From 7e68f93ed77e0ced764af3ee009ab4d152387ef8 Mon Sep 17 00:00:00 2001
From: piegames <git@piegames.de>
Date: Sun, 14 Dec 2025 20:54:28 +0100
Subject: [PATCH] libexpr: Require whitespace between certain tokens

Fixes #135, #136

Co-authored-by: Commentator2.0 <lix@crystal-cavern.systems>
Change-Id: Ia1880633c1ee3b9242487fbc30b6d781d88987fb
---
 doc/manual/rl-next/deprecated-features.md     |  1 +
 lix/libexpr/parser/grammar.hh                 | 45 ++++++++---
 lix/libexpr/parser/parser-impl1.inc.cc        | 22 +++++
 lix/libexpr/parser/state.hh                   | 14 ++++
 .../tokens-no-whitespace.md                   | 18 +++++
 lix/libutil/meson.build                       |  1 +
 .../((0)(0))-depr.out.exp                     | 22 +++++
 .../parser-token-whitespace/((0)(0)).out.exp  | 22 +++++
 .../((a).0)-depr.err.exp                      |  4 +
 .../((a).0)-depr.out.exp                      | 21 +++++
 .../parser-token-whitespace/((a).0).err.exp   |  4 +
 .../parser-token-whitespace/((a).0).out.exp   | 21 +++++
 .../((a).a)-depr.out.exp                      | 17 ++++
 .../parser-token-whitespace/((a).a).out.exp   | 17 ++++
 .../(0.\"\")-depr.out.exp"                    | 18 +++++
 .../parser-token-whitespace/(0.\"\").err.exp" |  4 +
 .../parser-token-whitespace/(0.)-depr.err.exp |  4 +
 .../lang/parser-token-whitespace/(0.).err.exp |  4 +
 .../(0.0.0)-depr.err.exp                      |  4 +
 .../(0.0.0)-depr.out.exp                      | 22 +++++
 .../parser-token-whitespace/(0.0.0).err.exp   |  4 +
 .../(0.a)-depr.out.exp                        | 18 +++++
 .../parser-token-whitespace/(0.a).err.exp     |  4 +
 .../(00.)-depr.err.exp                        |  4 +
 .../parser-token-whitespace/(00.).err.exp     |  4 +
 .../(00012.3)-depr.err.exp                    |  4 +
 .../(00012.3)-depr.out.exp                    | 22 +++++
 .../parser-token-whitespace/(00012.3).err.exp |  4 +
 .../parser-token-whitespace/(0a)-depr.out.exp | 21 +++++
 .../lang/parser-token-whitespace/(0a).err.exp |  4 +
 .../(0https:--a)-depr.out.exp                 | 22 +++++
 .../(0https:--a).err.exp                      |  4 +
 .../(0x10)-depr.out.exp                       | 21 +++++
 .../parser-token-whitespace/(0x10).err.exp    |  4 +
 .../(1.\"\")-depr.out.exp"                    | 22 +++++
 .../parser-token-whitespace/(1.\"\").err.exp" |  4 +
 .../parser-token-whitespace/(1.)-depr.out.exp | 12 +++
 .../lang/parser-token-whitespace/(1.).out.exp | 12 +++
 .../(1.a)-depr.out.exp                        | 21 +++++
 .../parser-token-whitespace/(1.a).err.exp     |  4 +
 .../(a(\"\"))-depr.out.exp"                   | 21 +++++
 .../(a(\"\")).out.exp"                        | 21 +++++
 .../(foo\"1\"2)-depr.out.exp"                 | 26 ++++++
 .../(foo\"1\"2).err.exp"                      |  4 +
 .../[(0)(0)]-depr.out.exp                     | 22 +++++
 .../parser-token-whitespace/[(0)(0)].out.exp  | 22 +++++
 .../[(a).0]-depr.err.exp                      |  4 +
 .../[(a).0]-depr.out.exp                      | 21 +++++
 .../parser-token-whitespace/[(a).0].err.exp   |  4 +
 .../parser-token-whitespace/[(a).0].out.exp   | 21 +++++
 .../[(a).a]-depr.out.exp                      | 22 +++++
 .../parser-token-whitespace/[(a).a].out.exp   | 22 +++++
 .../[0.\"\"]-depr.out.exp"                    | 23 ++++++
 .../parser-token-whitespace/[0.\"\"].err.exp" |  4 +
 .../[0.0.0]-depr.err.exp                      |  4 +
 .../[0.0.0]-depr.out.exp                      | 22 +++++
 .../parser-token-whitespace/[0.0.0].err.exp   |  4 +
 .../parser-token-whitespace/[0.]-depr.err.exp |  4 +
 .../lang/parser-token-whitespace/[0.].err.exp |  4 +
 .../[0.a]-depr.out.exp                        | 23 ++++++
 .../parser-token-whitespace/[0.a].err.exp     |  4 +
 .../[00.]-depr.err.exp                        |  4 +
 .../parser-token-whitespace/[00.].err.exp     |  4 +
 .../[00012.3]-depr.err.exp                    |  4 +
 .../[00012.3]-depr.out.exp                    | 22 +++++
 .../parser-token-whitespace/[00012.3].err.exp |  4 +
 .../parser-token-whitespace/[0a]-depr.out.exp | 21 +++++
 .../lang/parser-token-whitespace/[0a].err.exp |  4 +
 .../[0https:--a]-depr.out.exp                 | 22 +++++
 .../[0https:--a].err.exp                      |  4 +
 .../[0x10]-depr.out.exp                       | 21 +++++
 .../parser-token-whitespace/[0x10].err.exp    |  4 +
 .../[1.\"\"]-depr.out.exp"                    | 22 +++++
 .../parser-token-whitespace/[1.\"\"].err.exp" |  4 +
 .../parser-token-whitespace/[1.]-depr.out.exp | 17 ++++
 .../lang/parser-token-whitespace/[1.].out.exp | 17 ++++
 .../[1.a]-depr.out.exp                        | 21 +++++
 .../parser-token-whitespace/[1.a].err.exp     |  4 +
 .../[a(\"\")]-depr.out.exp"                   | 21 +++++
 .../[a(\"\")].out.exp"                        | 21 +++++
 .../[foo\"1\"2]-depr.out.exp"                 | 26 ++++++
 .../[foo\"1\"2].err.exp"                      |  4 +
 .../lang/parser-token-whitespace/__init__.py  |  0
 .../test_whitespace_things.py                 | 80 +++++++++++++++++++
 tests/functional2/lang/set/test.toml          |  8 ++
 tests/nixpkgs/eval.nix                        |  1 +
 tests/nixpkgs/lib.nix                         |  1 +
 87 files changed, 1152 insertions(+), 11 deletions(-)
 create mode 100644 lix/libutil/deprecated-features/tokens-no-whitespace.md
 create mode 100644 tests/functional2/lang/parser-token-whitespace/((0)(0))-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/((0)(0)).out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/((a).0)-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/((a).0)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/((a).0).err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/((a).0).out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/((a).a)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/((a).a).out.exp
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/(0.\"\")-depr.out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/(0.\"\").err.exp"
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0.)-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0.).err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0.0.0)-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0.0.0)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0.0.0).err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0.a)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0.a).err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(00.)-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(00.).err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(00012.3)-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(00012.3)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(00012.3).err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0a)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0a).err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0https:--a)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0https:--a).err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0x10)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(0x10).err.exp
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/(1.\"\")-depr.out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/(1.\"\").err.exp"
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(1.)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(1.).out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(1.a)-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/(1.a).err.exp
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/(a(\"\"))-depr.out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/(a(\"\")).out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/(foo\"1\"2)-depr.out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/(foo\"1\"2).err.exp"
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[(0)(0)]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[(0)(0)].out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[(a).0]-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[(a).0]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[(a).0].err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[(a).0].out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[(a).a]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[(a).a].out.exp
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/[0.\"\"]-depr.out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/[0.\"\"].err.exp"
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0.0.0]-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0.0.0]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0.0.0].err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0.]-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0.].err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0.a]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0.a].err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[00.]-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[00.].err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[00012.3]-depr.err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[00012.3]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[00012.3].err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0a]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0a].err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0https:--a]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0https:--a].err.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0x10]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[0x10].err.exp
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/[1.\"\"]-depr.out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/[1.\"\"].err.exp"
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[1.]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[1.].out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[1.a]-depr.out.exp
 create mode 100644 tests/functional2/lang/parser-token-whitespace/[1.a].err.exp
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/[a(\"\")]-depr.out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/[a(\"\")].out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/[foo\"1\"2]-depr.out.exp"
 create mode 100644 "tests/functional2/lang/parser-token-whitespace/[foo\"1\"2].err.exp"
 create mode 100644 tests/functional2/lang/parser-token-whitespace/__init__.py
 create mode 100644 tests/functional2/lang/parser-token-whitespace/test_whitespace_things.py
 create mode 100644 tests/functional2/lang/set/test.toml

diff --git a/doc/manual/rl-next/deprecated-features.md b/doc/manual/rl-next/deprecated-features.md
index 0a72fc82c..b54eae104 100644
--- a/doc/manual/rl-next/deprecated-features.md
+++ b/doc/manual/rl-next/deprecated-features.md
@@ -14,3 +14,4 @@ You can opt in into the old behavior with `--extra-deprecated-features` or any e
 - `rec-set-merges` Attribute sets like `{ foo = {}; foo.bar = 42;}` implicitly merge at parse time, however if one of them is marked as recursive but not the others then the recursive attribute may get lost (order-dependent). Therefore, merging attrs with mixed-`rec` is now forbidden.
 - `rec-set-dynamic-attrs` Dynamic attributes have weird semantics in the presence of recursive attrsets (they evaluate *after* the rest of the set). This is now forbidden.
 - `or-as-identifier` `or` as an identifier has always been weird since the `or` (almost-)keyword has been introduced. We are deprecating the backcompat hacks from the early days of Nix in favor of making `or` a full and proper keyword.
+- `tokens-no-whitespace` Function applications without space around the arguments like `0a`, `0.00.0` or `foo"1"2` are now forbidden. The same applies to list elements. The primary reason for this deprecation is to remove foot guns around surprising tokenization rules regarding number literals, but this will also free up some syntax for other purposes (e.g. `r""` strings) for reuse at some point in the future.
diff --git a/lix/libexpr/parser/grammar.hh b/lix/libexpr/parser/grammar.hh
index 37959fb4f..1694fa204 100644
--- a/lix/libexpr/parser/grammar.hh
+++ b/lix/libexpr/parser/grammar.hh
@@ -12,6 +12,8 @@
 // eolf rules in favor of reproducing the old flex lexer as faithfully as
 // possible, and deferring calculation of positions to downstream users.
 
+/* clang-format absolutely butchers the template arguments */
+// clang-format off
 namespace nix::parser::grammar::v1 {
 
 using namespace tao::pegtl;
@@ -154,13 +156,20 @@ struct identifier : _not_at_any_keyword<
     star<c::id_rest>
 > {};
 
+struct _integer {
+    // Add a special case to specifically catch and forbid `0.a`, which otherwise parses as selection
+    // TODO this is only an artifact of `0.` not being a float, and should be eliminated once that is corrected
+    struct at_dot_id : success {};
+};
+
 // floats may extend ints, thus these rules are very similar.
-struct integer : seq<
+struct integer : _integer, seq<
     sor<
         seq<range<'1', '9'>, star<digit>, not_at<one<'.'>>>,
         seq<one<'0'>, not_at<one<'.'>, digit>, star<digit>>
     >,
-    not_at<_extend_as_path>
+    not_at<_extend_as_path>,
+    opt<at<seq<one<'.'>, sor<c::id_first, one<'"'>>>>, _integer::at_dot_id> // This will be not_at in the future once it becomes a hard error
 > {};
 
 struct _floating {
@@ -169,6 +178,7 @@ struct _floating {
 struct floating : _floating, seq<
     sor<
         seq<range<'1', '9'>, star<digit>, one<'.'>, star<digit>>,
+        // TODO once the deprecations don't have an opt-out anymore, parse `0.` like `1.` by using `star<digit>`
         seq<one<'0'>, one<'.'>, plus<digit>>,
         _floating::no_leading_zero
     >,
@@ -536,14 +546,26 @@ struct _expr {
         must<one<']'>>
     > {};
 
-    struct _simple : sor<
-        id,
-        int_,
-        float_,
-        string,
-        ind_string,
-        path,
-        uri,
+    struct _simple {
+        struct noseps : semantic, success {};
+        // the subset of `simple` that may not directly follow each other without whitespace as a token boundary
+        struct token_simple : sor<
+            id,
+            int_,
+            float_,
+            string,
+            ind_string,
+            path,
+            uri
+        > { };
+    };
+
+    struct simple : _simple, sor<
+        seq<
+            _simple::token_simple,
+            // error if we have <token_simple><token_simple> without whitespace in-between
+            opt<at<_simple::token_simple>, _simple::noseps>
+        >,
         seq<one<'('>, seps, must<expr>, seps, must<one<')'>>>,
         ancient_let,
         rec_set,
@@ -552,7 +574,7 @@ struct _expr {
     > {};
 
     struct _select {
-        struct head : _simple {};
+        struct head : simple {};
         struct attr : semantic, seq<attrpath> {};
         struct attr_or : semantic, must<select> {};
         struct as_app_or : semantic, t::kw_or {};
@@ -793,3 +815,4 @@ public:
     }
 };
 }
+// clang-format on
diff --git a/lix/libexpr/parser/parser-impl1.inc.cc b/lix/libexpr/parser/parser-impl1.inc.cc
index 03d272873..37c5b6910 100644
--- a/lix/libexpr/parser/parser-impl1.inc.cc
+++ b/lix/libexpr/parser/parser-impl1.inc.cc
@@ -294,6 +294,17 @@ template<> struct BuildAST<grammar::v1::formals> : change_head<FormalsState> {
     }
 };
 
+template<>
+struct BuildAST<grammar::v1::expr::simple::noseps>
+{
+    static void apply(const auto & in, auto &, State & ps)
+    {
+        if (!ps.featureSettings.isEnabled(Dep::TokensNoWhitespace)) {
+            ps.whitespaceBetweenTokensRequired(ps.at(in));
+        }
+    }
+};
+
 template<> struct BuildAST<grammar::v1::expr::lambda::arg> {
     static void apply(const auto & in, auto & s, State & ps) {
         s.pattern.name = ps.symbols.create(in.string_view());
@@ -521,6 +532,17 @@ template<> struct BuildAST<grammar::v1::expr::int_> {
     }
 };
 
+template<>
+struct BuildAST<grammar::v1::t::integer::at_dot_id>
+{
+    static void apply(const auto & in, auto &, State & ps)
+    {
+        if (!ps.featureSettings.isEnabled(Dep::TokensNoWhitespace)) {
+            ps.whitespaceBetweenTokensRequired(ps.at(in));
+        }
+    }
+};
+
 template<> struct BuildAST<grammar::v1::t::floating::no_leading_zero> {
     static void apply(const auto & in, ExprState & s, State & ps) {
         if (!ps.featureSettings.isEnabled(Dep::FloatingWithoutZero)) {
diff --git a/lix/libexpr/parser/state.hh b/lix/libexpr/parser/state.hh
index 6bed39143..2417d977b 100644
--- a/lix/libexpr/parser/state.hh
+++ b/lix/libexpr/parser/state.hh
@@ -44,6 +44,7 @@ struct State
     void recSetDynamicAttrFound(const PosIdx pos);
     void orIdentifierFound(const PosIdx pos);
     void orArgumentFound(const PosIdx pos);
+    void whitespaceBetweenTokensRequired(const PosIdx pos);
     void addAttr(ExprAttrs * attrs, AttrPath && attrPath, std::unique_ptr<Expr> e, const PosIdx pos);
     void mergeAttrs(AttrPath & attrPath, ExprSet * source, ExprSet * target);
     void validateLambdaAttrs(AttrsPattern & pattern, PosIdx pos = noPos);
@@ -228,6 +229,19 @@ inline void State::orArgumentFound(const PosIdx pos)
     });
 }
 
+// Added 2026-01-30
+inline void State::whitespaceBetweenTokensRequired(const PosIdx pos)
+{
+    throw ParseError(
+        {.msg = HintFmt(
+             "whitespace between function arguments or list elements is required here. Use %s to "
+             "disable this error",
+             "--extra-deprecated-features tokens-no-whitespace"
+         ),
+         .pos = positions[pos]}
+    );
+}
+
 inline void State::addAttr(ExprAttrs * attrs, AttrPath && attrPath, std::unique_ptr<Expr> e, const PosIdx pos)
 {
     AttrPath::iterator i;
diff --git a/lix/libutil/deprecated-features/tokens-no-whitespace.md b/lix/libutil/deprecated-features/tokens-no-whitespace.md
new file mode 100644
index 000000000..7125e9447
--- /dev/null
+++ b/lix/libutil/deprecated-features/tokens-no-whitespace.md
@@ -0,0 +1,18 @@
+---
+name: tokens-no-whitespace
+internalName: TokensNoWhitespace
+timeline:
+  - date: 2026-01-30
+    release: 2.95.0
+    cls: [4782]
+    message: Introduced as parser error.
+---
+The grammar has several bugs around token boundaries, where two adjacent literals are not always required to have whitespace between them: `0a`, `0.00.0` or `foo"1"2`.
+This results in the following unexpected behaviors in the language:
+
+- In lists, adjacent tokens will be parsed as several distinct elements, but outside of lists they will be parsed as a function application.
+- Because leading zeroes in floating point literals are not allowed, `00012.3` unexpectedly parses as `12 0.3`.
+- Nix does not have hexadecimal number literal notation, but a user naively typing `0x10` will not receive a parser error (because it validly parses as `0 x10` instead).
+
+Because the parser cannot be fixed without introducing breaking changes to the language, all token sequences with known confusing semantics are deprecated with a parse error.
+To fix this, insert whitespace between tokens to properly separate them.
diff --git a/lix/libutil/meson.build b/lix/libutil/meson.build
index 39b115c25..2690a9c05 100644
--- a/lix/libutil/meson.build
+++ b/lix/libutil/meson.build
@@ -186,6 +186,7 @@ deprecated_feature_definitions = files(
   'deprecated-features/rec-set-merges.md',
   'deprecated-features/rec-set-overrides.md',
   'deprecated-features/shadow-internal-symbols.md',
+  'deprecated-features/tokens-no-whitespace.md',
   'deprecated-features/url-literals.md',
   # keep-sorted end
 )
diff --git a/tests/functional2/lang/parser-token-whitespace/((0)(0))-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/((0)(0))-depr.out.exp
new file mode 100644
index 000000000..be9cb8d83
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/((0)(0))-depr.out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0,
+        "valueType": "Int"
+      }
+    ],
+    "fun": {
+      "_type": "ExprLiteral",
+      "value": 0,
+      "valueType": "Int"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/((0)(0)).out.exp b/tests/functional2/lang/parser-token-whitespace/((0)(0)).out.exp
new file mode 100644
index 000000000..be9cb8d83
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/((0)(0)).out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0,
+        "valueType": "Int"
+      }
+    ],
+    "fun": {
+      "_type": "ExprLiteral",
+      "value": 0,
+      "valueType": "Int"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/((a).0)-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/((a).0)-depr.err.exp
new file mode 100644
index 000000000..702253687
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/((a).0)-depr.err.exp
@@ -0,0 +1,4 @@
+warning: Found floating point literal without leading zero. To fix this warning, add a zero before the dot. Use --extra-deprecated-feature floating-without-zero to silence this warning
+         at «string»:1:14:
+              1| with {}; ((a).0)
+               |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/((a).0)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/((a).0)-depr.out.exp
new file mode 100644
index 000000000..50cc59099
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/((a).0)-depr.out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0.0,
+        "valueType": "Float"
+      }
+    ],
+    "fun": {
+      "_type": "ExprVar",
+      "value": "a"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/((a).0).err.exp b/tests/functional2/lang/parser-token-whitespace/((a).0).err.exp
new file mode 100644
index 000000000..702253687
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/((a).0).err.exp
@@ -0,0 +1,4 @@
+warning: Found floating point literal without leading zero. To fix this warning, add a zero before the dot. Use --extra-deprecated-feature floating-without-zero to silence this warning
+         at «string»:1:14:
+              1| with {}; ((a).0)
+               |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/((a).0).out.exp b/tests/functional2/lang/parser-token-whitespace/((a).0).out.exp
new file mode 100644
index 000000000..50cc59099
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/((a).0).out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0.0,
+        "valueType": "Float"
+      }
+    ],
+    "fun": {
+      "_type": "ExprVar",
+      "value": "a"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/((a).a)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/((a).a)-depr.out.exp
new file mode 100644
index 000000000..590d80aa5
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/((a).a)-depr.out.exp
@@ -0,0 +1,17 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprSelect",
+    "attrs": [
+      "a"
+    ],
+    "e": {
+      "_type": "ExprVar",
+      "value": "a"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/((a).a).out.exp b/tests/functional2/lang/parser-token-whitespace/((a).a).out.exp
new file mode 100644
index 000000000..590d80aa5
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/((a).a).out.exp
@@ -0,0 +1,17 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprSelect",
+    "attrs": [
+      "a"
+    ],
+    "e": {
+      "_type": "ExprVar",
+      "value": "a"
+    }
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/(0.\"\")-depr.out.exp" "b/tests/functional2/lang/parser-token-whitespace/(0.\"\")-depr.out.exp"
new file mode 100644
index 000000000..542c21066
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/(0.\"\")-depr.out.exp"
@@ -0,0 +1,18 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprSelect",
+    "attrs": [
+      ""
+    ],
+    "e": {
+      "_type": "ExprLiteral",
+      "value": 0,
+      "valueType": "Int"
+    }
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/(0.\"\").err.exp" "b/tests/functional2/lang/parser-token-whitespace/(0.\"\").err.exp"
new file mode 100644
index 000000000..3ebca1991
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/(0.\"\").err.exp"
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; (0."")
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(0.)-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/(0.)-depr.err.exp
new file mode 100644
index 000000000..9d6ff7eff
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0.)-depr.err.exp
@@ -0,0 +1,4 @@
+error: syntax error, expecting ')'
+       at «string»:1:12:
+            1| with {}; (0.)
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(0.).err.exp b/tests/functional2/lang/parser-token-whitespace/(0.).err.exp
new file mode 100644
index 000000000..9d6ff7eff
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0.).err.exp
@@ -0,0 +1,4 @@
+error: syntax error, expecting ')'
+       at «string»:1:12:
+            1| with {}; (0.)
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(0.0.0)-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/(0.0.0)-depr.err.exp
new file mode 100644
index 000000000..90e2480ba
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0.0.0)-depr.err.exp
@@ -0,0 +1,4 @@
+warning: Found floating point literal without leading zero. To fix this warning, add a zero before the dot. Use --extra-deprecated-feature floating-without-zero to silence this warning
+         at «string»:1:14:
+              1| with {}; (0.0.0)
+               |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(0.0.0)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/(0.0.0)-depr.out.exp
new file mode 100644
index 000000000..84a0d4466
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0.0.0)-depr.out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0.0,
+        "valueType": "Float"
+      }
+    ],
+    "fun": {
+      "_type": "ExprLiteral",
+      "value": 0.0,
+      "valueType": "Float"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/(0.0.0).err.exp b/tests/functional2/lang/parser-token-whitespace/(0.0.0).err.exp
new file mode 100644
index 000000000..fb63f1b19
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0.0.0).err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:14:
+            1| with {}; (0.0.0)
+             |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(0.a)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/(0.a)-depr.out.exp
new file mode 100644
index 000000000..88325748e
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0.a)-depr.out.exp
@@ -0,0 +1,18 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprSelect",
+    "attrs": [
+      "a"
+    ],
+    "e": {
+      "_type": "ExprLiteral",
+      "value": 0,
+      "valueType": "Int"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/(0.a).err.exp b/tests/functional2/lang/parser-token-whitespace/(0.a).err.exp
new file mode 100644
index 000000000..ff70d444e
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0.a).err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; (0.a)
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(00.)-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/(00.)-depr.err.exp
new file mode 100644
index 000000000..daa1faa65
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(00.)-depr.err.exp
@@ -0,0 +1,4 @@
+error: syntax error, expecting ')'
+       at «string»:1:13:
+            1| with {}; (00.)
+             |             ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(00.).err.exp b/tests/functional2/lang/parser-token-whitespace/(00.).err.exp
new file mode 100644
index 000000000..daa1faa65
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(00.).err.exp
@@ -0,0 +1,4 @@
+error: syntax error, expecting ')'
+       at «string»:1:13:
+            1| with {}; (00.)
+             |             ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(00012.3)-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/(00012.3)-depr.err.exp
new file mode 100644
index 000000000..9b59a6f2b
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(00012.3)-depr.err.exp
@@ -0,0 +1,4 @@
+warning: Found floating point literal without leading zero. To fix this warning, add a zero before the dot. Use --extra-deprecated-feature floating-without-zero to silence this warning
+         at «string»:1:16:
+              1| with {}; (00012.3)
+               |                ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(00012.3)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/(00012.3)-depr.out.exp
new file mode 100644
index 000000000..fa0de0e0c
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(00012.3)-depr.out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0.3,
+        "valueType": "Float"
+      }
+    ],
+    "fun": {
+      "_type": "ExprLiteral",
+      "value": 12,
+      "valueType": "Int"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/(00012.3).err.exp b/tests/functional2/lang/parser-token-whitespace/(00012.3).err.exp
new file mode 100644
index 000000000..3b5550aac
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(00012.3).err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:16:
+            1| with {}; (00012.3)
+             |                ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(0a)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/(0a)-depr.out.exp
new file mode 100644
index 000000000..7e04537b1
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0a)-depr.out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprVar",
+        "value": "a"
+      }
+    ],
+    "fun": {
+      "_type": "ExprLiteral",
+      "value": 0,
+      "valueType": "Int"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/(0a).err.exp b/tests/functional2/lang/parser-token-whitespace/(0a).err.exp
new file mode 100644
index 000000000..3ffa5b395
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0a).err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; (0a)
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(0https:--a)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/(0https:--a)-depr.out.exp
new file mode 100644
index 000000000..c70f8f69b
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0https:--a)-depr.out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": "https://a",
+        "valueType": "String"
+      }
+    ],
+    "fun": {
+      "_type": "ExprLiteral",
+      "value": 0,
+      "valueType": "Int"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/(0https:--a).err.exp b/tests/functional2/lang/parser-token-whitespace/(0https:--a).err.exp
new file mode 100644
index 000000000..2ade5dce0
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0https:--a).err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; (0https://a)
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(0x10)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/(0x10)-depr.out.exp
new file mode 100644
index 000000000..7a788cb23
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0x10)-depr.out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprVar",
+        "value": "x10"
+      }
+    ],
+    "fun": {
+      "_type": "ExprLiteral",
+      "value": 0,
+      "valueType": "Int"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/(0x10).err.exp b/tests/functional2/lang/parser-token-whitespace/(0x10).err.exp
new file mode 100644
index 000000000..d0eddd764
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(0x10).err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; (0x10)
+             |            ^
diff --git "a/tests/functional2/lang/parser-token-whitespace/(1.\"\")-depr.out.exp" "b/tests/functional2/lang/parser-token-whitespace/(1.\"\")-depr.out.exp"
new file mode 100644
index 000000000..536970d44
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/(1.\"\")-depr.out.exp"
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": "",
+        "valueType": "String"
+      }
+    ],
+    "fun": {
+      "_type": "ExprLiteral",
+      "value": 1.0,
+      "valueType": "Float"
+    }
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/(1.\"\").err.exp" "b/tests/functional2/lang/parser-token-whitespace/(1.\"\").err.exp"
new file mode 100644
index 000000000..7f7dc79d5
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/(1.\"\").err.exp"
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:13:
+            1| with {}; (1."")
+             |             ^
diff --git a/tests/functional2/lang/parser-token-whitespace/(1.)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/(1.)-depr.out.exp
new file mode 100644
index 000000000..034973942
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(1.)-depr.out.exp
@@ -0,0 +1,12 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprLiteral",
+    "value": 1.0,
+    "valueType": "Float"
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/(1.).out.exp b/tests/functional2/lang/parser-token-whitespace/(1.).out.exp
new file mode 100644
index 000000000..034973942
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(1.).out.exp
@@ -0,0 +1,12 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprLiteral",
+    "value": 1.0,
+    "valueType": "Float"
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/(1.a)-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/(1.a)-depr.out.exp
new file mode 100644
index 000000000..67c27eba1
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(1.a)-depr.out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprVar",
+        "value": "a"
+      }
+    ],
+    "fun": {
+      "_type": "ExprLiteral",
+      "value": 1.0,
+      "valueType": "Float"
+    }
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/(1.a).err.exp b/tests/functional2/lang/parser-token-whitespace/(1.a).err.exp
new file mode 100644
index 000000000..10bdb96b9
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/(1.a).err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:13:
+            1| with {}; (1.a)
+             |             ^
diff --git "a/tests/functional2/lang/parser-token-whitespace/(a(\"\"))-depr.out.exp" "b/tests/functional2/lang/parser-token-whitespace/(a(\"\"))-depr.out.exp"
new file mode 100644
index 000000000..c75687077
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/(a(\"\"))-depr.out.exp"
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": "",
+        "valueType": "String"
+      }
+    ],
+    "fun": {
+      "_type": "ExprVar",
+      "value": "a"
+    }
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/(a(\"\")).out.exp" "b/tests/functional2/lang/parser-token-whitespace/(a(\"\")).out.exp"
new file mode 100644
index 000000000..c75687077
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/(a(\"\")).out.exp"
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": "",
+        "valueType": "String"
+      }
+    ],
+    "fun": {
+      "_type": "ExprVar",
+      "value": "a"
+    }
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/(foo\"1\"2)-depr.out.exp" "b/tests/functional2/lang/parser-token-whitespace/(foo\"1\"2)-depr.out.exp"
new file mode 100644
index 000000000..3668216cd
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/(foo\"1\"2)-depr.out.exp"
@@ -0,0 +1,26 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprCall",
+    "args": [
+      {
+        "_type": "ExprLiteral",
+        "value": "1",
+        "valueType": "String"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": 2,
+        "valueType": "Int"
+      }
+    ],
+    "fun": {
+      "_type": "ExprVar",
+      "value": "foo"
+    }
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/(foo\"1\"2).err.exp" "b/tests/functional2/lang/parser-token-whitespace/(foo\"1\"2).err.exp"
new file mode 100644
index 000000000..85bf3b480
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/(foo\"1\"2).err.exp"
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:14:
+            1| with {}; (foo"1"2)
+             |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[(0)(0)]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[(0)(0)]-depr.out.exp
new file mode 100644
index 000000000..104fbe285
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[(0)(0)]-depr.out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0,
+        "valueType": "Int"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": 0,
+        "valueType": "Int"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[(0)(0)].out.exp b/tests/functional2/lang/parser-token-whitespace/[(0)(0)].out.exp
new file mode 100644
index 000000000..104fbe285
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[(0)(0)].out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0,
+        "valueType": "Int"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": 0,
+        "valueType": "Int"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[(a).0]-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/[(a).0]-depr.err.exp
new file mode 100644
index 000000000..6caca6f81
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[(a).0]-depr.err.exp
@@ -0,0 +1,4 @@
+warning: Found floating point literal without leading zero. To fix this warning, add a zero before the dot. Use --extra-deprecated-feature floating-without-zero to silence this warning
+         at «string»:1:14:
+              1| with {}; [(a).0]
+               |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[(a).0]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[(a).0]-depr.out.exp
new file mode 100644
index 000000000..ae5b9f69b
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[(a).0]-depr.out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprVar",
+        "value": "a"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": 0.0,
+        "valueType": "Float"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[(a).0].err.exp b/tests/functional2/lang/parser-token-whitespace/[(a).0].err.exp
new file mode 100644
index 000000000..6caca6f81
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[(a).0].err.exp
@@ -0,0 +1,4 @@
+warning: Found floating point literal without leading zero. To fix this warning, add a zero before the dot. Use --extra-deprecated-feature floating-without-zero to silence this warning
+         at «string»:1:14:
+              1| with {}; [(a).0]
+               |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[(a).0].out.exp b/tests/functional2/lang/parser-token-whitespace/[(a).0].out.exp
new file mode 100644
index 000000000..ae5b9f69b
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[(a).0].out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprVar",
+        "value": "a"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": 0.0,
+        "valueType": "Float"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[(a).a]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[(a).a]-depr.out.exp
new file mode 100644
index 000000000..cb95d6d5c
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[(a).a]-depr.out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprSelect",
+        "attrs": [
+          "a"
+        ],
+        "e": {
+          "_type": "ExprVar",
+          "value": "a"
+        }
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[(a).a].out.exp b/tests/functional2/lang/parser-token-whitespace/[(a).a].out.exp
new file mode 100644
index 000000000..cb95d6d5c
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[(a).a].out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprSelect",
+        "attrs": [
+          "a"
+        ],
+        "e": {
+          "_type": "ExprVar",
+          "value": "a"
+        }
+      }
+    ]
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/[0.\"\"]-depr.out.exp" "b/tests/functional2/lang/parser-token-whitespace/[0.\"\"]-depr.out.exp"
new file mode 100644
index 000000000..49856fc44
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/[0.\"\"]-depr.out.exp"
@@ -0,0 +1,23 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprSelect",
+        "attrs": [
+          ""
+        ],
+        "e": {
+          "_type": "ExprLiteral",
+          "value": 0,
+          "valueType": "Int"
+        }
+      }
+    ]
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/[0.\"\"].err.exp" "b/tests/functional2/lang/parser-token-whitespace/[0.\"\"].err.exp"
new file mode 100644
index 000000000..4be65156b
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/[0.\"\"].err.exp"
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; [0.""]
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[0.0.0]-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/[0.0.0]-depr.err.exp
new file mode 100644
index 000000000..7d481f12b
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0.0.0]-depr.err.exp
@@ -0,0 +1,4 @@
+warning: Found floating point literal without leading zero. To fix this warning, add a zero before the dot. Use --extra-deprecated-feature floating-without-zero to silence this warning
+         at «string»:1:14:
+              1| with {}; [0.0.0]
+               |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[0.0.0]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[0.0.0]-depr.out.exp
new file mode 100644
index 000000000..80819338a
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0.0.0]-depr.out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0.0,
+        "valueType": "Float"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": 0.0,
+        "valueType": "Float"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[0.0.0].err.exp b/tests/functional2/lang/parser-token-whitespace/[0.0.0].err.exp
new file mode 100644
index 000000000..4eed485e6
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0.0.0].err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:14:
+            1| with {}; [0.0.0]
+             |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[0.]-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/[0.]-depr.err.exp
new file mode 100644
index 000000000..3c00b49b4
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0.]-depr.err.exp
@@ -0,0 +1,4 @@
+error: syntax error, expecting ']'
+       at «string»:1:12:
+            1| with {}; [0.]
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[0.].err.exp b/tests/functional2/lang/parser-token-whitespace/[0.].err.exp
new file mode 100644
index 000000000..3c00b49b4
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0.].err.exp
@@ -0,0 +1,4 @@
+error: syntax error, expecting ']'
+       at «string»:1:12:
+            1| with {}; [0.]
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[0.a]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[0.a]-depr.out.exp
new file mode 100644
index 000000000..4a4f1260c
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0.a]-depr.out.exp
@@ -0,0 +1,23 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprSelect",
+        "attrs": [
+          "a"
+        ],
+        "e": {
+          "_type": "ExprLiteral",
+          "value": 0,
+          "valueType": "Int"
+        }
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[0.a].err.exp b/tests/functional2/lang/parser-token-whitespace/[0.a].err.exp
new file mode 100644
index 000000000..70ed7f79c
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0.a].err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; [0.a]
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[00.]-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/[00.]-depr.err.exp
new file mode 100644
index 000000000..74c68c9a3
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[00.]-depr.err.exp
@@ -0,0 +1,4 @@
+error: syntax error, expecting ']'
+       at «string»:1:13:
+            1| with {}; [00.]
+             |             ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[00.].err.exp b/tests/functional2/lang/parser-token-whitespace/[00.].err.exp
new file mode 100644
index 000000000..74c68c9a3
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[00.].err.exp
@@ -0,0 +1,4 @@
+error: syntax error, expecting ']'
+       at «string»:1:13:
+            1| with {}; [00.]
+             |             ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[00012.3]-depr.err.exp b/tests/functional2/lang/parser-token-whitespace/[00012.3]-depr.err.exp
new file mode 100644
index 000000000..64ffd836f
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[00012.3]-depr.err.exp
@@ -0,0 +1,4 @@
+warning: Found floating point literal without leading zero. To fix this warning, add a zero before the dot. Use --extra-deprecated-feature floating-without-zero to silence this warning
+         at «string»:1:16:
+              1| with {}; [00012.3]
+               |                ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[00012.3]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[00012.3]-depr.out.exp
new file mode 100644
index 000000000..1d32fba03
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[00012.3]-depr.out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 12,
+        "valueType": "Int"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": 0.3,
+        "valueType": "Float"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[00012.3].err.exp b/tests/functional2/lang/parser-token-whitespace/[00012.3].err.exp
new file mode 100644
index 000000000..19ce2f6dc
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[00012.3].err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:16:
+            1| with {}; [00012.3]
+             |                ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[0a]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[0a]-depr.out.exp
new file mode 100644
index 000000000..d798aba62
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0a]-depr.out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0,
+        "valueType": "Int"
+      },
+      {
+        "_type": "ExprVar",
+        "value": "a"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[0a].err.exp b/tests/functional2/lang/parser-token-whitespace/[0a].err.exp
new file mode 100644
index 000000000..c555bd1cd
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0a].err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; [0a]
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[0https:--a]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[0https:--a]-depr.out.exp
new file mode 100644
index 000000000..e99c24c02
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0https:--a]-depr.out.exp
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0,
+        "valueType": "Int"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": "https://a",
+        "valueType": "String"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[0https:--a].err.exp b/tests/functional2/lang/parser-token-whitespace/[0https:--a].err.exp
new file mode 100644
index 000000000..712aae7f0
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0https:--a].err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; [0https://a]
+             |            ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[0x10]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[0x10]-depr.out.exp
new file mode 100644
index 000000000..c24306715
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0x10]-depr.out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 0,
+        "valueType": "Int"
+      },
+      {
+        "_type": "ExprVar",
+        "value": "x10"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[0x10].err.exp b/tests/functional2/lang/parser-token-whitespace/[0x10].err.exp
new file mode 100644
index 000000000..14f88fb1a
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[0x10].err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:12:
+            1| with {}; [0x10]
+             |            ^
diff --git "a/tests/functional2/lang/parser-token-whitespace/[1.\"\"]-depr.out.exp" "b/tests/functional2/lang/parser-token-whitespace/[1.\"\"]-depr.out.exp"
new file mode 100644
index 000000000..92c71fef8
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/[1.\"\"]-depr.out.exp"
@@ -0,0 +1,22 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 1.0,
+        "valueType": "Float"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": "",
+        "valueType": "String"
+      }
+    ]
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/[1.\"\"].err.exp" "b/tests/functional2/lang/parser-token-whitespace/[1.\"\"].err.exp"
new file mode 100644
index 000000000..23baef7db
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/[1.\"\"].err.exp"
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:13:
+            1| with {}; [1.""]
+             |             ^
diff --git a/tests/functional2/lang/parser-token-whitespace/[1.]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[1.]-depr.out.exp
new file mode 100644
index 000000000..3635f36f8
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[1.]-depr.out.exp
@@ -0,0 +1,17 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 1.0,
+        "valueType": "Float"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[1.].out.exp b/tests/functional2/lang/parser-token-whitespace/[1.].out.exp
new file mode 100644
index 000000000..3635f36f8
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[1.].out.exp
@@ -0,0 +1,17 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 1.0,
+        "valueType": "Float"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[1.a]-depr.out.exp b/tests/functional2/lang/parser-token-whitespace/[1.a]-depr.out.exp
new file mode 100644
index 000000000..650dcf137
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[1.a]-depr.out.exp
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprLiteral",
+        "value": 1.0,
+        "valueType": "Float"
+      },
+      {
+        "_type": "ExprVar",
+        "value": "a"
+      }
+    ]
+  }
+}
diff --git a/tests/functional2/lang/parser-token-whitespace/[1.a].err.exp b/tests/functional2/lang/parser-token-whitespace/[1.a].err.exp
new file mode 100644
index 000000000..ebf5524a9
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/[1.a].err.exp
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:13:
+            1| with {}; [1.a]
+             |             ^
diff --git "a/tests/functional2/lang/parser-token-whitespace/[a(\"\")]-depr.out.exp" "b/tests/functional2/lang/parser-token-whitespace/[a(\"\")]-depr.out.exp"
new file mode 100644
index 000000000..04605181e
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/[a(\"\")]-depr.out.exp"
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprVar",
+        "value": "a"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": "",
+        "valueType": "String"
+      }
+    ]
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/[a(\"\")].out.exp" "b/tests/functional2/lang/parser-token-whitespace/[a(\"\")].out.exp"
new file mode 100644
index 000000000..04605181e
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/[a(\"\")].out.exp"
@@ -0,0 +1,21 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprVar",
+        "value": "a"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": "",
+        "valueType": "String"
+      }
+    ]
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/[foo\"1\"2]-depr.out.exp" "b/tests/functional2/lang/parser-token-whitespace/[foo\"1\"2]-depr.out.exp"
new file mode 100644
index 000000000..7135822e9
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/[foo\"1\"2]-depr.out.exp"
@@ -0,0 +1,26 @@
+{
+  "_type": "ExprWith",
+  "attrs": {
+    "_type": "ExprSet",
+    "recursive": false
+  },
+  "body": {
+    "_type": "ExprList",
+    "elems": [
+      {
+        "_type": "ExprVar",
+        "value": "foo"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": "1",
+        "valueType": "String"
+      },
+      {
+        "_type": "ExprLiteral",
+        "value": 2,
+        "valueType": "Int"
+      }
+    ]
+  }
+}
diff --git "a/tests/functional2/lang/parser-token-whitespace/[foo\"1\"2].err.exp" "b/tests/functional2/lang/parser-token-whitespace/[foo\"1\"2].err.exp"
new file mode 100644
index 000000000..c2a2a47cd
--- /dev/null
+++ "b/tests/functional2/lang/parser-token-whitespace/[foo\"1\"2].err.exp"
@@ -0,0 +1,4 @@
+error: whitespace between function arguments or list elements is required here. Use --extra-deprecated-features tokens-no-whitespace to disable this error
+       at «string»:1:14:
+            1| with {}; [foo"1"2]
+             |              ^
diff --git a/tests/functional2/lang/parser-token-whitespace/__init__.py b/tests/functional2/lang/parser-token-whitespace/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/functional2/lang/parser-token-whitespace/test_whitespace_things.py b/tests/functional2/lang/parser-token-whitespace/test_whitespace_things.py
new file mode 100644
index 000000000..2185532a7
--- /dev/null
+++ b/tests/functional2/lang/parser-token-whitespace/test_whitespace_things.py
@@ -0,0 +1,80 @@
+from pathlib import Path
+from collections.abc import Callable
+
+import pytest
+
+from testlib.fixtures.nix import Nix
+from testlib.fixtures.snapshot import Snapshot
+from testlib.utils import functional2_base_folder
+
+
+@pytest.mark.parametrize(
+    ("expr", "exit_code", "exit_code_depr"),
+    [
+        ("00012.3", 1, 0),
+        ("0a", 1, 0),
+        ("0https://a", 1, 0),
+        ("0.0.0", 1, 0),
+        ("""foo"1"2""", 1, 0),
+        ("0x10", 1, 0),
+        ("0.", 1, 1),
+        ("1.", 0, 0),
+        ("0.a", 1, 0),
+        ("1.a", 1, 0),
+        (""" 0."" """, 1, 0),
+        (""" 1."" """, 1, 0),
+        # test against false positives
+        ("(0)(0)", 0, 0),
+        ('a("")', 0, 0),
+        ("(a).a", 0, 0),
+        # not deprecated atm but probably should be in the future (FIXME piegames; 2026-01-30)
+        ("(a).0", 0, 0),
+        # unrelated syntax errors which don't trigger the deprecation
+        ("00.", 1, 1),
+    ],
+)
+def test_whitespace(
+    nix: Nix,
+    expr: str,
+    exit_code: int,
+    exit_code_depr: int,
+    snapshot: Callable[[str], Snapshot],
+    files: Path,
+):
+    expr = expr.strip()
+    for i, expr in enumerate((f"({expr})", f"[{expr}]")):
+        f_expr = expr.replace("/", "-")
+        for f in [
+            f"{f_expr}.out.exp",
+            f"{f_expr}.err.exp",
+            f"{f_expr}-depr.out.exp",
+            f"{f_expr}-depr.err.exp",
+        ]:
+            (files / f).symlink_to(functional2_base_folder / "lang" / "parser-token-whitespace" / f)
+
+        full_expr = f"with {{}}; {expr}"
+        res = (
+            nix.nix_instantiate(
+                ["--parse", "--extra-deprecated-features", "url-literals", "-E", full_expr]
+            )
+            .run()
+            .expect(exit_code)
+        )
+        assert snapshot(f"{f_expr}.out.exp") == res.stdout_s
+        assert snapshot(f"{f_expr}.err.exp") == res.stderr_s
+
+        res = (
+            nix.nix_instantiate(
+                [
+                    "--parse",
+                    "--extra-deprecated-features",
+                    "tokens-no-whitespace url-literals",
+                    "-E",
+                    full_expr,
+                ]
+            )
+            .run()
+            .expect(exit_code_depr)
+        )
+        assert snapshot(f"{f_expr}-depr.out.exp") == res.stdout_s
+        assert snapshot(f"{f_expr}-depr.err.exp") == res.stderr_s
diff --git a/tests/functional2/lang/set/test.toml b/tests/functional2/lang/set/test.toml
new file mode 100644
index 000000000..7b52fec9f
--- /dev/null
+++ b/tests/functional2/lang/set/test.toml
@@ -0,0 +1,8 @@
+[[test]]
+runner = "parse-fail"
+in = "in.nix"
+flags = ["--extra-deprecated-features", "tokens-no-whitespace"]
+
+[[test]]
+runner = "eval-fail"
+in = "in-2.nix"
diff --git a/tests/nixpkgs/eval.nix b/tests/nixpkgs/eval.nix
index 404cfa0a3..b94cf4e55 100644
--- a/tests/nixpkgs/eval.nix
+++ b/tests/nixpkgs/eval.nix
@@ -16,6 +16,7 @@ let
     "rec-set-merges"
     "rec-set-dynamic-attrs"
     "or-as-identifier"
+    "tokens-no-whitespace"
   ];
 in
 
diff --git a/tests/nixpkgs/lib.nix b/tests/nixpkgs/lib.nix
index 1f328e105..d73f97586 100644
--- a/tests/nixpkgs/lib.nix
+++ b/tests/nixpkgs/lib.nix
@@ -25,6 +25,7 @@ let
     "rec-set-merges"
     "rec-set-dynamic-attrs"
     "or-as-identifier"
+    "tokens-no-whitespace"
   ];
 
   env.NIX_CONFIG = "extra-deprecated-features = ${concatStringsSep " " deprecatedFeatures}";