[SE-0495] Make sure we can find imported C functions for @c @implementation

@c @implementation relies on matching the original C declaration. The
lookup for the original C declaration was doing the wrong kind of
lookup, meaning that it could only find the C declaration if it came
through a bridging header, and not through a normal module import.
Using unqualified lookup here finds the name appropriately.

Clarify the diagnostics here as well to not talk about umbrella and
bridging headers.

Fixes rdar://161909754.

Author: DougGregor

include/swift/AST/DiagnosticsSema.def

@@ -1879,12 +1879,12 @@ ERROR(objc_implementation_cannot_have_generics,none,
       "'@objc @implementation' cannot be used to implement %kind0",
       (ValueDecl *))
 ERROR(attr_objc_implementation_category_not_found,none,
-      "could not find category %0 on Objective-C class %1; make sure your "
-      "umbrella or bridging header imports the header that declares it",
+      "could not find category %0 on Objective-C class %1; make sure you "
+      "import the module or header that declares it",
       (Identifier, ValueDecl*))
 ERROR(attr_objc_implementation_func_not_found,none,
-      "could not find imported function '%0' matching %kind1; make sure your "
-      "umbrella or bridging header imports the header that declares it",
+      "could not find imported function '%0' matching %kind1; make sure you "
+      "import the module or header that declares it",
       (StringRef, ValueDecl*))
 NOTE(attr_objc_implementation_fixit_remove_category_name,none,
      "remove arguments to implement the main '@interface' for this class",

lib/AST/UnqualifiedLookup.cpp

@@ -483,6 +483,9 @@ void UnqualifiedLookupFactory::addImportedResults(const DeclContext *const dc) {
     nlOptions |= NL_ExcludeMacroExpansions;
   if (options.contains(Flags::ABIProviding))
     nlOptions |= NL_ABIProviding;
+  if (options.contains(Flags::IgnoreAccessControl))
+    nlOptions |= NL_IgnoreAccessControl;
+
   lookupInModule(dc, Name.getFullName(), CurModuleResults,
                  NLKind::UnqualifiedLookup, resolutionKind, dc,
                  Loc, nlOptions);

lib/ClangImporter/ClangImporter.cpp

@@ -6689,15 +6689,23 @@ static void lookupRelatedFuncs(AbstractFunctionDecl *func,
   else
     swiftName = func->getName();
 
-  NLOptions options = NL_IgnoreAccessControl | NL_IgnoreMissingImports;
   if (auto ty = func->getDeclContext()->getSelfNominalTypeDecl()) {
+    NLOptions options = NL_IgnoreAccessControl | NL_IgnoreMissingImports;
     ty->lookupQualified({ ty }, DeclNameRef(swiftName), func->getLoc(),
                         NL_QualifiedDefault | options, results);
   }
   else {
-    auto mod = func->getDeclContext()->getParentModule();
-    mod->lookupQualified(mod, DeclNameRef(swiftName), func->getLoc(),
-                         NL_RemoveOverridden | options, results);
+    ASTContext &ctx = func->getASTContext();
+    UnqualifiedLookupOptions options =
+      UnqualifiedLookupFlags::IgnoreAccessControl;
+    UnqualifiedLookupDescriptor descriptor(
+        DeclNameRef(ctx, Identifier(), swiftName), func->getDeclContext(),
+        func->getLoc(), options);
+    auto lookup = evaluateOrDefault(func->getASTContext().evaluator,
+                                    UnqualifiedLookupRequest{descriptor}, {});
+    for (const auto &result : lookup) {
+      results.push_back(result.getValueDecl());
+    }
   }
 }
 

test/NameLookup/Inputs/accessibility_other.swift

@@ -2,7 +2,7 @@ import has_accessibility
 
 public let a = 0 // expected-note * {{did you mean 'a'?}}
 internal let b = 0 // expected-note * {{did you mean 'b'?}}
-private let c = 0 // expected-note {{'c' declared here}}
+private let c = 0 // expected-note 2 {{'c' declared here}}
 
 extension Foo {
   public static func a() {}

test/NameLookup/accessibility.swift

@@ -37,7 +37,7 @@ markUsed(z) // expected-error {{cannot find 'z' in scope}}
 
 markUsed(a)
 markUsed(b)
-markUsed(c) // expected-error {{cannot find 'c' in scope}}
+markUsed(c) // expected-error {{'c' is inaccessible due to 'private' protection level}}
 
 Foo.x()
 Foo.y() // expected-error {{'y' is inaccessible due to 'internal' protection level}}
@@ -64,7 +64,7 @@ _ = PrivateInit() // expected-error {{'PrivateInit' initializer is inaccessible
 // TESTABLE: :[[@LINE-1]]:{{[^:]+}}: error: 'PrivateInit' initializer is inaccessible due to 'private' protection level
 
 var s = StructWithPrivateSetter()
-// expected-note@-1 3{{did you mean 's'?}}
+// expected-note@-1 2{{did you mean 's'?}}
 s.x = 42 // expected-error {{cannot assign to property: 'x' setter is inaccessible}}
 
 class Sub : Base {

test/decl/ext/Inputs/c_decls.h

@@ -0,0 +1 @@
+double c_function_returns_double(void);

test/decl/ext/Inputs/module.modulemap

@@ -0,0 +1,3 @@
+module ToBeImplemented {
+  header "c_decls.h"
+}

test/decl/ext/cdecl_official_implementation.swift

@@ -1,12 +1,18 @@
 // RUN: %target-typecheck-verify-swift -target %target-stable-abi-triple \
 // RUN:   -import-bridging-header %S/Inputs/objc_implementation.h \
+// RUN:   -I %S/Inputs \
 // RUN:   -disable-objc-interop \
 // RUN:   -enable-experimental-feature CImplementation \
 // RUN:   -enable-experimental-feature CDecl
 
 // REQUIRES: swift_feature_CImplementation
 // REQUIRES: swift_feature_CDecl
 
+import ToBeImplemented
+
+@implementation @c
+func c_function_returns_double() -> Double { 0 }
+
 @implementation @c
 func CImplFunc1(_: Int32) {
   // OK
@@ -24,7 +30,7 @@ func CImplFunc2(_: Int32) {
 
 @implementation @c
 func CImplFuncMissing(_: Int32) {
-  // expected-error@-2 {{could not find imported function 'CImplFuncMissing' matching global function 'CImplFuncMissing'; make sure your umbrella or bridging header imports the header that declares it}}
+  // expected-error@-2 {{could not find imported function 'CImplFuncMissing' matching global function 'CImplFuncMissing'; make sure you import the module or header that declares it}}
 }
 
 @implementation @c
@@ -39,13 +45,13 @@ func CImplFuncMismatch2(_: Int32) -> Float {
 
 @implementation @c(CImplFuncNameMismatch1)
 func mismatchedName1(_: Int32) {
-  // expected-error@-2 {{could not find imported function 'CImplFuncNameMismatch1' matching global function 'mismatchedName1'; make sure your umbrella or bridging header imports the header that declares it}}
+  // expected-error@-2 {{could not find imported function 'CImplFuncNameMismatch1' matching global function 'mismatchedName1'; make sure you import the module or header that declares it}}
   // FIXME: Improve diagnostic for a partial match.
 }
 
 @implementation @c(mismatchedName2)
 func CImplFuncNameMismatch2(_: Int32) {
-  // expected-error@-2 {{could not find imported function 'mismatchedName2' matching global function 'CImplFuncNameMismatch2'; make sure your umbrella or bridging header imports the header that declares it}}
+  // expected-error@-2 {{could not find imported function 'mismatchedName2' matching global function 'CImplFuncNameMismatch2'; make sure you import the module or header that declares it}}
   // FIXME: Improve diagnostic for a partial match.
 }
 
@@ -56,14 +62,14 @@ var cImplComputedGlobal1: Int32 {
   @implementation @c(CImplGetComputedGlobal1)
   get {
     // FIXME: Lookup for vars isn't working yet
-    // expected-error@-3 {{could not find imported function 'CImplGetComputedGlobal1' matching getter for var 'cImplComputedGlobal1'; make sure your umbrella or bridging header imports the header that declares it}}
+    // expected-error@-3 {{could not find imported function 'CImplGetComputedGlobal1' matching getter for var 'cImplComputedGlobal1'; make sure you import the module or header that declares it}}
     return 0
   }
 
   @implementation @c(CImplSetComputedGlobal1)
   set {
     // FIXME: Lookup for vars isn't working yet
-    // expected-error@-3 {{could not find imported function 'CImplSetComputedGlobal1' matching setter for var 'cImplComputedGlobal1'; make sure your umbrella or bridging header imports the header that declares it}}
+    // expected-error@-3 {{could not find imported function 'CImplSetComputedGlobal1' matching setter for var 'cImplComputedGlobal1'; make sure you import the module or header that declares it}}
     print(newValue)
   }
 }
@@ -77,6 +83,6 @@ extension CImplStruct {
     // FIXME: Add underlying support for this
     // expected-error@-3 {{@c can only be applied to global functions}}
     // FIXME: Lookup in an enclosing type is not working yet
-    // expected-error@-5 {{could not find imported function 'CImplStructStaticFunc1' matching static method 'staticFunc1'; make sure your umbrella or bridging header imports the header that declares it}}
+    // expected-error@-5 {{could not find imported function 'CImplStructStaticFunc1' matching static method 'staticFunc1'; make sure you import the module or header that declares it}}
   }
 }

test/decl/ext/objc_implementation.swift

@@ -503,7 +503,7 @@ protocol EmptySwiftProto {}
 // expected-warning@-1 {{extension with Objective-C category name 'PresentAdditions' conflicts with previous extension with the same category name; this is an error in the Swift 6 language mode}}
 
 @objc(MissingAdditions) @implementation extension ObjCClass {}
-// expected-error@-1 {{could not find category 'MissingAdditions' on Objective-C class 'ObjCClass'; make sure your umbrella or bridging header imports the header that declares it}}
+// expected-error@-1 {{could not find category 'MissingAdditions' on Objective-C class 'ObjCClass'; make sure you import the module or header that declares it}}
 // expected-note@-2 {{remove arguments to implement the main '@interface' for this class}} {{6-24=}}
 
 @objc @implementation extension ObjCStruct {}
@@ -558,7 +558,7 @@ func CImplFunc2(_: Int32) {
 
 @implementation @_cdecl("CImplFuncMissing")
 func CImplFuncMissing(_: Int32) {
-  // expected-error@-2 {{could not find imported function 'CImplFuncMissing' matching global function 'CImplFuncMissing'; make sure your umbrella or bridging header imports the header that declares it}}
+  // expected-error@-2 {{could not find imported function 'CImplFuncMissing' matching global function 'CImplFuncMissing'; make sure you import the module or header that declares it}}
 }
 
 @implementation @_cdecl("CImplFuncMismatch1")
@@ -614,13 +614,13 @@ func CImplFuncMismatch6a(_: Int32) -> Any! {
 
 @implementation @_cdecl("CImplFuncNameMismatch1")
 func mismatchedName1(_: Int32) {
-  // expected-error@-2 {{could not find imported function 'CImplFuncNameMismatch1' matching global function 'mismatchedName1'; make sure your umbrella or bridging header imports the header that declares it}}
+  // expected-error@-2 {{could not find imported function 'CImplFuncNameMismatch1' matching global function 'mismatchedName1'; make sure you import the module or header that declares it}}
   // FIXME: Improve diagnostic for a partial match.
 }
 
 @implementation @_cdecl("mismatchedName2")
 func CImplFuncNameMismatch2(_: Int32) {
-  // expected-error@-2 {{could not find imported function 'mismatchedName2' matching global function 'CImplFuncNameMismatch2'; make sure your umbrella or bridging header imports the header that declares it}}
+  // expected-error@-2 {{could not find imported function 'mismatchedName2' matching global function 'CImplFuncNameMismatch2'; make sure you import the module or header that declares it}}
   // FIXME: Improve diagnostic for a partial match.
 }
 
@@ -631,14 +631,14 @@ var cImplComputedGlobal1: Int32 {
   @implementation @_cdecl("CImplGetComputedGlobal1")
   get {
     // FIXME: Lookup for vars isn't working yet
-    // expected-error@-3 {{could not find imported function 'CImplGetComputedGlobal1' matching getter for var 'cImplComputedGlobal1'; make sure your umbrella or bridging header imports the header that declares it}}
+    // expected-error@-3 {{could not find imported function 'CImplGetComputedGlobal1' matching getter for var 'cImplComputedGlobal1'; make sure you import the module or header that declares it}}
     return 0
   }
 
   @implementation @_cdecl("CImplSetComputedGlobal1")
   set {
     // FIXME: Lookup for vars isn't working yet
-    // expected-error@-3 {{could not find imported function 'CImplSetComputedGlobal1' matching setter for var 'cImplComputedGlobal1'; make sure your umbrella or bridging header imports the header that declares it}}
+    // expected-error@-3 {{could not find imported function 'CImplSetComputedGlobal1' matching setter for var 'cImplComputedGlobal1'; make sure you import the module or header that declares it}}
     print(newValue)
   }
 }
@@ -652,7 +652,7 @@ extension CImplStruct {
     // FIXME: Add underlying support for this
     // expected-error@-3 {{@_cdecl can only be applied to global functions}}
     // FIXME: Lookup in an enclosing type is not working yet
-    // expected-error@-5 {{could not find imported function 'CImplStructStaticFunc1' matching static method 'staticFunc1'; make sure your umbrella or bridging header imports the header that declares it}}
+    // expected-error@-5 {{could not find imported function 'CImplStructStaticFunc1' matching static method 'staticFunc1'; make sure you import the module or header that declares it}}
   }
 }
 

test/decl/ext/objc_implementation_early_adopter.swift

@@ -507,7 +507,7 @@ protocol EmptySwiftProto {}
 // expected-warning@-1 {{extension with Objective-C category name 'PresentAdditions' conflicts with previous extension with the same category name; this is an error in the Swift 6 language mode}}
 
 @_objcImplementation(MissingAdditions) extension ObjCClass {}
-// expected-error@-1 {{could not find category 'MissingAdditions' on Objective-C class 'ObjCClass'; make sure your umbrella or bridging header imports the header that declares it}}
+// expected-error@-1 {{could not find category 'MissingAdditions' on Objective-C class 'ObjCClass'; make sure you import the module or header that declares it}}
 // expected-note@-2 {{remove arguments to implement the main '@interface' for this class}} {{21-39=}}
 
 @_objcImplementation extension ObjCStruct {}
@@ -549,7 +549,7 @@ func CImplFunc2(_: Int32) {
 
 @_objcImplementation @_cdecl("CImplFuncMissing")
 func CImplFuncMissing(_: Int32) {
-  // expected-error@-2 {{could not find imported function 'CImplFuncMissing' matching global function 'CImplFuncMissing'; make sure your umbrella or bridging header imports the header that declares it}}
+  // expected-error@-2 {{could not find imported function 'CImplFuncMissing' matching global function 'CImplFuncMissing'; make sure you import the module or header that declares it}}
 }
 
 @_objcImplementation @_cdecl("CImplFuncMismatch1")
@@ -605,13 +605,13 @@ func CImplFuncMismatch6a(_: Int32) -> Any! {
 
 @_objcImplementation @_cdecl("CImplFuncNameMismatch1")
 func mismatchedName1(_: Int32) {
-  // expected-error@-2 {{could not find imported function 'CImplFuncNameMismatch1' matching global function 'mismatchedName1'; make sure your umbrella or bridging header imports the header that declares it}}
+  // expected-error@-2 {{could not find imported function 'CImplFuncNameMismatch1' matching global function 'mismatchedName1'; make sure you import the module or header that declares it}}
   // FIXME: Improve diagnostic for a partial match.
 }
 
 @_objcImplementation @_cdecl("mismatchedName2")
 func CImplFuncNameMismatch2(_: Int32) {
-  // expected-error@-2 {{could not find imported function 'mismatchedName2' matching global function 'CImplFuncNameMismatch2'; make sure your umbrella or bridging header imports the header that declares it}}
+  // expected-error@-2 {{could not find imported function 'mismatchedName2' matching global function 'CImplFuncNameMismatch2'; make sure you import the module or header that declares it}}
   // FIXME: Improve diagnostic for a partial match.
 }
 
@@ -622,14 +622,14 @@ var cImplComputedGlobal1: Int32 {
   @_objcImplementation @_cdecl("CImplGetComputedGlobal1")
   get {
     // FIXME: Lookup for vars isn't working yet
-    // expected-error@-3 {{could not find imported function 'CImplGetComputedGlobal1' matching getter for var 'cImplComputedGlobal1'; make sure your umbrella or bridging header imports the header that declares it}}
+    // expected-error@-3 {{could not find imported function 'CImplGetComputedGlobal1' matching getter for var 'cImplComputedGlobal1'; make sure you import the module or header that declares it}}
     return 0
   }
 
   @_objcImplementation @_cdecl("CImplSetComputedGlobal1")
   set {
     // FIXME: Lookup for vars isn't working yet
-    // expected-error@-3 {{could not find imported function 'CImplSetComputedGlobal1' matching setter for var 'cImplComputedGlobal1'; make sure your umbrella or bridging header imports the header that declares it}}
+    // expected-error@-3 {{could not find imported function 'CImplSetComputedGlobal1' matching setter for var 'cImplComputedGlobal1'; make sure you import the module or header that declares it}}
     print(newValue)
   }
 }
@@ -643,7 +643,7 @@ extension CImplStruct {
     // FIXME: Add underlying support for this
     // expected-error@-3 {{@_cdecl can only be applied to global functions}}
     // FIXME: Lookup in an enclosing type is not working yet
-    // expected-error@-5 {{could not find imported function 'CImplStructStaticFunc1' matching static method 'staticFunc1'; make sure your umbrella or bridging header imports the header that declares it}}
+    // expected-error@-5 {{could not find imported function 'CImplStructStaticFunc1' matching static method 'staticFunc1'; make sure you import the module or header that declares it}}
   }
 }