metamorphic: show op name on parsing panics

Author: RaduBerinde

metamorphic/parser.go

@@ -601,6 +601,12 @@ func (p *parser) makeOp(methodName string, receiverID, targetID objID, pos token
 			receiverID, methodName, methodName, receiverID))
 	}
 
+	defer func() {
+		if r := recover(); r != nil {
+			panic(errors.Newf("parsing %s.%s: %v", receiverID, methodName, r))
+		}
+	}()
+
 	op := info.constructor()
 	receiver, target, args := opArgs(op)
 

metamorphic/testdata/parser

@@ -16,22 +16,22 @@ metamorphic test internal error: 1:1: unknown op db1.bar
 parse
 db.Apply()
 ----
-metamorphic test internal error: 1:10: Apply: not enough arguments
+parsing db1.Apply: metamorphic test internal error: 1:10: Apply: not enough arguments
 
 parse
 db.Apply(hello)
 ----
-metamorphic test internal error: 1:10: unknown object type: "hello"
+parsing db1.Apply: metamorphic test internal error: 1:10: unknown object type: "hello"
 
 parse
 db.NewBatch()
 ----
-metamorphic test internal error: 1:1: assignment expected for db1.NewBatch
+parsing db1.NewBatch: metamorphic test internal error: 1:1: assignment expected for db1.NewBatch
 
 parse
 batch0 = db.Apply()
 ----
-metamorphic test internal error: 1:10: cannot use db1.Apply in assignment
+parsing db1.Apply: metamorphic test internal error: 1:10: cannot use db1.Apply in assignment
 
 parse
 batch0 = db.NewBatch()