Do not crash when handling ambiguity errors, closes #11111

Author: josevalim

lib/elixir/src/elixir_expand.erl

@@ -1161,23 +1161,19 @@ format_error({invalid_alias, Expr}) ->
     "it at runtime. If instead you wanted to invoke a function or access a field, "
     "wrap the function or field name in double quotes",
   io_lib:format(Message, ['Elixir.Macro':to_string(Expr)]);
-format_error({op_ambiguity, Name, {Op, _, [Arg]}}) ->
+format_error({op_ambiguity, Name, Arg}) ->
   NameString = atom_to_binary(Name, utf8),
-  OpString = atom_to_binary(Op, utf8),
   ArgString = 'Elixir.Macro':to_string(Arg),
 
   Message =
-    "\"~ts ~ts~ts\" looks like a function call but there is a variable named \"~ts\".\n"
+    "\"~ts ~ts\" looks like a function call but there is a variable named \"~ts\". "
     "If you want to perform a function call, use parentheses:\n"
     "\n"
-    "    ~ts(~ts~ts)\n"
+    "    ~ts(~ts)\n"
     "\n"
-    "If you want to perform an operation on the variable ~ts, use even spaces instead:\n"
-    "\n"
-    "    ~ts ~ts ~ts",
-  io_lib:format(Message, [NameString, OpString, ArgString, NameString,
-                          NameString, OpString, ArgString, NameString,
-                          NameString, OpString, ArgString]);
+    "If you want to perform an operation on the variable ~ts, use spaces "
+    "around the unary operator",
+  io_lib:format(Message, [NameString, ArgString, NameString, NameString, ArgString, NameString]);
 format_error({invalid_clauses, Name}) ->
   Message =
     "the function \"~ts\" cannot handle clauses with the -> operator because it is not a macro. "

lib/elixir/test/elixir/kernel/expansion_test.exs

@@ -2538,10 +2538,10 @@ defmodule Kernel.ExpansionTest do
 
   describe "op ambiguity" do
     test "raises when a call is ambiguous" do
+      # We use string_to_quoted! here to avoid the formatter adding parentheses
       message = ~r["a -1" looks like a function call but there is a variable named "a"]
 
       assert_raise CompileError, message, fn ->
-        # We use string_to_quoted! here to avoid the formatter adding parentheses to "a -1".
         code =
           Code.string_to_quoted!("""
           a = 1
@@ -2550,6 +2550,18 @@ defmodule Kernel.ExpansionTest do
 
         expand(code)
       end
+
+      message = ~r["a -1..a+1" looks like a function call but there is a variable named "a"]
+
+      assert_raise CompileError, message, fn ->
+        code =
+          Code.string_to_quoted!("""
+          a = 1
+          a -1 .. a + 1
+          """)
+
+        expand(code)
+      end
     end
   end