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std.zig: resolve syntactic ambiguity

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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.
This commit is contained in:
mlugg 2024-04-29 02:25:54 +01:00
parent 5e12ca9fe3
commit 0cc8435a83
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GPG Key ID: 3F5B7DCCBF4AF02E
2 changed files with 24 additions and 14 deletions
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20
lib/std/zig/Ast.zig
View File

@ -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(.{
.switch_token = tree.nodes.items(.main_token)[node],
.condition = data.lhs,
.sub_range = data.rhs,
});
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,
};
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

18
lib/std/zig/Parse.zig
View File

@ -1245,7 +1245,7 @@ fn parseLabeledStatement(p: *Parse) !Node.Index {
const loop_stmt = try p.parseLoopStatement();
if (loop_stmt != 0) return loop_stmt;
const switch_expr = try p.parseSwitchExpr();
const switch_expr = try p.parseSwitchExpr(label_token != 0);
if (switch_expr != 0) return switch_expr;
if (label_token != 0) {
@ -2699,7 +2699,7 @@ fn parsePrimaryTypeExpr(p: *Parse) !Node.Index {
.builtin => return p.parseBuiltinCall(),
.keyword_fn => return p.parseFnProto(),
.keyword_if => return p.parseIf(expectTypeExpr),
.keyword_switch => return p.expectSwitchExpr(),
.keyword_switch => return p.expectSwitchExpr(false),
.keyword_extern,
.keyword_packed,
@ -2756,7 +2756,7 @@ fn parsePrimaryTypeExpr(p: *Parse) !Node.Index {
},
.keyword_switch => {
p.tok_i += 2;
return p.expectSwitchExpr();
return p.expectSwitchExpr(true);
},
.l_brace => {
p.tok_i += 2;
@ -3034,17 +3034,17 @@ fn parseWhileTypeExpr(p: *Parse) !Node.Index {
}
/// SwitchExpr <- KEYWORD_switch LPAREN Expr RPAREN LBRACE SwitchProngList RBRACE
fn parseSwitchExpr(p: *Parse) !Node.Index {
fn parseSwitchExpr(p: *Parse, is_labeled: bool) !Node.Index {
const switch_token = p.eatToken(.keyword_switch) orelse return null_node;
return p.expectSwitchSuffix(switch_token);
return p.expectSwitchSuffix(if (is_labeled) switch_token - 2 else switch_token);
}
fn expectSwitchExpr(p: *Parse) !Node.Index {
fn expectSwitchExpr(p: *Parse, is_labeled: bool) !Node.Index {
const switch_token = p.assertToken(.keyword_switch);
return p.expectSwitchSuffix(switch_token);
return p.expectSwitchSuffix(if (is_labeled) switch_token - 2 else switch_token);
}
fn expectSwitchSuffix(p: *Parse, switch_token: TokenIndex) !Node.Index {
fn expectSwitchSuffix(p: *Parse, main_token: TokenIndex) !Node.Index {
_ = try p.expectToken(.l_paren);
const expr_node = try p.expectExpr();
_ = try p.expectToken(.r_paren);
@ -3055,7 +3055,7 @@ fn expectSwitchSuffix(p: *Parse, switch_token: TokenIndex) !Node.Index {
return p.addNode(.{
.tag = if (trailing_comma) .switch_comma else .@"switch",
.main_token = switch_token,
.main_token = main_token,
.data = .{
.lhs = expr_node,
.rhs = try p.addExtra(Node.SubRange{