From 0e38362d244f118565f447f8ee2c6b8a700d05bf Mon Sep 17 00:00:00 2001
From: Isaac Freund <ifreund@ifreund.xyz>
Date: Sun, 7 Feb 2021 22:26:43 +0100
Subject: [PATCH] zig fmt: split Slice and SliceSentinel

This saves 4 whole bytes in the common case where there is no sentinel.
---
 lib/std/zig/ast.zig    | 41 ++++++++++++++++++++++++++++++-------
 lib/std/zig/parse.zig  | 46 ++++++++++++++++++++++++++----------------
 lib/std/zig/render.zig |  1 +
 3 files changed, 64 insertions(+), 24 deletions(-)

diff --git a/lib/std/zig/ast.zig b/lib/std/zig/ast.zig
index bebacd0b2d..815d783234 100644
--- a/lib/std/zig/ast.zig
+++ b/lib/std/zig/ast.zig
@@ -304,6 +304,7 @@ pub const Tree = struct {
             .BoolOr,
             .SliceOpen,
             .Slice,
+            .SliceSentinel,
             .Deref,
             .ArrayAccess,
             .ArrayInitOne,
@@ -694,19 +695,22 @@ pub const Tree = struct {
                     return main_tokens[n] + end_offset;
                 }
             },
+
             .SliceOpen => {
                 end_offset += 2; // ellipsis2 and rbracket
                 n = datas[n].rhs;
             },
             .Slice => {
                 const extra = tree.extraData(datas[n].rhs, Node.Slice);
-                if (extra.sentinel != 0) {
-                    n = extra.sentinel;
-                } else {
-                    assert(extra.end != 0); // should have used SliceOpen if end and sentinel are 0
-                    n = extra.end;
-                }
+                assert(extra.end != 0); // should have used SliceOpen
                 end_offset += 1; // rbracket
+                n = extra.end;
+            },
+            .SliceSentinel => {
+                const extra = tree.extraData(datas[n].rhs, Node.SliceSentinel);
+                assert(extra.sentinel != 0); // should have used Slice
+                end_offset += 1; // rbracket
+                n = extra.sentinel;
             },
 
             // These are not supported by lastToken() because implementation would
@@ -1129,6 +1133,21 @@ pub const Tree = struct {
         assert(tree.nodes.items(.tag)[node] == .Slice);
         const data = tree.nodes.items(.data)[node];
         const extra = tree.extraData(data.rhs, Node.Slice);
+        return .{
+            .ast = .{
+                .sliced = data.lhs,
+                .lbracket = tree.nodes.items(.main_token)[node],
+                .start = extra.start,
+                .end = extra.end,
+                .sentinel = 0,
+            },
+        };
+    }
+
+    pub fn sliceSentinel(tree: Tree, node: Node.Index) Full.Slice {
+        assert(tree.nodes.items(.tag)[node] == .SliceSentinel);
+        const data = tree.nodes.items(.data)[node];
+        const extra = tree.extraData(data.rhs, Node.SliceSentinel);
         return .{
             .ast = .{
                 .sliced = data.lhs,
@@ -1922,9 +1941,12 @@ pub const Node = struct {
         /// `lhs[rhs..]`
         /// main_token is the lbracket.
         SliceOpen,
-        /// `lhs[b..c :d]`. rhs is index into Slice
+        /// `lhs[b..c]`. rhs is index into Slice
         /// main_token is the lbracket.
         Slice,
+        /// `lhs[b..c :d]`. rhs is index into SliceSentinel
+        /// main_token is the lbracket.
+        SliceSentinel,
         /// `lhs.*`. rhs is unused.
         Deref,
         /// `lhs[rhs]`.
@@ -2202,6 +2224,11 @@ pub const Node = struct {
     pub const Slice = struct {
         start: Index,
         end: Index,
+    };
+
+    pub const SliceSentinel = struct {
+        start: Index,
+        end: Index,
         sentinel: Index,
     };
 
diff --git a/lib/std/zig/parse.zig b/lib/std/zig/parse.zig
index fc4847249a..31182c4952 100644
--- a/lib/std/zig/parse.zig
+++ b/lib/std/zig/parse.zig
@@ -3326,23 +3326,35 @@ const Parser = struct {
                             },
                         });
                     }
-                    const sentinel: Node.Index = if (p.eatToken(.Colon)) |_|
-                        try p.parseExpr()
-                    else
-                        0;
-                    _ = try p.expectToken(.RBracket);
-                    return p.addNode(.{
-                        .tag = .Slice,
-                        .main_token = lbracket,
-                        .data = .{
-                            .lhs = lhs,
-                            .rhs = try p.addExtra(.{
-                                .start = index_expr,
-                                .end = end_expr,
-                                .sentinel = sentinel,
-                            }),
-                        },
-                    });
+                    if (p.eatToken(.Colon)) |_| {
+                        const sentinel = try p.parseExpr();
+                        _ = try p.expectToken(.RBracket);
+                        return p.addNode(.{
+                            .tag = .SliceSentinel,
+                            .main_token = lbracket,
+                            .data = .{
+                                .lhs = lhs,
+                                .rhs = try p.addExtra(Node.SliceSentinel{
+                                    .start = index_expr,
+                                    .end = end_expr,
+                                    .sentinel = sentinel,
+                                }),
+                            },
+                        });
+                    } else {
+                        _ = try p.expectToken(.RBracket);
+                        return p.addNode(.{
+                            .tag = .Slice,
+                            .main_token = lbracket,
+                            .data = .{
+                                .lhs = lhs,
+                                .rhs = try p.addExtra(Node.Slice{
+                                    .start = index_expr,
+                                    .end = end_expr,
+                                }),
+                            },
+                        });
+                    }
                 }
                 _ = try p.expectToken(.RBracket);
                 return p.addNode(.{
diff --git a/lib/std/zig/render.zig b/lib/std/zig/render.zig
index cbaf462166..1c18d15219 100644
--- a/lib/std/zig/render.zig
+++ b/lib/std/zig/render.zig
@@ -470,6 +470,7 @@ fn renderExpression(ais: *Ais, tree: ast.Tree, node: ast.Node.Index, space: Spac
 
         .SliceOpen => try renderSlice(ais, tree, tree.sliceOpen(node), space),
         .Slice => try renderSlice(ais, tree, tree.slice(node), space),
+        .SliceSentinel => try renderSlice(ais, tree, tree.sliceSentinel(node), space),
 
         .Deref => {
             try renderExpression(ais, tree, datas[node].lhs, .None);