Fix some compiler errors to show more information.

These were a few errors that tripped me up in my latest round
of work, where I had to add more information to figure out
what was going on.

This PR adds that missing information.

Author: jemc

main.cr

@@ -393,6 +393,9 @@ module Savi
         if check_only
           sources.each { |source_package, sources|
             ctx = Savi.compiler.compile(sources, :manifests, options)
+            errors.concat(ctx.errors)
+            next if errors.any?
+
             AST::Format.check(ctx, ctx.root_package_link, ctx.root_docs)
             errors.concat(ctx.errors)
           }
@@ -401,6 +404,9 @@ module Savi
           edited_count = 0
           sources.each { |source_package, sources|
             ctx = Savi.compiler.compile(sources, :manifests, options)
+            errors.concat(ctx.errors)
+            next if errors.any?
+
             edits_by_doc =
               AST::Format.run(ctx, ctx.root_package_link, ctx.root_docs)
 

src/savi/compiler/code_gen/continuation_info.cr

@@ -25,10 +25,13 @@ class Savi::Compiler::CodeGen
       # We don't yet support the case where the public elements of the
       # continuation data do not match - they would need to be boxed/unboxed
       # in a wrapper virtual function, which we don't yet have code for.
-      public_elements_match = concrete_infos
-        .map(&.struct_element_types.[0...3].as(Array(LLVM::Type))).uniq.one?
+      public_elements_uniq = concrete_infos
+        .map(&.struct_element_types.[0...3].as(Array(LLVM::Type))).uniq
+      public_elements_match = public_elements_uniq.one?
       raise NotImplementedError.new \
-        "heterogenous public members of virtual continuation types" \
+        "heterogenous public members of virtual continuation types: #{
+          public_elements_uniq
+        }" \
           unless public_elements_match
 
       # Create a virtual continuation struct type which has all of the