[clang] Add SuppressKeywordAttrs printing policy (PR #175398)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Kim Gräsman (kimgr)

<details>
<summary>Changes</summary>

This policy causes DeclPrinter to skip keyword attributes when printing attribute lists, for brevity.

Removing these attributes from a printed Decl post-facto is very hard (tm), especially in the presence of more complex syntax, such as template requires-expressions, alignas-expressions, default values, etc.

---
Full diff: https://github.com/llvm/llvm-project/pull/175398.diff


3 Files Affected:

- (modified) clang/include/clang/AST/PrettyPrinter.h (+6-1) 
- (modified) clang/lib/AST/DeclPrinter.cpp (+5-2) 
- (modified) clang/unittests/AST/DeclPrinterTest.cpp (+16) 


``````````diff
diff --git a/clang/include/clang/AST/PrettyPrinter.h b/clang/include/clang/AST/PrettyPrinter.h
index 2ede8da209748..a9125136bc4c3 100644
--- a/clang/include/clang/AST/PrettyPrinter.h
+++ b/clang/include/clang/AST/PrettyPrinter.h
@@ -82,7 +82,8 @@ struct PrintingPolicy {
         PrintAsCanonical(false), PrintInjectedClassNameWithArguments(true),
         UsePreferredNames(true), AlwaysIncludeTypeForTemplateArgument(false),
         CleanUglifiedParameters(false), EntireContentsOfLargeArray(true),
-        UseEnumerators(true), UseHLSLTypes(LO.HLSL) {}
+        UseEnumerators(true), UseHLSLTypes(LO.HLSL),
+        SuppressKeywordAttrs(false) {}
 
   /// Adjust this printing policy for cases where it's known that we're
   /// printing C++ code (for instance, if AST dumping reaches a C++-only
@@ -358,6 +359,10 @@ struct PrintingPolicy {
   LLVM_PREFERRED_TYPE(bool)
   unsigned UseHLSLTypes : 1;
 
+  /// Whether to suppress keyword attributes in decl printing.
+  LLVM_PREFERRED_TYPE(bool)
+  unsigned SuppressKeywordAttrs : 1;
+
   /// Callbacks to use to allow the behavior of printing to be customized.
   const PrintingCallbacks *Callbacks = nullptr;
 };
diff --git a/clang/lib/AST/DeclPrinter.cpp b/clang/lib/AST/DeclPrinter.cpp
index 205b6a53f80e5..b51d61a16f149 100644
--- a/clang/lib/AST/DeclPrinter.cpp
+++ b/clang/lib/AST/DeclPrinter.cpp
@@ -266,8 +266,11 @@ DeclPrinter::prettyPrintAttributes(const Decl *D,
   for (auto *A : D->getAttrs()) {
     if (A->isInherited() || A->isImplicit())
       continue;
-    // Print out the keyword attributes, they aren't regular attributes.
-    if (Policy.PolishForDeclaration && !A->isKeywordAttribute())
+    // Skip keyword attributes if explicitly suppressed.
+    if (A->isKeywordAttribute() && Policy.SuppressKeywordAttrs)
+      continue;
+    // PolishForDeclaration only wants keyword attributes; skip anything else.
+    if (!A->isKeywordAttribute() && Policy.PolishForDeclaration)
       continue;
     switch (A->getKind()) {
 #define ATTR(X)
diff --git a/clang/unittests/AST/DeclPrinterTest.cpp b/clang/unittests/AST/DeclPrinterTest.cpp
index a412a9813b470..82d1b89ad51e9 100644
--- a/clang/unittests/AST/DeclPrinterTest.cpp
+++ b/clang/unittests/AST/DeclPrinterTest.cpp
@@ -1572,3 +1572,19 @@ TEST(DeclPrinter, TestTemplateFinalWithPolishForDecl) {
       "template <typename T> class FinalTemplate final {}",
       [](PrintingPolicy &Policy) { Policy.PolishForDeclaration = true; }));
 }
+
+TEST(DeclPrinter, TestClassSuppressKeywordAttrs) {
+  ASSERT_TRUE(PrintedDeclCXX11Matches(
+      "class alignas(32) A final {};",
+      cxxRecordDecl(hasName("A")).bind("id"), "class A {}",
+      [](PrintingPolicy &Policy) { Policy.SuppressKeywordAttrs = true; }));
+}
+
+TEST(DeclPrinter, TestTemplateSuppressKeywordAttrs) {
+  ASSERT_TRUE(PrintedDeclCXX11Matches(
+      "template<typename T>\n"
+      "class alignas(32) A final {};",
+      classTemplateDecl(hasName("A")).bind("id"),
+      "template <typename T> class A {}",
+      [](PrintingPolicy &Policy) { Policy.SuppressKeywordAttrs = true; }));
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/175398