    if (auto *coerceExpr = dyn_cast<CoerceExpr>(anchor)) {
-      auto fromType = getFromType();
-      auto toType = getType(coerceExpr->getCastTypeLoc());
-      auto diagnostic =
-          getDiagnosticFor(CTP_CoerceOperand,
-                           /*forProtocol=*/toType->isAnyExistentialType());
-      
-      auto diag =
-          emitDiagnostic(anchor->getLoc(), *diagnostic, fromType, toType);
-      diag.highlight(anchor->getSourceRange());
-
-      (void)tryFixIts(diag);
-      
+    if (diagnoseConversionInCoercion())
       return true;
-    }
 
     return false;
   }
@@ -2236,6 +2223,28 @@ bool ContextualFailure::diagnoseMissingFunctionCall() const {
   return true;
 }
 
+bool ContextualFailure::diagnoseConversionInCoercion() const {
+  auto *anchor = getAnchor();
+  
+  if (auto *coerceExpr = dyn_cast<CoerceExpr>(anchor)) {
+    auto fromType = getFromType();
+    auto toType = getType(coerceExpr->getCastTypeLoc());
+    auto diagnostic =
+        getDiagnosticFor(CTP_CoerceOperand,
+                         /*forProtocol=*/toType->isAnyExistentialType());
+    
+    auto diag =
+        emitDiagnostic(anchor->getLoc(), *diagnostic, fromType, toType);
+    diag.highlight(anchor->getSourceRange());
+
+    (void)tryFixIts(diag);
+    
+    return true;
+  }
+
+  return false;
+}
+
 bool ContextualFailure::diagnoseConversionToBool() const {
   auto toType = getToType();
   if (!toType->isBool())
@@ -2581,6 +2590,10 @@ bool ContextualFailure::trySequenceSubsequenceFixIts(
   if (getFromType()->isEqual(Substring)) {
     if (getToType()->isEqual(String)) {
       auto *anchor = getAnchor()->getSemanticsProvidingExpr();
+      if (auto *CE = dyn_cast<CoerceExpr>(anchor)) {
+        anchor = CE->getSubExpr();
+      }
+      
       auto range = anchor->getSourceRange();
       diagnostic.fixItInsert(range.Start, "String(");
       diagnostic.fixItInsertAfter(range.End, ")");

lib/Sema/CSDiagnostics.h

@@ -554,6 +554,9 @@ class ContextualFailure : public FailureDiagnostic {
 
   /// If we're trying to convert something to `nil`.
   bool diagnoseConversionToNil() const;
+  
+  /// Diagnose failed conversion in a `CoerceExpr`.
+  bool diagnoseConversionInCoercion() const;
 
   // If we're trying to convert something of type "() -> T" to T,
   // then we probably meant to call the value.

test/Parse/recovery.swift

@@ -619,9 +619,11 @@ class WrongInheritanceClause6(Int {}
 class WrongInheritanceClause7<T>(Int where T:AnyObject {}
 
 // <rdar://problem/18502220> [swift-crashes 078] parser crash on invalid cast in sequence expr
-Base=1 as Base=1  // expected-error {{cannot convert value of type 'Int' to type 'Base' in coercion}}
-
-
+Base=1 as Base=1 // expected-error{{cannot convert value of type 'Int' to type 'Base' in coercion}}
+// expected-error@-1 {{cannot assign to immutable expression of type 'Base.Type'}}
+// expected-error@-2 {{left side of mutating operator has immutable type 'Base'}}
+// expected-error@-3 {{cannot assign value of type '()' to type 'Base.Type'}}
+// expected-error@-4 {{cannot assign value of type 'Int' to type 'Base'}}
 
 // <rdar://problem/18634543> Parser hangs at swift::Parser::parseType
 public enum TestA {