[mlir][mlir-tblgen] Emit correct error message if method is pruned (#160334)

Add verification for pruned methods for `emitCustomBuilder` and 
`emitCheckedCustomBuilder` with proper diagnostic about shadowed methods.

Without this verification, `mlir-tblgen` with `--gen-attrdef-decls`
would segmentation fault if custom builder is provided with its body,
but if method is pruned out due to duplication with other builders.

Fixes #160227 

---------

Co-authored-by: Justin Kim <[email protected]>

Author: JustinKim98

mlir/tools/mlir-tblgen/AttrOrTypeDefGen.cpp

@@ -513,14 +513,57 @@ getCustomBuilderParams(std::initializer_list<MethodParameter> prefix,
   return builderParams;
 }
 
+static std::string getSignature(const Method &m) {
+  std::string signature;
+  llvm::raw_string_ostream os(signature);
+  raw_indented_ostream indentedOs(os);
+  m.writeDeclTo(indentedOs);
+  return signature;
+}
+
+static void emitDuplicatedBuilderError(const Method &currentMethod,
+                                       StringRef methodName,
+                                       const Class &defCls,
+                                       const AttrOrTypeDef &def) {
+
+  // Try to search for method that makes `get` redundant.
+  auto loc = def.getDef()->getFieldLoc("builders");
+  for (auto &method : defCls.getMethods()) {
+    if (method->getName() == methodName &&
+        method->makesRedundant(currentMethod)) {
+      PrintError(loc, llvm::Twine("builder `") + methodName +
+                          "` conflicts with an existing builder. ");
+      PrintFatalNote(llvm::Twine("A new builder with signature:\n") +
+                     getSignature(currentMethod) +
+                     "\nis shadowed by an existing builder with signature:\n" +
+                     getSignature(*method) +
+                     "\nPlease remove one of the conflicting "
+                     "definitions.");
+    }
+  }
+
+  // This code shouldn't be reached, but leaving this here for potential future
+  // use.
+  PrintFatalError(loc, "Failed to generate builder " + methodName);
+}
+
 void DefGen::emitCustomBuilder(const AttrOrTypeBuilder &builder) {
   // Don't emit a body if there isn't one.
   auto props = builder.getBody() ? Method::Static : Method::StaticDeclaration;
   StringRef returnType = def.getCppClassName();
   if (std::optional<StringRef> builderReturnType = builder.getReturnType())
     returnType = *builderReturnType;
-  Method *m = defCls.addMethod(returnType, "get", props,
-                               getCustomBuilderParams({}, builder));
+
+  llvm::StringRef methodName = "get";
+  const auto parameters = getCustomBuilderParams({}, builder);
+  Method *m = defCls.addMethod(returnType, methodName, props, parameters);
+
+  // If method is pruned, report error and terminate.
+  if (!m) {
+    auto curMethod = Method(returnType, methodName, props, parameters);
+    emitDuplicatedBuilderError(curMethod, methodName, defCls, def);
+  }
+
   if (!builder.getBody())
     return;
 
@@ -547,11 +590,19 @@ void DefGen::emitCheckedCustomBuilder(const AttrOrTypeBuilder &builder) {
   StringRef returnType = def.getCppClassName();
   if (std::optional<StringRef> builderReturnType = builder.getReturnType())
     returnType = *builderReturnType;
-  Method *m = defCls.addMethod(
-      returnType, "getChecked", props,
-      getCustomBuilderParams(
-          {{"::llvm::function_ref<::mlir::InFlightDiagnostic()>", "emitError"}},
-          builder));
+
+  llvm::StringRef methodName = "getChecked";
+  auto parameters = getCustomBuilderParams(
+      {{"::llvm::function_ref<::mlir::InFlightDiagnostic()>", "emitError"}},
+      builder);
+  Method *m = defCls.addMethod(returnType, methodName, props, parameters);
+
+  // If method is pruned, report error and terminate.
+  if (!m) {
+    auto curMethod = Method(returnType, methodName, props, parameters);
+    emitDuplicatedBuilderError(curMethod, methodName, defCls, def);
+  }
+
   if (!builder.getBody())
     return;
 

mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp

@@ -3104,8 +3104,8 @@ void OpEmitter::genBuilder() {
     std::optional<StringRef> body = builder.getBody();
     auto properties = body ? Method::Static : Method::StaticDeclaration;
     auto *method = opClass.addMethod("void", "build", properties, arguments);
-    if (body)
-      ERROR_IF_PRUNED(method, "build", op);
+
+    ERROR_IF_PRUNED(method, "build", op);
 
     if (method)
       method->setDeprecated(builder.getDeprecatedMessage());