Refactoring the attribute plugin example to fit the new API

Make the example compile and the test case pass.

1 files changed, 33 insertions, 16 deletions

diff --git a/clang/examples/Attribute/Attribute.cpp b/clang/examples/Attribute/Attribute.cpp
index 998f175dae54..159b09e4b154 100644
--- a/clang/examples/Attribute/Attribute.cpp
+++ b/clang/examples/Attribute/Attribute.cpp
@@ -23,9 +23,10 @@ namespace {
 
 struct ExampleAttrInfo : public ParsedAttrInfo {
   ExampleAttrInfo() {
-    // Can take an optional string argument (the check that the argument
-    // actually is a string happens in handleDeclAttribute).
-    OptArgs = 1;
+    // Can take up to 15 optional arguments, to emulate accepting a variadic
+    // number of arguments. This just illustrates how many arguments a
+    // `ParsedAttrInfo` can hold, we will not use that much in this example.
+    OptArgs = 15;
     // GNU-style __attribute__(("example")) and C++-style [[example]] and
     // [[plugin::example]] supported.
     static constexpr Spelling S[] = {{ParsedAttr::AS_GNU, "example"},
@@ -39,7 +40,7 @@ struct ExampleAttrInfo : public ParsedAttrInfo {
     // This attribute appertains to functions only.
     if (!isa<FunctionDecl>(D)) {
       S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type_str)
-        << Attr << "functions";
+          << Attr << "functions";
       return false;
     }
     return true;
@@ -55,23 +56,39 @@ struct ExampleAttrInfo : public ParsedAttrInfo {
       S.Diag(Attr.getLoc(), ID);
       return AttributeNotApplied;
     }
-    // Check if we have an optional string argument.
-    StringRef Str = "";
+    // We make some rules here:
+    // 1. Only accept at most 3 arguments here.
+    // 2. The first argument must be a string literal if it exists.
+    if (Attr.getNumArgs() > 3) {
+      unsigned ID = S.getDiagnostics().getCustomDiagID(
+          DiagnosticsEngine::Error,
+          "'example' attribute only accepts at most three arguments");
+      S.Diag(Attr.getLoc(), ID);
+      return AttributeNotApplied;
+    }
+    // If there are arguments, the first argument should be a string literal.
     if (Attr.getNumArgs() > 0) {
-      Expr *ArgExpr = Attr.getArgAsExpr(0);
+      auto *Arg0 = Attr.getArgAsExpr(0);
       StringLiteral *Literal =
-          dyn_cast<StringLiteral>(ArgExpr->IgnoreParenCasts());
-      if (Literal) {
-        Str = Literal->getString();
-      } else {
-        S.Diag(ArgExpr->getExprLoc(), diag::err_attribute_argument_type)
-            << Attr.getAttrName() << AANT_ArgumentString;
+          dyn_cast<StringLiteral>(Arg0->IgnoreParenCasts());
+      if (!Literal) {
+        unsigned ID = S.getDiagnostics().getCustomDiagID(
+            DiagnosticsEngine::Error, "first argument to the 'example' "
+                                      "attribute must be a string literal");
+        S.Diag(Attr.getLoc(), ID);
         return AttributeNotApplied;
       }
+      SmallVector<Expr *, 16> ArgsBuf;
+      for (unsigned i = 0; i < Attr.getNumArgs(); i++) {
+        ArgsBuf.push_back(Attr.getArgAsExpr(i));
+      }
+      D->addAttr(AnnotateAttr::Create(S.Context, "example", ArgsBuf.data(),
+                                      ArgsBuf.size(), Attr.getRange()));
+    } else {
+      // Attach an annotate attribute to the Decl.
+      D->addAttr(AnnotateAttr::Create(S.Context, "example", nullptr, 0,
+                                      Attr.getRange()));
     }
-    // Attach an annotate attribute to the Decl.
-    D->addAttr(AnnotateAttr::Create(S.Context, "example(" + Str.str() + ")",
-                                    Attr.getRange()));
     return AttributeApplied;
   }
 };