Document tuples inside containers, closes #13681

Author: josevalim

lib/elixir/pages/references/syntax-reference.md

@@ -76,7 +76,7 @@ Data structures such as lists, tuples, and binaries are marked respectively by t
 
 Maps use the `%{...}` notation and each key-value is given by pairs marked with `=>`, such as `%{"hello" => 1, 2 => "world"}`.
 
-Both keyword lists (list of two-element tuples where the first element is atom) and maps with atom keys support a keyword notation where the colon character `:` is moved to the end of the atom. `%{hello: "world"}` is equivalent to `%{:hello => "world"}` and `[foo: :bar]` is equivalent to `[{:foo, :bar}]`. This notation is a syntax sugar that emits the same AST representation. It will be explained in later sections.
+Both keyword lists (list of two-element tuples where the first element is atom) and maps with atom keys support a keyword notation where the colon character `:` is moved to the end of the atom. `%{hello: "world"}` is equivalent to `%{:hello => "world"}` and `[foo: :bar]` is equivalent to `[{:foo, :bar}]`. We discuss keywords in later sections.
 
 ### Structs
 
@@ -460,15 +460,19 @@ However, Elixir introduces a syntax sugar where the keywords above may be writte
 [foo: 1, bar: 2]
 ```
 
-Atoms with foreign characters, such as whitespace, must be wrapped in quotes. This rule applies to keywords as well:
+In order to be valid keyword syntax, `:` cannot be preceded by any whitespace (`foo : 1` is invalid) and has to be followed by whitespace (`foo:1` is invalid). Atoms with foreign characters, such as whitespace, must be wrapped in quotes. This rule applies to keywords as well:
 
 ```elixir
-[{:"foo bar", 1}, {:"bar baz", 2}] == ["foo bar": 1, "bar baz": 2]
+["foo bar": 1, "bar baz": 2] == [{:"foo bar", 1}, {:"bar baz", 2}]
 ```
 
-Remember that, because lists and two-element tuples are quoted literals, by definition keywords are also literals (in fact, the only reason tuples with two elements are quoted literals is to support keywords as literals).
+You can also mix regular list elements with keywords, but keywords must come last:
 
-In order to be valid keyword syntax, `:` cannot be preceded by any whitespace (`foo : 1` is invalid) and has to be followed by whitespace (`foo:1` is invalid).
+```elixir
+[:foo, :bar, baz: :bat] == [:foo, :bar, {:baz, :bat}]
+```
+
+Finally, because lists and two-element tuples are quoted literals, by definition keywords are also literals.
 
 ### Keywords as last arguments
 
@@ -490,6 +494,13 @@ which, as per the previous section, is the same as
 if(condition, [{:do, this}, {:else, that}])
 ```
 
+This same notation is available inside containers (such as `{...}`, `%{...}`, etc) as well:
+
+```elixir
+{:foo, :bar, baz: :bat} == {:foo, :bar, {:baz, :bat}}
+%{:foo => :bar, baz: :bat} == %{:foo => :bar, :baz => :bat}}
+```
+
 ### `do`-`end` blocks
 
 The last syntax convenience are `do`-`end` blocks. `do`-`end` blocks are equivalent to keywords as the last argument of a function call, where the block contents are wrapped in parentheses. For example:

lib/elixir/src/elixir_parser.yrl

@@ -591,13 +591,13 @@ list -> open_bracket list_args close_bracket : build_list('$1', '$2', '$3').
 % Tuple
 
 tuple -> open_curly '}' : build_tuple('$1', [], '$2').
-tuple -> open_curly kw_data '}' : bad_keyword('$1', tuple).
+tuple -> open_curly kw_data '}' : bad_keyword('$1', tuple, "'{'").
 tuple -> open_curly container_args close_curly :  build_tuple('$1', '$2', '$3').
 
 % Bitstrings
 
 bitstring -> open_bit '>>' : build_bit('$1', [], '$2').
-bitstring -> open_bit kw_data '>>' : bad_keyword('$1', bitstring).
+bitstring -> open_bit kw_data '>>' : bad_keyword('$1', bitstring, "'<<'").
 bitstring -> open_bit container_args close_bit : build_bit('$1', '$2', '$3').
 
 % Map and structs
@@ -1118,11 +1118,11 @@ error_bad_atom(Token) ->
     "If the '.' was meant to be part of the atom's name, "
     "the atom name must be quoted. Syntax error before: ", "'.'").
 
-bad_keyword(Token, Context) ->
+bad_keyword(Token, Context, StartString) ->
   return_error(?location(Token),
     "unexpected keyword list inside " ++ atom_to_list(Context) ++ ". "
     "Did you mean to write a map (using %{...}) or a list (using [...]) instead? "
-    "Syntax error after: ", "'{'").
+    "Syntax error after: ", StartString).
 
 maybe_bad_keyword_call_follow_up(_Token, KW, {'__cursor__', _, []} = Expr) ->
   reverse([Expr | KW]);