[MLIR] Better message for FuncOp type mismatch

Previously the actual types were not shown, which makes the message
difficult to grok in the context of long lowering chains.  Also, it
appears that there were no actual tests for this.

Differential Revision: https://reviews.llvm.org/D88318

mlir/lib/Dialect/StandardOps/IR/Ops.cpp

@@ -758,7 +758,9 @@ static LogicalResult verify(CallOp op) {
 
   for (unsigned i = 0, e = fnType.getNumInputs(); i != e; ++i)
     if (op.getOperand(i).getType() != fnType.getInput(i))
-      return op.emitOpError("operand type mismatch");
+      return op.emitOpError("operand type mismatch: expected operand type ")
+             << fnType.getInput(i) << ", but provided "
+             << op.getOperand(i).getType() << " for operand number " << i;
 
   if (fnType.getNumResults() != op.getNumResults())
     return op.emitOpError("incorrect number of results for callee");

mlir/test/IR/operand.mlir

@@ -33,3 +33,15 @@ func @error_in_second_variadic_operand(%arg0: tensor<f32>, %arg1: f32) {
   "test.mixed_normal_variadic_operand"(%arg0, %arg0, %arg0, %arg1, %arg0) : (tensor<f32>, tensor<f32>, tensor<f32>, f32, tensor<f32>) -> ()
   return
 }
+
+// -----
+
+func @testfunc(%arg0: i32) {
+  return
+}
+func @invalid_call_operandtype() {
+  %0 = constant 0.0 : f32
+  // expected-error @+1 {{operand type mismatch: expected operand type 'i32', but provided 'f32' for operand number 0}}
+  call @testfunc(%0) : (f32) -> ()
+  return
+}