Ensure that we record the @unsafe for conformances introduced via extensions

Author: DougGregor

lib/AST/ConformanceLookupTable.cpp

@@ -166,13 +166,17 @@ namespace {
     /// The location of the "preconcurrency" attribute if present.
     const SourceLoc preconcurrencyLoc;
 
+    /// The location of the "unsafe" attribute if present.
+    const SourceLoc unsafeLoc;
+
     ConformanceConstructionInfo() { }
 
     ConformanceConstructionInfo(ProtocolDecl *item, SourceLoc loc,
                                 SourceLoc uncheckedLoc,
-                                SourceLoc preconcurrencyLoc)
+                                SourceLoc preconcurrencyLoc,
+                                SourceLoc unsafeLoc)
         : Located(item, loc), uncheckedLoc(uncheckedLoc),
-          preconcurrencyLoc(preconcurrencyLoc) {}
+          preconcurrencyLoc(preconcurrencyLoc), unsafeLoc(unsafeLoc) {}
   };
 }
 
@@ -228,7 +232,7 @@ void ConformanceLookupTable::forEachInStage(ConformanceStage stage,
       registerProtocolConformances(next, conformances);
       for (auto conf : conformances) {
         protocols.push_back(
-            {conf->getProtocol(), SourceLoc(), SourceLoc(), SourceLoc()});
+            {conf->getProtocol(), SourceLoc(), SourceLoc(), SourceLoc(), SourceLoc()});
       }
     } else if (next->getParentSourceFile() ||
                next->getParentModule()->isBuiltinModule()) {
@@ -238,7 +242,8 @@ void ConformanceLookupTable::forEachInStage(ConformanceStage stage,
                getDirectlyInheritedNominalTypeDecls(next, inverses, anyObject)) {
         if (auto proto = dyn_cast<ProtocolDecl>(found.Item))
           protocols.push_back(
-              {proto, found.Loc, found.uncheckedLoc, found.preconcurrencyLoc});
+              {proto, found.Loc, found.uncheckedLoc,
+               found.preconcurrencyLoc, found.unsafeLoc});
       }
     }
 
@@ -343,7 +348,8 @@ void ConformanceLookupTable::updateLookupTable(NominalTypeDecl *nominal,
             addProtocol(
                 locAndProto.Item, locAndProto.Loc,
                 source.withUncheckedLoc(locAndProto.uncheckedLoc)
-                      .withPreconcurrencyLoc(locAndProto.preconcurrencyLoc));
+                      .withPreconcurrencyLoc(locAndProto.preconcurrencyLoc)
+                      .withUnsafeLoc(locAndProto.unsafeLoc));
         });
     break;
 

test/Unsafe/safe.swift

@@ -60,6 +60,18 @@ struct HasProperties {
   }()
 }
 
+protocol P { }
+
+extension Int: @unsafe P { }
+
+func acceptP(_: some P) { }
+
+func testConformance(i: Int) {
+  // expected-warning@+1{{expression uses unsafe constructs but is not marked with 'unsafe'}}
+  acceptP(i) // expected-note{{@unsafe conformance of 'Int' to protocol 'P' involves unsafe code}}
+}
+
+
 // Parsing of `unsafe` expressions.
 func testUnsafePositionError() -> Int {
   return 3 + unsafe unsafeInt() // expected-error{{'unsafe' cannot appear to the right of a non-assignment operator}}