[Concurrency] Drop "get" prefix when importing Objective-C methods as async.

Implements rdar://70506634.

Author: DougGregor

lib/ClangImporter/ImportName.cpp

@@ -1189,6 +1189,7 @@ Optional<ForeignAsyncConvention::Info>
 NameImporter::considerAsyncImport(
     const clang::ObjCMethodDecl *clangDecl,
     StringRef &baseName,
+    SmallVectorImpl<char> &baseNameScratch,
     SmallVectorImpl<StringRef> &paramNames,
     ArrayRef<const clang::ParmVarDecl *> params,
     bool isInitializer, bool hasCustomName,
@@ -1224,6 +1225,17 @@ NameImporter::considerAsyncImport(
     return None;
   }
 
+  // If there's no custom name, and the base name starts with "get", drop the
+  // get.
+  if (!hasCustomName) {
+    StringRef currentBaseName = newBaseName ? *newBaseName : baseName;
+    if (currentBaseName.size() > 3 &&
+        camel_case::getFirstWord(currentBaseName) == "get") {
+      newBaseName = camel_case::toLowercaseInitialisms(
+          currentBaseName.substr(3), baseNameScratch);
+    }
+  }
+
   // Used for returns once we've determined that the method cannot be
   // imported as async, even though it has what looks like a completion handler
   // parameter.
@@ -1461,6 +1473,7 @@ ImportedName NameImporter::importNameImpl(const clang::NamedDecl *D,
   }
 
   // If we have a swift_name attribute, use that.
+  SmallString<32> asyncBaseNameScratch;
   if (auto *nameAttr = findSwiftNameAttr(D, version)) {
     bool skipCustomName = false;
 
@@ -1539,9 +1552,9 @@ ImportedName NameImporter::importNameImpl(const clang::NamedDecl *D,
 
         if (version.supportsConcurrency()) {
           if (auto asyncInfo = considerAsyncImport(
-                  method, parsedName.BaseName, parsedName.ArgumentLabels,
-                  params, isInitializer, /*hasCustomName=*/true,
-                  result.getErrorInfo())) {
+                  method, parsedName.BaseName, asyncBaseNameScratch,
+                  parsedName.ArgumentLabels, params, isInitializer,
+                  /*hasCustomName=*/true, result.getErrorInfo())) {
             result.info.hasAsyncInfo = true;
             result.info.asyncInfo = *asyncInfo;
 
@@ -1816,8 +1829,8 @@ ImportedName NameImporter::importNameImpl(const clang::NamedDecl *D,
     if (version.supportsConcurrency() &&
         result.info.accessorKind == ImportedAccessorKind::None) {
       if (auto asyncInfo = considerAsyncImport(
-              objcMethod, baseName, argumentNames, params, isInitializer,
-              /*hasCustomName=*/false,
+              objcMethod, baseName, asyncBaseNameScratch,
+              argumentNames, params, isInitializer, /*hasCustomName=*/false,
               result.getErrorInfo())) {
         result.info.hasAsyncInfo = true;
         result.info.asyncInfo = *asyncInfo;

lib/ClangImporter/ImportName.h

@@ -456,6 +456,7 @@ class NameImporter {
   Optional<ForeignAsyncConvention::Info>
   considerAsyncImport(const clang::ObjCMethodDecl *clangDecl,
                       StringRef &baseName,
+                      SmallVectorImpl<char> &baseNameScratch,
                       SmallVectorImpl<StringRef> &paramNames,
                       ArrayRef<const clang::ParmVarDecl *> params,
                       bool isInitializer, bool hasCustomName,

test/ClangImporter/objc_async.swift

@@ -18,6 +18,8 @@ func testSlowServer(slowServer: SlowServer) async throws {
   // still async version...
   let _: Int = slowServer.doSomethingConflicted("thinking")
   // expected-error@-1{{call is 'async' but is not marked with 'await'}}
+
+  let _: String? = await try slowServer.fortune()
 }
 
 func testSlowServerSynchronous(slowServer: SlowServer) {

test/Inputs/clang-importer-sdk/usr/include/ObjCConcurrency.h

@@ -10,6 +10,7 @@
 -(void)findAnswerAsynchronously:(void (^)(NSString *_Nullable, NSError * _Nullable))handler __attribute__((swift_name("findAnswer(completionHandler:)")));
 -(BOOL)findAnswerFailinglyWithError:(NSError * _Nullable * _Nullable)error completion:(void (^)(NSString *_Nullable, NSError * _Nullable))handler __attribute__((swift_name("findAnswerFailingly(completionHandler:)")));
 -(void)doSomethingFun:(NSString *)operation then:(void (^)(void))completionHandler;
+-(void)getFortuneWithCompletionHandler:(void (^)(NSString *_Nullable, NSError * _Nullable))handler;
 @property(readwrite) void (^completionHandler)(NSInteger);
 
 -(void)doSomethingConflicted:(NSString *)operation completionHandler:(void (^)(NSInteger))handler;