Merge pull request #21257 from mlugg/computed-goto-3

compiler: implement labeled switch/continue

Author: andrewrk

lib/std/zig/Ast.zig

@@ -1184,14 +1184,7 @@ pub fn lastToken(tree: Ast, node: Node.Index) TokenIndex {
             n = extra.sentinel;
         },
 
-        .@"continue" => {
-            if (datas[n].lhs != 0) {
-                return datas[n].lhs + end_offset;
-            } else {
-                return main_tokens[n] + end_offset;
-            }
-        },
-        .@"break" => {
+        .@"continue", .@"break" => {
             if (datas[n].rhs != 0) {
                 n = datas[n].rhs;
             } else if (datas[n].lhs != 0) {
@@ -1895,6 +1888,25 @@ pub fn taggedUnionEnumTag(tree: Ast, node: Node.Index) full.ContainerDecl {
     });
 }
 
+pub fn switchFull(tree: Ast, node: Node.Index) full.Switch {
+    const data = &tree.nodes.items(.data)[node];
+    const main_token = tree.nodes.items(.main_token)[node];
+    const switch_token: TokenIndex, const label_token: ?TokenIndex = switch (tree.tokens.items(.tag)[main_token]) {
+        .identifier => .{ main_token + 2, main_token },
+        .keyword_switch => .{ main_token, null },
+        else => unreachable,
+    };
+    const extra = tree.extraData(data.rhs, Ast.Node.SubRange);
+    return .{
+        .ast = .{
+            .switch_token = switch_token,
+            .condition = data.lhs,
+            .cases = tree.extra_data[extra.start..extra.end],
+        },
+        .label_token = label_token,
+    };
+}
+
 pub fn switchCaseOne(tree: Ast, node: Node.Index) full.SwitchCase {
     const data = &tree.nodes.items(.data)[node];
     const values: *[1]Node.Index = &data.lhs;
@@ -2206,6 +2218,21 @@ fn fullContainerDeclComponents(tree: Ast, info: full.ContainerDecl.Components) f
     return result;
 }
 
+fn fullSwitchComponents(tree: Ast, info: full.Switch.Components) full.Switch {
+    const token_tags = tree.tokens.items(.tag);
+    const tok_i = info.switch_token -| 1;
+    var result: full.Switch = .{
+        .ast = info,
+        .label_token = null,
+    };
+    if (token_tags[tok_i] == .colon and
+        token_tags[tok_i -| 1] == .identifier)
+    {
+        result.label_token = tok_i - 1;
+    }
+    return result;
+}
+
 fn fullSwitchCaseComponents(tree: Ast, info: full.SwitchCase.Components, node: Node.Index) full.SwitchCase {
     const token_tags = tree.tokens.items(.tag);
     const node_tags = tree.nodes.items(.tag);
@@ -2477,6 +2504,13 @@ pub fn fullContainerDecl(tree: Ast, buffer: *[2]Ast.Node.Index, node: Node.Index
     };
 }
 
+pub fn fullSwitch(tree: Ast, node: Node.Index) ?full.Switch {
+    return switch (tree.nodes.items(.tag)[node]) {
+        .@"switch", .switch_comma => tree.switchFull(node),
+        else => null,
+    };
+}
+
 pub fn fullSwitchCase(tree: Ast, node: Node.Index) ?full.SwitchCase {
     return switch (tree.nodes.items(.tag)[node]) {
         .switch_case_one, .switch_case_inline_one => tree.switchCaseOne(node),
@@ -2829,6 +2863,17 @@ pub const full = struct {
         };
     };
 
+    pub const Switch = struct {
+        ast: Components,
+        label_token: ?TokenIndex,
+
+        pub const Components = struct {
+            switch_token: TokenIndex,
+            condition: Node.Index,
+            cases: []const Node.Index,
+        };
+    };
+
     pub const SwitchCase = struct {
         inline_token: ?TokenIndex,
         /// Points to the first token after the `|`. Will either be an identifier or
@@ -3243,6 +3288,7 @@ pub const Node = struct {
         /// main_token is the `(`.
         async_call_comma,
         /// `switch(lhs) {}`. `SubRange[rhs]`.
+        /// `main_token` is the identifier of a preceding label, if any; otherwise `switch`.
         @"switch",
         /// Same as switch except there is known to be a trailing comma
         /// before the final rbrace
@@ -3287,7 +3333,8 @@ pub const Node = struct {
         @"suspend",
         /// `resume lhs`. rhs is unused.
         @"resume",
-        /// `continue`. lhs is token index of label if any. rhs is unused.
+        /// `continue :lhs rhs`
+        /// both lhs and rhs may be omitted.
         @"continue",
         /// `break :lhs rhs`
         /// both lhs and rhs may be omitted.