[mlir] do not hardcode the name of the undefined function in the error message

[ftynse]

Summary

The error message in the std.constant verifier for function-typed constants
had the name of the undefined function hardcoded to bar. Report the actual
name instead.

[silvas]

Thanks!

[stephenneuendorffer]

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

1124

nit: Generally, the first part of the message gets passed as an argument to emitOpError...

[ftynse]

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

1124

I see two occurrences of passing the first part as argument and fifteen of using repeated operator<< in this file, so I prefer (at least local) consistency.

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

if (type.isa<FunctionType>()) {
     auto fnAttr = value.dyn_cast<FlatSymbolRefAttr>();
     if (!fnAttr)
       return op.emitOpError("requires 'value' to be a function reference");
 
     // Try to find the referenced function.
     auto fn =
         op.getParentOfType<ModuleOp>().lookupSymbol<FuncOp>(fnAttr.getValue());
     if (!fn)
-      return op.emitOpError("reference to undefined function 'bar'");
+      return op.emitOpError()
+             << "reference to undefined function '" << fnAttr.getValue() << "'";
 
     // Check that the referenced function has the correct type.
     if (fn.getType() != type)
       return op.emitOpError("reference to function with mismatched type");
 
     return success();
   }
 

mlir/test/IR/invalid.mlir

^bb0:
   %x = constant @foo : (i32) -> ()  // expected-error {{reference to function with mismatched type}}
   return
 }
 
 // -----
 
 func @undefined_function() {
 ^bb0:
-  %x = constant @bar : (i32) -> ()  // expected-error {{reference to undefined function 'bar'}}
+  %x = constant @qux : (i32) -> ()  // expected-error {{reference to undefined function 'qux'}}
   return
 }
 
 // -----
 
 #map1 = affine_map<(i)[j] -> (i+j)>
 
 func @bound_symbol_mismatch(%N : index) {