From 5c0cec2d29a0580a8e171e040f13427b282c4c1f Mon Sep 17 00:00:00 2001
From: Markus Westerlind <marwes91@gmail.com>
Date: Sun, 20 Sep 2020 01:00:30 +0200
Subject: [PATCH] feat: Format seq expressions without seq

---
 Cargo.lock                       | 11 +++++++++++
 book/src/syntax-and-semantics.md | 13 +++++++++++--
 format/Cargo.toml                |  1 +
 format/src/pretty_print.rs       | 27 ++++++++++++++++-----------
 format/tests/pretty_print.rs     | 25 ++++++++++++++++++++++++-
 std/parser.glu                   |  2 +-
 6 files changed, 64 insertions(+), 15 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 280ea251af..de077e7601 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -810,6 +810,16 @@ dependencies = [
  "version_check",
 ]
 
+[[package]]
+name = "expect-test"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ceb96f3eaa0d4e8769c52dacfd4eb60183b817ed2f176171b3c691d5022b0f2e"
+dependencies = [
+ "difference",
+ "once_cell",
+]
+
 [[package]]
 name = "failure"
 version = "0.1.8"
@@ -1292,6 +1302,7 @@ dependencies = [
  "codespan",
  "difference",
  "env_logger 0.7.1",
+ "expect-test",
  "futures 0.3.5",
  "gluon",
  "gluon_base",
diff --git a/book/src/syntax-and-semantics.md b/book/src/syntax-and-semantics.md
index 12ff816c4d..a2a60ee7c3 100644
--- a/book/src/syntax-and-semantics.md
+++ b/book/src/syntax-and-semantics.md
@@ -334,9 +334,18 @@ do { y } = Some { y = "" }
 Some y
 ```
 
-### Seq expressions
+### Sequence expressions
 
-`seq` expressions work just like `do` expressions, only they do not have a binding.
+Sequence expressions work just like `do` expressions, only they do not have a binding.
+
+```f#,rust
+let io @ { ? } = import! std.io
+io.print "Hello"
+io.print " "
+io.println "world!"
+```
+
+For backwards compatibility it is also possible to write (`seq`) before each expression.
 
 ```f#,rust
 let io @ { ? } = import! std.io
diff --git a/format/Cargo.toml b/format/Cargo.toml
index f9b5e2e89a..cc3a8d7e69 100644
--- a/format/Cargo.toml
+++ b/format/Cargo.toml
@@ -22,6 +22,7 @@ gluon_base = { path = "../base", version = "0.17.1" } # GLUON
 [dev-dependencies]
 difference = "2"
 env_logger = "0.7"
+expect-test = "1"
 futures = "0.3.1"
 pretty_assertions = "0.6"
 tokio = { version = "0.2", features = ["macros", "rt-core"] }
diff --git a/format/src/pretty_print.rs b/format/src/pretty_print.rs
index a9e4349e54..e76c367281 100644
--- a/format/src/pretty_print.rs
+++ b/format/src/pretty_print.rs
@@ -16,7 +16,7 @@ use base::{
     metadata::Attribute,
     pos::{self, BytePos, HasSpan, Span, Spanned},
     source,
-    types::{self, ArgType, AsId,Prec, Type},
+    types::{self, ArgType, AsId, Prec, Type},
 };
 
 const INDENT: isize = 4;
@@ -478,24 +478,29 @@ where
                 ref bound,
                 ref body,
                 ..
-            }) => {
-                let from = match id {
-                    Some(pattern) => chain![
+            }) => match id {
+                Some(pattern) => {
+                    let from = chain![
                         arena,
                         "do",
                         self.space_before(pattern.span.start()),
                         self.pretty_pattern(pattern),
                         self.space_after(pattern.span.end()),
                         "="
-                    ],
-                    None => arena.text("seq"),
-                };
-                chain![
+                    ];
+                    chain![
+                        arena,
+                        self.hang(from, (self.space_before(bound.span.start()), true), bound),
+                        self.pretty_expr_(bound.span.end(), body)
+                    ]
+                }
+
+                None => chain![
                     arena,
-                    self.hang(from, (self.space_before(bound.span.start()), true), bound),
+                    self.pretty_expr_(bound.span.start(), bound),
                     self.pretty_expr_(bound.span.end(), body)
-                ]
-            }
+                ],
+            },
             Expr::MacroExpansion { ref original, .. } => {
                 return self.pretty_expr_(previous_end, original);
             }
diff --git a/format/tests/pretty_print.rs b/format/tests/pretty_print.rs
index 856fa504ea..21aa9847f7 100644
--- a/format/tests/pretty_print.rs
+++ b/format/tests/pretty_print.rs
@@ -4,7 +4,7 @@ extern crate pretty_assertions;
 extern crate gluon_base as base;
 extern crate gluon_format as format;
 
-use difference::assert_diff;
+use {difference::assert_diff, expect_test::expect};
 
 use gluon::{RootedThread, ThreadExt, VmBuilder};
 
@@ -813,3 +813,26 @@ let assert_success : [Show e]
 ()
 "#
 }
+
+#[test]
+fn sequence() {
+    let expr = r#"
+// a
+io.print "Hello"
+// b
+io.print " "
+// c
+io.println "World"
+// d
+"#;
+    expect![[r#"
+
+        // a
+        io.print "Hello"
+        // b
+        io.print " "
+        // c
+        io.println "World"
+        // d
+    "#]].assert_eq(&format_expr(expr).unwrap());
+}
diff --git a/std/parser.glu b/std/parser.glu
index bb8c9fd7b9..5b8f8f1b01 100644
--- a/std/parser.glu
+++ b/std/parser.glu
@@ -218,7 +218,7 @@ rec
 let skip_many p : Parser a -> Parser () = skip_many1 p <|> wrap ()
 /// Parses with `p` one or more times, ignoring the result of the parser
 let skip_many1 p : Parser a -> Parser () =
-    seq p
+    p
     skip_many p
 in
 /// Parses one of the characters of `s`