more informative error message when a field assignment fails

teal-language · Oct 30, 2022 · eeaaa72 · eeaaa72
1 parent 8ec56f1
commit eeaaa72
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Showing 3 changed files with 25 additions and 17 deletions.
diff --git a/spec/declaration/record_method_spec.lua b/spec/declaration/record_method_spec.lua
@@ -430,7 +430,7 @@ describe("record method", function()
       function b.stop(self: Rec.Plugin)
       end
    ]], {
-      { y = 15, msg = "type signature of 'start' does not match its declaration in Rec.Plugin" }
+      { y = 15, msg = "type signature of 'start' does not match its declaration in Rec.Plugin: incompatible number of arguments: " }
    }))
 
 end)
diff --git a/tl.lua b/tl.lua
@@ -8965,23 +8965,27 @@ node.exps[3] and node.exps[3].type, }
                   filename = filename,
                })
 
-               local ok = true
-               if rtype.fields[node.name.tk] and is_a(fn_type, rtype.fields[node.name.tk]) then
-                  ok = true
-               elseif lax or owner == rtype then
+               local rfieldtype = rtype.fields[node.name.tk]
+               local ok = false
+               local err = nil
+               if rfieldtype then
+                  ok, err = is_a(fn_type, rfieldtype)
+               end
+
+               if not ok and (lax or owner == rtype) then
                   rtype.fields[node.name.tk] = fn_type
                   table.insert(rtype.field_order, node.name.tk)
                   ok = true
-               else
-                  ok = false
                end
 
                if ok then
                   node.name.type = fn_type
                else
                   local name = tl.pretty_print_ast(node.fn_owner, opts.gen_target, { preserve_indent = true, preserve_newlines = false })
-                  if rtype.fields[node.name.tk] then
-                     node_error(node, "type signature of '" .. node.name.tk .. "' does not match its declaration in " .. show_type(node.fn_owner.type))
+                  if rfieldtype then
+                     local shortname = node.fn_owner.type.typename == "nominal" and show_type(node.fn_owner.type) or name
+                     local msg = "type signature of '" .. node.name.tk .. "' does not match its declaration in " .. shortname .. ": "
+                     add_errs_prefixing(node, err, errors, msg)
                   else
                      node_error(node, "cannot add undeclared function '" .. node.name.tk .. "' outside of the scope where '" .. name .. "' was originally declared")
                   end

diff --git a/tl.tl b/tl.tl
@@ -8965,23 +8965,27 @@ tl.type_check = function(ast: Node, opts: TypeCheckOptions): Result, string
                   filename = filename,
                }
 
-               local ok = true
-               if rtype.fields[node.name.tk] and is_a(fn_type, rtype.fields[node.name.tk]) then
-                  ok = true
-               elseif lax or owner == rtype then
+               local rfieldtype = rtype.fields[node.name.tk]
+               local ok = false
+               local err: {Error} = nil
+               if rfieldtype then
+                  ok, err = is_a(fn_type, rfieldtype)
+               end
+
+               if not ok and (lax or owner == rtype) then
                   rtype.fields[node.name.tk] = fn_type
                   table.insert(rtype.field_order, node.name.tk)
                   ok = true
-               else
-                  ok = false
                end
 
                if ok then
                   node.name.type = fn_type
                else
                   local name = tl.pretty_print_ast(node.fn_owner, opts.gen_target, { preserve_indent = true, preserve_newlines = false })
-                  if rtype.fields[node.name.tk] then
-                     node_error(node, "type signature of '" .. node.name.tk .. "' does not match its declaration in " .. show_type(node.fn_owner.type))
+                  if rfieldtype then
+                     local shortname = node.fn_owner.type.typename == "nominal" and show_type(node.fn_owner.type) or name
+                     local msg = "type signature of '" .. node.name.tk .. "' does not match its declaration in " .. shortname .. ": "
+                     add_errs_prefixing(node, err, errors, msg)
                   else
                      node_error(node, "cannot add undeclared function '" .. node.name.tk .. "' outside of the scope where '" .. name .. "' was originally declared")
                   end