[Macros] Fix end location of macro declarations with where clauses

Author: DougGregor

lib/AST/Decl.cpp

@@ -9665,7 +9665,10 @@ Type MacroDecl::getResultInterfaceType() const {
 }
 
 SourceRange MacroDecl::getSourceRange() const {
-  return SourceRange(macroLoc, externalMacroTypeNameLoc);
+  SourceLoc endLoc = externalMacroTypeNameLoc;
+  if (auto trailing = getTrailingWhereClause())
+    endLoc = trailing->getSourceRange().End;
+  return SourceRange(macroLoc, endLoc);
 }
 
 SourceRange MacroExpansionDecl::getSourceRange() const {

lib/Sema/TypeCheckType.cpp

@@ -4880,6 +4880,9 @@ void TypeChecker::checkExistentialTypes(Decl *decl) {
       checkExistentialTypes(ctx, funcDecl->getGenericParams());
       checkExistentialTypes(ctx, funcDecl->getTrailingWhereClause());
     }
+  } else if (auto *macroDecl = dyn_cast<MacroDecl>(decl)) {
+    checkExistentialTypes(ctx, macroDecl->getGenericParams());
+    checkExistentialTypes(ctx, macroDecl->getTrailingWhereClause());
   }
 
   if (isa<TypeDecl>(decl) || isa<ExtensionDecl>(decl))

test/Macros/builtin_macros.swift

@@ -1,7 +1,7 @@
 // RUN: %target-swift-frontend -enable-experimental-feature Macros -enable-experimental-feature BuiltinMacros -dump-ast %s -module-name MacrosTest 2>&1 | %FileCheck %s
 // REQUIRES: OS=macosx
 
-macro function<T: ExpressibleByStringLiteral>: T = _SwiftSyntaxMacros.FunctionMacro
+macro function<T>: T = _SwiftSyntaxMacros.FunctionMacro where T: ExpressibleByStringLiteral
 macro line<T: ExpressibleByIntegerLiteral>: T = _SwiftSyntaxMacros.LineMacro
 macro column<T: ExpressibleByIntegerLiteral>: T = _SwiftSyntaxMacros.ColumnMacro
 

test/Macros/macros_diagnostics.swift

@@ -0,0 +1,9 @@
+// RUN: %target-typecheck-verify-swift -enable-experimental-feature Macros -module-name MacrosTest
+// REQUIRES: OS=macosx
+
+macro stringify<T>(_ value: T) -> (T, String) = BuiltinMacros.StringifyMacro
+
+func test(a: Int, b: Int) {
+  // FIXME: Bad diagnostic.
+  let s = #stringify<Int, Int>(a + b) // expected-error{{type of expression is ambiguous without more context}}
+}