[SE-0458] Add fix-it for removing unnecessary "unsafe" keywords

Author: DougGregor

include/swift/AST/DiagnosticsSema.def

@@ -8242,9 +8242,9 @@ GROUPED_WARNING(unsafe_without_unsafe,StrictMemorySafety,none,
       "expression uses unsafe constructs but is not marked with 'unsafe'", ())
 GROUPED_WARNING(for_unsafe_without_unsafe,StrictMemorySafety,none,
       "for-in loop uses unsafe constructs but is not marked with 'unsafe'", ())
-WARNING(no_unsafe_in_unsafe,none,
+GROUPED_WARNING(no_unsafe_in_unsafe,StrictMemorySafety,none,
         "no unsafe operations occur within 'unsafe' expression", ())
-WARNING(no_unsafe_in_unsafe_for,none,
+GROUPED_WARNING(no_unsafe_in_unsafe_for,StrictMemorySafety,none,
         "no unsafe operations occur within 'unsafe' for-in loop", ())
 NOTE(make_subclass_unsafe,none,
      "make class %0 @unsafe to allow unsafe overrides of safe superclass methods",

lib/Sema/TypeCheckEffects.cpp

@@ -4420,7 +4420,8 @@ class CheckEffectsCoverage : public EffectsHandlingWalker<CheckEffectsCoverage>
       return;
     }
 
-    Ctx.Diags.diagnose(E->getUnsafeLoc(), diag::no_unsafe_in_unsafe);
+    Ctx.Diags.diagnose(E->getUnsafeLoc(), diag::no_unsafe_in_unsafe)
+      .fixItRemove(E->getUnsafeLoc());
   }
 
   std::pair<SourceLoc, std::string>

test/Unsafe/safe.swift

@@ -195,7 +195,7 @@ func unsafeFun() {
   acceptBoolsUnsafeLabel(unsafe: unsafe, unsafe)
 
   let color: Color
-  // expected-warning@+1{{no unsafe operations occur within 'unsafe' expression}}
+  // expected-warning@+1{{no unsafe operations occur within 'unsafe' expression}}{{11-18=}}
   color = unsafe .red
   _ = color