[Sema] Avoid applying diagnostic hack to caller-side expression macros

We can't assume that type-checking the expression macro in the
parameter will also fail if it fails at the call site since e.g
name lookup may differ. Make sure we only apply this logic to simple
literals.

rdar://154771596

Author: hamishknight

lib/Sema/TypeCheckExpr.cpp

@@ -774,14 +774,30 @@ Expr *CallerSideDefaultArgExprRequest::evaluate(
   if (!TypeChecker::typeCheckParameterDefault(initExpr, dc, paramTy,
                                               param->isAutoClosure(),
                                               /*atCallerSide=*/true)) {
-    if (param->hasDefaultExpr()) {
+    auto isSimpleLiteral = [&]() -> bool {
+      switch (param->getDefaultArgumentKind()) {
+#define MAGIC_IDENTIFIER(NAME, STRING) \
+      case DefaultArgumentKind::NAME: return true;
+#include "swift/AST/MagicIdentifierKinds.def"
+      case DefaultArgumentKind::NilLiteral:
+      case DefaultArgumentKind::EmptyArray:
+      case DefaultArgumentKind::EmptyDictionary:
+        return true;
+      default:
+        return false;
+      }
+    };
+    if (param->hasDefaultExpr() && isSimpleLiteral()) {
       // HACK: If we were unable to type-check the default argument in context,
       // then retry by type-checking it within the parameter decl, which should
       // also fail. This will present the user with a better error message and
       // allow us to avoid diagnosing on each call site.
+      // Note we can't do this for expression macros since name lookup may
+      // differ at the call side vs the declaration. We can however do it for
+      // simple literals.
       transaction.abort();
       (void)param->getTypeCheckedDefaultExpr();
-      assert(ctx.Diags.hadAnyError());
+      ASSERT(ctx.Diags.hadAnyError());
     }
     return new (ctx) ErrorExpr(initExpr->getSourceRange(), paramTy);
   }

test/Macros/rdar154771596.swift

@@ -0,0 +1,28 @@
+// REQUIRES: swift_swift_parser
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
+
+// RUN: %target-swift-frontend -emit-module %t/Lib.swift -module-name Lib -emit-module-path %t/Lib.swiftmodule
+
+// RUN: %target-swift-frontend -typecheck -verify -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) -I %t %t/a.swift -primary-file %t/b.swift
+
+//--- Lib.swift
+
+@freestanding(expression)
+public macro magicFile() -> String = #externalMacro(module: "MacroDefinition", type: "MagicFileMacro")
+
+//--- a.swift
+
+import Lib
+
+func foo(x: String = #magicFile) {}
+
+//--- b.swift
+
+// We're missing the necessary import in this file, make sure we diagnose.
+func bar() {
+  foo() // expected-error {{no macro named 'magicFile'}}
+}