[mlir][Parser] Fix crash when resolving invalid operands with missing location (#128163)

When `resolveOperands` reports an error and no valid `SMLoc` was
provided, report the error at the beginning of the op instead of
crashing.

```
Assert `Ptr >= BufStart && Ptr <= Buffer->getBufferEnd()' in llvm/lib/Support/SourceMgr.cpp:llvm::SourceMgr::SrcBuffer::getLineNumberSpecialized failed
```

E.g., this is currently the case when parsing the following op with a
type but without any operands:
```
let assemblyFormat = "$str (`,` $args^)? attr-dict (`:` type($args)^)?";
```

Reported error (with this PR):
```
within split at mlir/test/IR/invalid-ops.mlir:122 offset :4:1: error: custom op 'test.variadic_args_types_split' number of operands and types do not match: got 0 operands and 1 types
test.variadic_args_types_split "hello_world" : i32
^
```

In the ODS-generated C++, the `SMLoc` is populated when parsing the
optional group containing `$args`. However, this group is missing in the
test case.

There are likely additional hand-written parsers that suffer from the
same problem.

Note: I tried emitting a second `SMLoc` for the optional type group in
the `OpFormatGen.cpp`, but this adds quite a bit of complexity in the
code base for little improvement in user experience.

Author: matthias-springer

mlir/include/mlir/IR/OpImplementation.h

@@ -1603,10 +1603,12 @@ class OpAsmParser : public AsmParser {
                   SmallVectorImpl<Value> &result) {
     size_t operandSize = llvm::range_size(operands);
     size_t typeSize = llvm::range_size(types);
-    if (operandSize != typeSize)
-      return emitError(loc)
+    if (operandSize != typeSize) {
+      // If no location was provided, report errors at the beginning of the op.
+      return emitError(loc.isValid() ? loc : getNameLoc())
              << "number of operands and types do not match: got " << operandSize
              << " operands and " << typeSize << " types";
+    }
 
     for (auto [operand, type] : llvm::zip_equal(operands, types))
       if (resolveOperand(operand, type, result))

mlir/test/IR/invalid-ops.mlir

@@ -118,3 +118,8 @@ func.func @invalid_splat(%v : f32) { // expected-note {{prior use here}}
 
 // expected-error@+1 {{expected ':' after block name}}
 "g"()({^a:^b })
+
+// -----
+
+// expected-error@+1 {{number of operands and types do not match: got 0 operands and 1 types}}
+test.variadic_args_types_split "hello_world" : i32

mlir/test/lib/Dialect/Test/TestOpsSyntax.td

@@ -767,4 +767,9 @@ def FormatInferTypeVariadicOperandsOp
   }];
 }
 
+def VariadicArgsTypesSplit : TEST_Op<"variadic_args_types_split"> {
+  let arguments = (ins StrAttr:$str, Variadic<AnyType>:$args);
+  let assemblyFormat = "$str (`,` $args^)? attr-dict (`:` type($args)^)?";
+}
+
 #endif  // TEST_OPS_SYNTAX