diff --git a/mlir/test/mlir-tblgen/op-format-spec.td b/mlir/test/mlir-tblgen/op-format-spec.td
--- a/mlir/test/mlir-tblgen/op-format-spec.td
+++ b/mlir/test/mlir-tblgen/op-format-spec.td
@@ -19,7 +19,7 @@
 //===----------------------------------------------------------------------===//
 // attr-dict
 
-// CHECK: error: format missing 'attr-dict' directive
+// CHECK: error: 'attr-dict' directive not found in custom assembly format
 def DirectiveAttrDictInvalidA : TestFormat_Op<"attrdict_invalid_a", [{
 }]>;
 // CHECK: error: 'attr-dict' directive has already been seen
@@ -295,26 +295,38 @@
 // Coverage Checks
 //===----------------------------------------------------------------------===//
 
-// CHECK: error: format missing instance of result #0('result') type
+// CHECK: error: type of result #0, named 'result', is not buildable and a buildable type cannot be inferred
+// CHECK: note: suggest adding a type constraint to the operation or adding a 'type($result)' directive to the custom assembly format
 def ZCoverageInvalidA : TestFormat_Op<"variable_invalid_a", [{
   attr-dict
 }]>, Arguments<(ins AnyMemRef:$operand)>, Results<(outs AnyMemRef:$result)>;
-// CHECK: error: format missing instance of operand #0('operand')
+// CHECK: error: operand #0, named 'operand', not found in custom assembly format
+// CHECK: note: suggest adding a '$operand' directive to the custom assembly format
 def ZCoverageInvalidB : TestFormat_Op<"variable_invalid_b", [{
   type($result) attr-dict
 }]>, Arguments<(ins AnyMemRef:$operand)>, Results<(outs AnyMemRef:$result)>;
-// CHECK: error: format missing instance of operand #0('operand') type
+// CHECK: error: type of operand #0, named 'operand', is not buildable and a buildable type cannot be inferred
+// CHECK: note: suggest adding a type constraint to the operation or adding a 'type($operand)' directive to the custom assembly format
 def ZCoverageInvalidC : TestFormat_Op<"variable_invalid_c", [{
   $operand type($result) attr-dict
 }]>, Arguments<(ins AnyMemRef:$operand)>, Results<(outs AnyMemRef:$result)>;
-// CHECK: error: format missing instance of operand #0('operand') type
+// CHECK: error: type of operand #0, named 'operand', is not buildable and a buildable type cannot be inferred
+// CHECK: note: suggest adding a type constraint to the operation or adding a 'type($operand)' directive to the custom assembly format
 def ZCoverageInvalidD : TestFormat_Op<"variable_invalid_d", [{
   operands attr-dict
 }]>, Arguments<(ins Variadic<I64>:$operand)>;
-// CHECK: error: format missing instance of result #0('result') type
+// CHECK: error: type of result #0, named 'result', is not buildable and a buildable type cannot be inferred
+// CHECK: note: suggest adding a type constraint to the operation or adding a 'type($result)' directive to the custom assembly format
 def ZCoverageInvalidE : TestFormat_Op<"variable_invalid_e", [{
   attr-dict
 }]>, Results<(outs Variadic<I64>:$result)>;
+// CHECK: error: successor #0, named 'successor', not found in custom assembly format
+// CHECK: note: suggest adding a '$successor' directive to the custom assembly format
+def ZCoverageInvalidF : TestFormat_Op<"variable_invalid_f", [{
+	 attr-dict
+}]> {
+  let successors = (successor AnySuccessor:$successor);
+}
 // CHECK-NOT: error
 def ZCoverageValidA : TestFormat_Op<"variable_valid_a", [{
   $operand type($operand) type($result) attr-dict
diff --git a/mlir/tools/mlir-tblgen/OpFormatGen.cpp b/mlir/tools/mlir-tblgen/OpFormatGen.cpp
--- a/mlir/tools/mlir-tblgen/OpFormatGen.cpp
+++ b/mlir/tools/mlir-tblgen/OpFormatGen.cpp
@@ -1064,6 +1064,8 @@
   Token emitError(llvm::SMLoc loc, const Twine &msg);
   Token emitError(const char *loc, const Twine &msg);
 
+  Token emitErrorAndNote(llvm::SMLoc loc, const Twine &msg, const Twine &note);
+
 private:
   Token formToken(Token::Kind kind, const char *tokStart) {
     return Token(kind, StringRef(tokStart, curPtr - tokStart));
@@ -1092,6 +1094,12 @@
   srcMgr.PrintMessage(loc, llvm::SourceMgr::DK_Error, msg);
   return formToken(Token::error, loc.getPointer());
 }
+Token FormatLexer::emitErrorAndNote(llvm::SMLoc loc, const Twine &msg,
+                                    const Twine &note) {
+  srcMgr.PrintMessage(loc, llvm::SourceMgr::DK_Error, msg);
+  srcMgr.PrintMessage(loc, llvm::SourceMgr::DK_Note, note);
+  return formToken(Token::error, loc.getPointer());
+}
 Token FormatLexer::emitError(const char *loc, const Twine &msg) {
   return emitError(llvm::SMLoc::getFromPointer(loc), msg);
 }
@@ -1325,6 +1333,11 @@
     lexer.emitError(loc, msg);
     return failure();
   }
+  LogicalResult emitErrorAndNote(llvm::SMLoc loc, const Twine &msg,
+                                 const Twine &note) {
+    lexer.emitErrorAndNote(loc, msg, note);
+    return failure();
+  }
 
   //===--------------------------------------------------------------------===//
   // Fields
@@ -1360,7 +1373,8 @@
 
   // Check that the attribute dictionary is in the format.
   if (!hasAttrDict)
-    return emitError(loc, "format missing 'attr-dict' directive");
+    return emitError(loc, "'attr-dict' directive not found in "
+                          "custom assembly format");
 
   // Check for any type traits that we can use for inferring types.
   llvm::StringMap<TypeResolutionInstance> variableTyResolver;
@@ -1465,8 +1479,12 @@
 
     // Check that the operand itself is in the format.
     if (!hasAllOperands && !seenOperands.count(&operand)) {
-      return emitError(loc, "format missing instance of operand #" + Twine(i) +
-                                "('" + operand.name + "')");
+      return emitErrorAndNote(loc,
+                              "operand #" + Twine(i) + ", named '" +
+                                  operand.name +
+                                  "', not found in custom assembly format",
+                              "suggest adding a '$" + operand.name +
+                                  "' directive to the custom assembly format");
     }
 
     // Check that the operand type is in the format, or that it can be inferred.
@@ -1485,8 +1503,15 @@
     // we aren't using the 'operands' directive.
     Optional<StringRef> builder = operand.constraint.getBuilderCall();
     if (!builder || (hasAllOperands && operand.isVariadic())) {
-      return emitError(loc, "format missing instance of operand #" + Twine(i) +
-                                "('" + operand.name + "') type");
+      return emitErrorAndNote(
+          loc,
+          "type of operand #" + Twine(i) + ", named '" + operand.name +
+              "', is not buildable and a buildable " +
+              "type cannot be inferred",
+          "suggest adding a type constraint "
+          "to the operation or adding a "
+          "'type($" +
+              operand.name + ")' directive to the " + "custom assembly format");
     }
     auto it = buildableTypes.insert({*builder, buildableTypes.size()});
     fmt.operandTypes[i].setBuilderIdx(it.first->second);
@@ -1520,8 +1545,15 @@
     NamedTypeConstraint &result = op.getResult(i);
     Optional<StringRef> builder = result.constraint.getBuilderCall();
     if (!builder || result.constraint.isVariadic()) {
-      return emitError(loc, "format missing instance of result #" + Twine(i) +
-                                "('" + result.name + "') type");
+      return emitErrorAndNote(
+          loc,
+          "type of result #" + Twine(i) + ", named '" + result.name +
+              "', is not buildable and a buildable " +
+              "type cannot be inferred",
+          "suggest adding a type constraint "
+          "to the operation or adding a "
+          "'type($" +
+              result.name + ")' directive to the " + "custom assembly format");
     }
     // Note in the format that this result uses the custom builder.
     auto it = buildableTypes.insert({*builder, buildableTypes.size()});
@@ -1538,8 +1570,12 @@
   for (unsigned i = 0, e = op.getNumSuccessors(); i != e; ++i) {
     const NamedSuccessor &successor = op.getSuccessor(i);
     if (!seenSuccessors.count(&successor)) {
-      return emitError(loc, "format missing instance of successor #" +
-                                Twine(i) + "('" + successor.name + "')");
+      return emitErrorAndNote(loc,
+                              "successor #" + Twine(i) + ", named '" +
+                                  successor.name +
+                                  "', not found in custom assembly format",
+                              "suggest adding a '$" + successor.name +
+                                  "' directive to the custom assembly format");
     }
   }
   return success();