Commit 0cc8435a830d9d3850add163be4f12e5bd4f2f5c | zig

author	Matthew Lugg <mlugg@mlugg.co.uk> 2024-04-29 02:25:54+01:00
committer	Matthew Lugg <mlugg@mlugg.co.uk> 2024-09-01 18:30:31+01:00
log	0cc8435a830d9d3850add163be4f12e5bd4f2f5c
tree	f2b11a2c14628ed80865e6336ef2237504a107a7
parent	5e12ca9fe3c77ce1d2a3ea1c22c4bcb6d9b2bb0c
signature	Commit is signed but in an unrecognized format.

std.zig: resolve syntactic ambiguity

The parse of `fn foo(a: switch (...) { ... })` was previously handled
incorrectly; `a` was treated as both the parameter name and a label.

The same issue exists for `for` and `while` expressions -- they should
be fixed too, and the grammar amended appropriately. This commit does
not do this: it only aims to avoid introducing regressions from labeled
switch syntax.

2 files changed, 24 insertions(+), 14 deletions(-)

lib
- std
  - zig
    Ast.zig
    Parse.zig

lib/std/zig/Ast.zig+15-5

 @@ -1890,11 +1890,20 @@ 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];
-    return tree.fullSwitchComponents(.{
+    const main_token = tree.nodes.items(.main_token)[node];
-        .switch_token = tree.nodes.items(.main_token)[node],
+    const switch_token: TokenIndex, const label_token: ?TokenIndex = switch (tree.tokens.items(.tag)[main_token]) {
-        .condition = data.lhs,
+        .identifier => .{ main_token + 2, main_token },
-        .sub_range = data.rhs,
+        .keyword_switch => .{ main_token, null },
-    });
+        else => unreachable,
+    };
+    return .{
+        .ast = .{
+            .switch_token = switch_token,
+            .condition = data.lhs,
+            .sub_range = data.rhs,
+        },
+        .label_token = label_token,
+    };
 }
 pub fn switchCaseOne(tree: Ast, node: Node.Index) full.SwitchCase {
 @@ -3278,6 +3287,7 @@ 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

lib/std/zig/Parse.zig+9-9

...	@@ -1245,7 +1245,7 @@ fn parseLabeledStatement(p: *Parse) !Node.Index {	...	@@ -1245,7 +1245,7 @@ fn parseLabeledStatement(p: *Parse) !Node.Index {
1245	const loop_stmt = try p.parseLoopStatement();	1245	const loop_stmt = try p.parseLoopStatement();
1246	if (loop_stmt != 0) return loop_stmt;	1246	if (loop_stmt != 0) return loop_stmt;
1247		1247
1248	const switch_expr = try p.parseSwitchExpr();	1248	const switch_expr = try p.parseSwitchExpr(label_token != 0);
1249	if (switch_expr != 0) return switch_expr;	1249	if (switch_expr != 0) return switch_expr;
1250		1250
1251	if (label_token != 0) {	1251	if (label_token != 0) {
...	@@ -2699,7 +2699,7 @@ fn parsePrimaryTypeExpr(p: *Parse) !Node.Index {	...	@@ -2699,7 +2699,7 @@ fn parsePrimaryTypeExpr(p: *Parse) !Node.Index {
2699	.builtin => return p.parseBuiltinCall(),	2699	.builtin => return p.parseBuiltinCall(),
2700	.keyword_fn => return p.parseFnProto(),	2700	.keyword_fn => return p.parseFnProto(),
2701	.keyword_if => return p.parseIf(expectTypeExpr),	2701	.keyword_if => return p.parseIf(expectTypeExpr),
2702	.keyword_switch => return p.expectSwitchExpr(),	2702	.keyword_switch => return p.expectSwitchExpr(false),
2703		2703
2704	.keyword_extern,	2704	.keyword_extern,
2705	.keyword_packed,	2705	.keyword_packed,
...	@@ -2756,7 +2756,7 @@ fn parsePrimaryTypeExpr(p: *Parse) !Node.Index {	...	@@ -2756,7 +2756,7 @@ fn parsePrimaryTypeExpr(p: *Parse) !Node.Index {
2756	},	2756	},
2757	.keyword_switch => {	2757	.keyword_switch => {
2758	p.tok_i += 2;	2758	p.tok_i += 2;
2759	return p.expectSwitchExpr();	2759	return p.expectSwitchExpr(true);
2760	},	2760	},
2761	.l_brace => {	2761	.l_brace => {
2762	p.tok_i += 2;	2762	p.tok_i += 2;
...	@@ -3034,17 +3034,17 @@ fn parseWhileTypeExpr(p: *Parse) !Node.Index {	...	@@ -3034,17 +3034,17 @@ fn parseWhileTypeExpr(p: *Parse) !Node.Index {
3034	}	3034	}
3035		3035
3036	/// SwitchExpr <- KEYWORD_switch LPAREN Expr RPAREN LBRACE SwitchProngList RBRACE	3036	/// SwitchExpr <- KEYWORD_switch LPAREN Expr RPAREN LBRACE SwitchProngList RBRACE
3037	fn parseSwitchExpr(p: *Parse) !Node.Index {	3037	fn parseSwitchExpr(p: *Parse, is_labeled: bool) !Node.Index {
3038	const switch_token = p.eatToken(.keyword_switch) orelse return null_node;	3038	const switch_token = p.eatToken(.keyword_switch) orelse return null_node;
3039	return p.expectSwitchSuffix(switch_token);	3039	return p.expectSwitchSuffix(if (is_labeled) switch_token - 2 else switch_token);
3040	}	3040	}
3041		3041
3042	fn expectSwitchExpr(p: *Parse) !Node.Index {	3042	fn expectSwitchExpr(p: *Parse, is_labeled: bool) !Node.Index {
3043	const switch_token = p.assertToken(.keyword_switch);	3043	const switch_token = p.assertToken(.keyword_switch);
3044	return p.expectSwitchSuffix(switch_token);	3044	return p.expectSwitchSuffix(if (is_labeled) switch_token - 2 else switch_token);
3045	}	3045	}
3046		3046
3047	fn expectSwitchSuffix(p: *Parse, switch_token: TokenIndex) !Node.Index {	3047	fn expectSwitchSuffix(p: *Parse, main_token: TokenIndex) !Node.Index {
3048	_ = try p.expectToken(.l_paren);	3048	_ = try p.expectToken(.l_paren);
3049	const expr_node = try p.expectExpr();	3049	const expr_node = try p.expectExpr();
3050	_ = try p.expectToken(.r_paren);	3050	_ = try p.expectToken(.r_paren);
...	@@ -3055,7 +3055,7 @@ fn expectSwitchSuffix(p: *Parse, switch_token: TokenIndex) !Node.Index {	...	@@ -3055,7 +3055,7 @@ fn expectSwitchSuffix(p: *Parse, switch_token: TokenIndex) !Node.Index {
3055		3055
3056	return p.addNode(.{	3056	return p.addNode(.{
3057	.tag = if (trailing_comma) .switch_comma else .@"switch",	3057	.tag = if (trailing_comma) .switch_comma else .@"switch",
3058	.main_token = switch_token,	3058	.main_token = main_token,
3059	.data = .{	3059	.data = .{
3060	.lhs = expr_node,	3060	.lhs = expr_node,
3061	.rhs = try p.addExtra(Node.SubRange{	3061	.rhs = try p.addExtra(Node.SubRange{