Confusing error message when attempting to log types which can't be stored in a Metadata::Value

[dscottboggs]

Bug Report

Minimal example

playground

require "log"

Log.setup level: :trace

log = Log.for "testing"
log.error &.emit "test", does: {"this": :work?}
# symbol is not compatible              ^^^^^^

Expected behavior

An error message at compilation about the symbol :work? being incompatible with Log::Metadata::Value

Actual behavior

An undesirably vague error message at compile time

In /usr/lib/crystal/log/metadata.cr:202:27

 202 | def initialize(hash : NamedTuple | Hash)
                             ^---------
Error: can't use NamedTuple(T) in unions yet, use a more specific type

with trace

In src/test.cr:8:5

 8 | log.error &.emit "test", does: {"this": :work?}
         ^----
Error: instantiating 'Log#error()'


In src/test.cr:8:5

 8 | log.error &.emit "test", does: {"this": :work?}
         ^----
Error: instantiating 'Log#error()'


In src/test.cr:8:13

 8 | log.error &.emit "test", does: {"this": :work?}
                 ^---
Error: instantiating 'Log::Emitter#emit(String)'


In /usr/lib/crystal/log/main.cr:194:7

 194 | emit(message, kwargs)
       ^---
Error: instantiating 'emit(String, NamedTuple(does: NamedTuple(this: Symbol)))'


In /usr/lib/crystal/log/main.cr:198:55

 198 | Entry.new(@source, @severity, message, Metadata.build(data), @exception)
                                                       ^----
Error: instantiating 'Log::Metadata.class#build(NamedTuple(does: NamedTuple(this: Symbol)))'


In /usr/lib/crystal/log/metadata.cr:60:14

 60 | Metadata.new(nil, value)
               ^--
Error: instantiating 'Log::Metadata.class#new(Nil, NamedTuple(does: NamedTuple(this: Symbol)))'


In /usr/lib/crystal/log/metadata.cr:36:10

 36 | data.setup(parent, entries)
           ^----
Error: instantiating 'Log::Metadata#setup(Nil, NamedTuple(does: NamedTuple(this: Symbol)))'


In /usr/lib/crystal/log/metadata.cr:46:15

 46 | entries.each_with_index do |key, value, i|
              ^--------------
Error: instantiating 'NamedTuple(does: NamedTuple(this: Symbol))#each_with_index()'


In /usr/lib/crystal/named_tuple.cr:567:5

 567 | each do |key, value|
       ^---
Error: instantiating 'each()'


In /usr/lib/crystal/named_tuple.cr:567:5

 567 | each do |key, value|
       ^---
Error: instantiating 'each()'


In /usr/lib/crystal/log/metadata.cr:46:15

 46 | entries.each_with_index do |key, value, i|
              ^--------------
Error: instantiating 'NamedTuple(does: NamedTuple(this: Symbol))#each_with_index()'


In /usr/lib/crystal/log/metadata.cr:47:50

 47 | ptr_entries[i] = {key: key, value: Value.to_metadata_value(value)}
                                               ^----------------
Error: instantiating 'Log::Metadata::Value.class#to_metadata_value(NamedTuple(this: Symbol))'


In /usr/lib/crystal/log/metadata.cr:216:42

 216 | value.is_a?(Value) ? value : Value.new(value)
                                          ^--
Error: instantiating 'Log::Metadata::Value.class#new(NamedTuple(this: Symbol))'


In /usr/lib/crystal/log/metadata.cr:204:12

 204 | hash.each do |key, value|
            ^---
Error: instantiating 'NamedTuple(this: Symbol)#each()'


In /usr/lib/crystal/log/metadata.cr:204:12

 204 | hash.each do |key, value|
            ^---
Error: instantiating 'NamedTuple(this: Symbol)#each()'


In /usr/lib/crystal/log/metadata.cr:205:31

 205 | raw[key.to_s] = Value.to_metadata_value(value)
                             ^----------------
Error: instantiating 'Log::Metadata::Value.class#to_metadata_value(Symbol)'


In /usr/lib/crystal/log/metadata.cr:202:27

 202 | def initialize(hash : NamedTuple | Hash)
                             ^---------
Error: can't use NamedTuple(T) in unions yet, use a more specific type

Other info

Crystal version

$ crystal --version
Crystal 1.6.0 (2022-10-10)

LLVM: 14.0.6
Default target: x86_64-pc-linux-gnu

OS Version

$ uname -sor
Linux 5.19.13-arch1-1 GNU/Linux

[z64]

As a suggestion, I would be totally fine with falling back to calling #inspect on types that aren't a member of logging metadata types to simply stringify them. This is usually what I do anyways when I want to throw some data into logs without wanting to go through structuring it into metadata.