[FixCode] Using coercion (as) instead of forced-coercion (as!) when the former is applicable. rdar://27683732 (#4008)

This fixit is migration-critical to help users call functions now take 'Any' or 'NSHashble' while used to take 'AnyObject'. We insert coercion to the original call sites.

Author: nkcsgexi

lib/Sema/CSDiag.cpp

@@ -3579,15 +3579,21 @@ static bool tryIntegerCastFixIts(InFlightDiagnostic &diag,
 static bool
 addTypeCoerceFixit(InFlightDiagnostic &diag, ConstraintSystem *CS,
                    Type fromType, Type toType, Expr *expr) {
-  if (CS->getTypeChecker().typeCheckCheckedCast(fromType, toType, CS->DC,
-      SourceLoc(), SourceRange(), SourceRange(), [](Type T) { return false; },
-      true) != CheckedCastKind::Unresolved) {
+  CheckedCastKind Kind =
+    CS->getTypeChecker().typeCheckCheckedCast(fromType, toType, CS->DC,
+                                              SourceLoc(), SourceRange(),
+                                              SourceRange(),
+                                              [](Type T) { return false; },
+                                              /*suppressDiagnostics*/ true);
+  if (Kind != CheckedCastKind::Unresolved) {
     SmallString<32> buffer;
     llvm::raw_svector_ostream OS(buffer);
     toType->print(OS);
     diag.fixItInsert(Lexer::getLocForEndOfToken(CS->DC->getASTContext().SourceMgr,
                                                 expr->getEndLoc()),
-                     (llvm::Twine(" as! ") + OS.str()).str());
+                     (llvm::Twine(Kind == CheckedCastKind::Coercion ? " as " :
+                                                                      " as! ") +
+                      OS.str()).str());
     return true;
   }
   return false;

test/Sema/diag_type_conversion.swift

@@ -1,4 +1,8 @@
-// RUN: %target-parse-verify-swift
+// RUN: %target-parse-verify-swift %clang-importer-sdk
+
+// REQUIRES: objc_interop
+
+import Foundation
 
 func foo1(_ a: [Int]) {}
 func foo2(_ a : UnsafePointer<Int>) {}
@@ -34,3 +38,13 @@ func foo9(s : S1) {}
 func foo10(p : P1) {
   foo9(s : p) // expected-error {{cannot convert value of type 'P1' to expected argument type 'S1'}} {{13-13= as! S1}}
 }
+
+func foo11(a : [AnyHashable]) {}
+func foo12(b : [NSObject]) {
+  foo11(a : b) // expected-error {{cannot convert value of type '[NSObject]' to expected argument type '[AnyHashable]'}} {{14-14= as [AnyHashable]}}
+}
+
+func foo13(a : [AnyHashable : Any]) {}
+func foo14(b : [NSObject : AnyObject]) {
+  foo13(a : b ) // expected-error {{cannot convert value of type '[NSObject : AnyObject]' to expected argument type '[AnyHashable : Any]'}} {{14-14= as [AnyHashable : Any]}}
+}