feat: support half_open_range syntax

Author: calebcartwright

rustfmt-core/rustfmt-lib/src/expr.rs

@@ -42,6 +42,17 @@ impl Rewrite for ast::Expr {
     }
 }
 
+impl Rewrite for Option<ptr::P<ast::Expr>> {
+    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
+        match &self {
+            None => Some("".to_owned()),
+            Some(ref exp) => {
+                exp.rewrite(context, shape)
+            }
+        }
+    }
+}
+
 #[derive(Copy, Clone, PartialEq)]
 pub(crate) enum ExprType {
     Statement,

rustfmt-core/rustfmt-lib/src/patterns.rs

@@ -179,28 +179,33 @@ impl Rewrite for Pat {
                     None
                 }
             }
-            PatKind::Range(ref lhs, ref rhs, ref end_kind) => match (lhs, rhs) {
-                (Some(lhs), Some(rhs)) => {
-                    let infix = match end_kind.node {
-                        RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
-                        RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
-                        RangeEnd::Excluded => "..",
+            PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
+                let infix = match end_kind.node {
+                    RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
+                    RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
+                    RangeEnd::Excluded => "..",
+                };
+                let infix = if context.config.spaces_around_ranges() {
+                    let lhs_spacing = match lhs {
+                        None => "",
+                        Some(_) => " ",
                     };
-                    let infix = if context.config.spaces_around_ranges() {
-                        format!(" {} ", infix)
-                    } else {
-                        infix.to_owned()
+                    let rhs_spacing = match rhs {
+                        None => "",
+                        Some(_) => " ",
                     };
-                    rewrite_pair(
-                        &**lhs,
-                        &**rhs,
-                        PairParts::infix(&infix),
-                        context,
-                        shape,
-                        SeparatorPlace::Front,
-                    )
-                },
-                (_, _) => unimplemented!(),
+                    format!("{}{}{}", lhs_spacing, infix, rhs_spacing)
+                } else {
+                    infix.to_owned()
+                };
+                rewrite_pair(
+                    lhs,
+                    rhs,
+                    PairParts::infix(&infix),
+                    context,
+                    shape,
+                    SeparatorPlace::Front,
+                )
             }
             PatKind::Ref(ref pat, mutability) => {
                 let prefix = format!("&{}", format_mutability(mutability));

rustfmt-core/rustfmt-lib/tests/source/configs/spaces_around_ranges/false.rs

@@ -20,3 +20,15 @@ fn main() {
         _ => bar,
     }
 }
+
+fn half_open() {
+    match [5 .. 4, 99 .. 105, 43 .. 44] {
+        [_, 99 .., _] => {}
+        [_, .. 105, _] => {}
+        _ => {}
+    };
+
+    if let ..=   5 = 0 {}
+    if let .. 5 = 0 {}
+    if let 5 .. = 0 {}
+}

rustfmt-core/rustfmt-lib/tests/source/configs/spaces_around_ranges/true.rs

@@ -20,3 +20,15 @@ fn main() {
         _ => bar,
     }
 }
+
+fn half_open() {
+    match [5..4, 99..105, 43..44] {
+        [_, 99.., _] => {}
+        [_, ..105, _] => {}
+        _ => {}
+    };
+
+    if let ..=5 = 0 {}
+    if let ..5 = 0 {}
+    if let 5.. = 0 {}
+}

rustfmt-core/rustfmt-lib/tests/target/configs/spaces_around_ranges/false.rs

@@ -20,3 +20,15 @@ fn main() {
         _ => bar,
     }
 }
+
+fn half_open() {
+    match [5..4, 99..105, 43..44] {
+        [_, 99.., _] => {}
+        [_, ..105, _] => {}
+        _ => {}
+    };
+
+    if let ..=5 = 0 {}
+    if let ..5 = 0 {}
+    if let 5.. = 0 {}
+}

rustfmt-core/rustfmt-lib/tests/target/configs/spaces_around_ranges/true.rs

@@ -20,3 +20,15 @@ fn main() {
         _ => bar,
     }
 }
+
+fn half_open() {
+    match [5 .. 4, 99 .. 105, 43 .. 44] {
+        [_, 99 .., _] => {}
+        [_, .. 105, _] => {}
+        _ => {}
+    };
+
+    if let ..= 5 = 0 {}
+    if let .. 5 = 0 {}
+    if let 5 .. = 0 {}
+}