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AstGen: improve ergonomics of Scope

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Adds `Scope.Unwrapped`, a simple union of pointers to already-casted scopes
with `Scope.Tag` as its tag enum. This pairs very nicely with labeled switch
and gets rid of almost every `scope.cast(...).?`, improving developer QOL :)
This commit is contained in:
Justus Klausecker 2025-12-17 20:01:36 +01:00 • committed by Matthew Lugg
parent e0108dec54
commit d840bb5118
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GPG key ID: 3F5B7DCCBF4AF02E
1 changed files with 122 additions and 155 deletions
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277
lib/std/zig/AstGen.zig
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@ -2161,10 +2161,9 @@ fn breakExpr(parent_gz: *GenZir, parent_scope: *Scope, node: Ast.Node.Index) Inn
const opt_break_label, const opt_rhs = tree.nodeData(node).opt_token_and_opt_node;
// Look for the label in the scope.
var scope = parent_scope;
find_scope: switch (scope.tag) {
.gen_zir => {
const gen_zir = scope.cast(GenZir).?;
find_scope: switch (parent_scope.unwrap()) {
.gen_zir => |gen_zir| {
const scope = &gen_zir.base;
if (gen_zir.cur_defer_node.unwrap()) |cur_defer_node| {
// We are breaking out of a `defer` block.
@ -2185,13 +2184,11 @@ fn breakExpr(parent_gz: *GenZir, parent_scope: *Scope, node: Ast.Node.Index) Inn
}
}
// gz without or with different label, continue to parent scopes.
scope = gen_zir.parent;
continue :find_scope scope.tag;
continue :find_scope gen_zir.parent.unwrap();
} else if (!gen_zir.allow_unlabeled_control_flow) {
// This `break` is unlabeled and the gz we've found doesn't allow
// unlabeled control flow. Continue to parent scopes.
scope = gen_zir.parent;
continue :find_scope scope.tag;
continue :find_scope gen_zir.parent.unwrap();
}
const break_tag: Zir.Inst.Tag = if (gen_zir.is_inline)
@ -2236,18 +2233,9 @@ fn breakExpr(parent_gz: *GenZir, parent_scope: *Scope, node: Ast.Node.Index) Inn
return .unreachable_value;
}
},
.local_val => {
scope = scope.cast(Scope.LocalVal).?.parent;
continue :find_scope scope.tag;
},
.local_ptr => {
scope = scope.cast(Scope.LocalPtr).?.parent;
continue :find_scope scope.tag;
},
.defer_normal, .defer_error => {
scope = scope.cast(Scope.Defer).?.parent;
continue :find_scope scope.tag;
},
.local_val => |local_val| continue :find_scope local_val.parent.unwrap(),
.local_ptr => |local_ptr| continue :find_scope local_ptr.parent.unwrap(),
.defer_normal, .defer_error => |defer_scope| continue :find_scope defer_scope.parent.unwrap(),
.namespace => {
if (opt_break_label.unwrap()) |break_label| {
const label_name = try astgen.identifierTokenString(break_label);
@ -2270,10 +2258,9 @@ fn continueExpr(parent_gz: *GenZir, parent_scope: *Scope, node: Ast.Node.Index)
}
// Look for the label in the scope.
var scope = parent_scope;
find_scope: switch (scope.tag) {
.gen_zir => {
const gen_zir = scope.cast(GenZir).?;
find_scope: switch (parent_scope.unwrap()) {
.gen_zir => |gen_zir| {
const scope = &gen_zir.base;
if (gen_zir.cur_defer_node.unwrap()) |cur_defer_node| {
return astgen.failNodeNotes(node, "cannot continue out of defer expression", .{}, &.{
@ -2305,24 +2292,21 @@ fn continueExpr(parent_gz: *GenZir, parent_scope: *Scope, node: Ast.Node.Index)
}
}
// gz without or with different label, continue to parent scopes.
scope = gen_zir.parent;
continue :find_scope scope.tag;
continue :find_scope gen_zir.parent.unwrap();
} else if (gen_zir.allow_unlabeled_control_flow) {
// This `continue` is unlabeled. If the gz we've found doesn't
// provide a `continue` target or corresponds to a labeled
// `switch`, ignore it and continue to parent scopes.
switch (gen_zir.continue_target) {
.none, .switch_continue => {
scope = gen_zir.parent;
continue :find_scope scope.tag;
continue :find_scope gen_zir.parent.unwrap();
},
.@"break" => {},
}
} else {
// We don't have a break label and the gz we found doesn't allow
// unlabeled control flow, so we continue to its parent scopes.
scope = gen_zir.parent;
continue :find_scope scope.tag;
continue :find_scope gen_zir.parent.unwrap();
}
switch (gen_zir.continue_target) {
@ -2360,18 +2344,9 @@ fn continueExpr(parent_gz: *GenZir, parent_scope: *Scope, node: Ast.Node.Index)
},
}
},
.local_val => {
scope = scope.cast(Scope.LocalVal).?.parent;
continue :find_scope scope.tag;
},
.local_ptr => {
scope = scope.cast(Scope.LocalPtr).?.parent;
continue :find_scope scope.tag;
},
.defer_normal, .defer_error => {
scope = scope.cast(Scope.Defer).?.parent;
continue :find_scope scope.tag;
},
.local_val => |local_val| continue :find_scope local_val.parent.unwrap(),
.local_ptr => |local_ptr| continue :find_scope local_ptr.parent.unwrap(),
.defer_normal, .defer_error => |defer_scope| continue :find_scope defer_scope.parent.unwrap(),
.namespace => {
if (opt_break_label.unwrap()) |break_label| {
const label_name = try astgen.identifierTokenString(break_label);
@ -2466,33 +2441,29 @@ fn blockExpr(
fn checkLabelRedefinition(astgen: *AstGen, parent_scope: *Scope, label: Ast.TokenIndex) !void {
// Look for the label in the scope.
var scope = parent_scope;
while (true) {
switch (scope.tag) {
.gen_zir => {
const gen_zir = scope.cast(GenZir).?;
if (gen_zir.label) |prev_label| {
if (try astgen.tokenIdentEql(label, prev_label.token)) {
const label_name = try astgen.identifierTokenString(label);
return astgen.failTokNotes(label, "redefinition of label '{s}'", .{
label_name,
}, &[_]u32{
try astgen.errNoteTok(
prev_label.token,
"previous definition here",
.{},
),
});
}
find_scope: switch (parent_scope.unwrap()) {
.gen_zir => |gen_zir| {
if (gen_zir.label) |prev_label| {
if (try astgen.tokenIdentEql(label, prev_label.token)) {
const label_name = try astgen.identifierTokenString(label);
return astgen.failTokNotes(label, "redefinition of label '{s}'", .{
label_name,
}, &[_]u32{
try astgen.errNoteTok(
prev_label.token,
"previous definition here",
.{},
),
});
}
scope = gen_zir.parent;
},
.local_val => scope = scope.cast(Scope.LocalVal).?.parent,
.local_ptr => scope = scope.cast(Scope.LocalPtr).?.parent,
.defer_normal, .defer_error => scope = scope.cast(Scope.Defer).?.parent,
.namespace => break,
.top => unreachable,
}
}
continue :find_scope gen_zir.parent.unwrap();
},
.local_val => |local_val| continue :find_scope local_val.parent.unwrap(),
.local_ptr => |local_ptr| continue :find_scope local_ptr.parent.unwrap(),
.defer_normal, .defer_error => |defer_scope| continue :find_scope defer_scope.parent.unwrap(),
.namespace => break :find_scope,
.top => unreachable,
}
}
@ -3007,18 +2978,16 @@ fn countDefers(outer_scope: *Scope, inner_scope: *Scope) struct {
var need_err_code = false;
var scope = inner_scope;
while (scope != outer_scope) {
switch (scope.tag) {
.gen_zir => scope = scope.cast(GenZir).?.parent,
.local_val => scope = scope.cast(Scope.LocalVal).?.parent,
.local_ptr => scope = scope.cast(Scope.LocalPtr).?.parent,
.defer_normal => {
const defer_scope = scope.cast(Scope.Defer).?;
switch (scope.unwrap()) {
.gen_zir => |gen_zir| scope = gen_zir.parent,
.local_val => |local_val| scope = local_val.parent,
.local_ptr => |local_ptr| scope = local_ptr.parent,
.defer_normal => |defer_scope| {
scope = defer_scope.parent;
have_normal = true;
},
.defer_error => {
const defer_scope = scope.cast(Scope.Defer).?;
.defer_error => |defer_scope| {
scope = defer_scope.parent;
have_err = true;
@ -3054,17 +3023,15 @@ fn genDefers(
var scope = inner_scope;
while (scope != outer_scope) {
switch (scope.tag) {
.gen_zir => scope = scope.cast(GenZir).?.parent,
.local_val => scope = scope.cast(Scope.LocalVal).?.parent,
.local_ptr => scope = scope.cast(Scope.LocalPtr).?.parent,
.defer_normal => {
const defer_scope = scope.cast(Scope.Defer).?;
switch (scope.unwrap()) {
.gen_zir => |gen_zir| scope = gen_zir.parent,
.local_val => |local_val| scope = local_val.parent,
.local_ptr => |local_ptr| scope = local_ptr.parent,
.defer_normal => |defer_scope| {
scope = defer_scope.parent;
try gz.addDefer(defer_scope.index, defer_scope.len);
},
.defer_error => {
const defer_scope = scope.cast(Scope.Defer).?;
.defer_error => |defer_scope| {
scope = defer_scope.parent;
switch (which_ones) {
.both_sans_err => {
@ -3107,10 +3074,9 @@ fn checkUsed(gz: *GenZir, outer_scope: *Scope, inner_scope: *Scope) InnerError!v
var scope = inner_scope;
while (scope != outer_scope) {
switch (scope.tag) {
.gen_zir => scope = scope.cast(GenZir).?.parent,
.local_val => {
const s = scope.cast(Scope.LocalVal).?;
switch (scope.unwrap()) {
.gen_zir => |gen_zir| scope = gen_zir.parent,
.local_val => |s| {
if (s.used == .none and s.discarded == .none) {
try astgen.appendErrorTok(s.token_src, "unused {s}", .{@tagName(s.id_cat)});
} else if (s.used != .none and s.discarded != .none) {
@ -3120,8 +3086,7 @@ fn checkUsed(gz: *GenZir, outer_scope: *Scope, inner_scope: *Scope) InnerError!v
}
scope = s.parent;
},
.local_ptr => {
const s = scope.cast(Scope.LocalPtr).?;
.local_ptr => |s| {
if (s.used == .none and s.discarded == .none) {
try astgen.appendErrorTok(s.token_src, "unused {s}", .{@tagName(s.id_cat)});
} else {
@ -3136,10 +3101,9 @@ fn checkUsed(gz: *GenZir, outer_scope: *Scope, inner_scope: *Scope) InnerError!v
});
}
}
scope = s.parent;
},
.defer_normal, .defer_error => scope = scope.cast(Scope.Defer).?.parent,
.defer_normal, .defer_error => |defer_scope| scope = defer_scope.parent,
.namespace => unreachable,
.top => unreachable,
}
@ -4805,13 +4769,11 @@ fn testDecl(
// Local variables, including function parameters.
const name_str_index = try astgen.identAsString(test_name_token);
var s = scope;
var found_already: ?Ast.Node.Index = null; // we have found a decl with the same name already
var num_namespaces_out: u32 = 0;
var capturing_namespace: ?*Scope.Namespace = null;
while (true) switch (s.tag) {
.local_val => {
const local_val = s.cast(Scope.LocalVal).?;
find_scope: switch (scope.unwrap()) {
.local_val => |local_val| {
if (local_val.name == name_str_index) {
local_val.used = .fromToken(test_name_token);
return astgen.failTokNotes(test_name_token, "cannot test a {s}", .{
@ -4822,10 +4784,9 @@ fn testDecl(
}),
});
}
s = local_val.parent;
continue :find_scope local_val.parent.unwrap();
},
.local_ptr => {
const local_ptr = s.cast(Scope.LocalPtr).?;
.local_ptr => |local_ptr| {
if (local_ptr.name == name_str_index) {
local_ptr.used = .fromToken(test_name_token);
return astgen.failTokNotes(test_name_token, "cannot test a {s}", .{
@ -4836,12 +4797,11 @@ fn testDecl(
}),
});
}
s = local_ptr.parent;
continue :find_scope local_ptr.parent.unwrap();
},
.gen_zir => s = s.cast(GenZir).?.parent,
.defer_normal, .defer_error => s = s.cast(Scope.Defer).?.parent,
.namespace => {
const ns = s.cast(Scope.Namespace).?;
.gen_zir => |gen_zir| continue :find_scope gen_zir.parent.unwrap(),
.defer_normal, .defer_error => |defer_scope| continue :find_scope defer_scope.parent.unwrap(),
.namespace => |ns| {
if (ns.decls.get(name_str_index)) |i| {
if (found_already) |f| {
return astgen.failTokNotes(test_name_token, "ambiguous reference", .{}, &.{
@ -4854,10 +4814,10 @@ fn testDecl(
}
num_namespaces_out += 1;
capturing_namespace = ns;
s = ns.parent;
continue :find_scope ns.parent.unwrap();
},
.top => break,
};
.top => break :find_scope,
}
if (found_already == null) {
const ident_name = try astgen.identifierTokenString(test_name_token);
return astgen.failTok(test_name_token, "use of undeclared identifier '{s}'", .{ident_name});
@ -8409,7 +8369,6 @@ fn localVarRef(
) InnerError!Zir.Inst.Ref {
const astgen = gz.astgen;
const name_str_index = try astgen.identAsString(ident_token);
var s = scope;
var found_already: ?Ast.Node.Index = null; // we have found a decl with the same name already
var found_needs_tunnel: bool = undefined; // defined when `found_already != null`
var found_namespaces_out: u32 = undefined; // defined when `found_already != null`
@ -8419,10 +8378,8 @@ fn localVarRef(
// defined by `num_namespaces_out != 0`
var capturing_namespace: *Scope.Namespace = undefined;
while (true) switch (s.tag) {
.local_val => {
const local_val = s.cast(Scope.LocalVal).?;
find_scope: switch (scope.unwrap()) {
.local_val => |local_val| {
if (local_val.name == name_str_index) {
// Locals cannot shadow anything, so we do not need to look for ambiguous
// references in this case.
@ -8445,10 +8402,9 @@ fn localVarRef(
return rvalueNoCoercePreRef(gz, ri, value_inst, ident);
}
s = local_val.parent;
continue :find_scope local_val.parent.unwrap();
},
.local_ptr => {
const local_ptr = s.cast(Scope.LocalPtr).?;
.local_ptr => |local_ptr| {
if (local_ptr.name == name_str_index) {
if (ri.rl == .discard and ri.ctx == .assignment) {
local_ptr.discarded = .fromToken(ident_token);
@ -8497,12 +8453,11 @@ fn localVarRef(
},
}
}
s = local_ptr.parent;
continue :find_scope local_ptr.parent.unwrap();
},
.gen_zir => s = s.cast(GenZir).?.parent,
.defer_normal, .defer_error => s = s.cast(Scope.Defer).?.parent,
.namespace => {
const ns = s.cast(Scope.Namespace).?;
.gen_zir => |gen_zir| continue :find_scope gen_zir.parent.unwrap(),
.defer_normal, .defer_error => |defer_scope| continue :find_scope defer_scope.parent.unwrap(),
.namespace => |ns| {
if (ns.decls.get(name_str_index)) |i| {
if (found_already) |f| {
return astgen.failNodeNotes(ident, "ambiguous reference", .{}, &.{
@ -8517,10 +8472,10 @@ fn localVarRef(
}
num_namespaces_out += 1;
capturing_namespace = ns;
s = ns.parent;
continue :find_scope ns.parent.unwrap();
},
.top => break,
};
.top => break :find_scope,
}
if (found_already == null) {
const ident_name = try astgen.identifierTokenString(ident_token);
return astgen.failNode(ident, "use of undeclared identifier '{s}'", .{ident_name});
@ -11812,6 +11767,26 @@ const Scope = struct {
};
}
fn unwrap(base: *Scope) Unwrapped {
return switch (base.tag) {
inline else => |tag| @unionInit(
Unwrapped,
@tagName(tag),
@alignCast(@fieldParentPtr("base", base)),
),
};
}
const Unwrapped = union(Tag) {
gen_zir: *GenZir,
local_val: *LocalVal,
local_ptr: *LocalPtr,
defer_normal: *Defer,
defer_error: *Defer,
namespace: *Namespace,
top: *Top,
};
const Tag = enum {
gen_zir,
local_val,
@ -13408,11 +13383,9 @@ fn detectLocalShadowing(
});
}
var s = scope;
var outer_scope = false;
while (true) switch (s.tag) {
.local_val => {
const local_val = s.cast(Scope.LocalVal).?;
find_scope: switch (scope.unwrap()) {
.local_val => |local_val| {
if (local_val.name == ident_name) {
const name_slice = mem.span(astgen.nullTerminatedString(ident_name));
const name = try gpa.dupe(u8, name_slice);
@ -13438,10 +13411,9 @@ fn detectLocalShadowing(
),
});
}
s = local_val.parent;
continue :find_scope local_val.parent.unwrap();
},
.local_ptr => {
const local_ptr = s.cast(Scope.LocalPtr).?;
.local_ptr => |local_ptr| {
if (local_ptr.name == ident_name) {
const name_slice = mem.span(astgen.nullTerminatedString(ident_name));
const name = try gpa.dupe(u8, name_slice);
@ -13467,14 +13439,12 @@ fn detectLocalShadowing(
),
});
}
s = local_ptr.parent;
continue :find_scope local_ptr.parent.unwrap();
},
.namespace => {
.namespace => |ns| {
outer_scope = true;
const ns = s.cast(Scope.Namespace).?;
const decl_node = ns.decls.get(ident_name) orelse {
s = ns.parent;
continue;
continue :find_scope ns.parent.unwrap();
};
const name_slice = mem.span(astgen.nullTerminatedString(ident_name));
const name = try gpa.dupe(u8, name_slice);
@ -13485,13 +13455,13 @@ fn detectLocalShadowing(
try astgen.errNoteNode(decl_node, "declared here", .{}),
});
},
.gen_zir => {
s = s.cast(GenZir).?.parent;
.gen_zir => |gen_zir| {
outer_scope = true;
continue :find_scope gen_zir.parent.unwrap();
},
.defer_normal, .defer_error => s = s.cast(Scope.Defer).?.parent,
.top => break,
};
.defer_normal, .defer_error => |defer_scope| continue :find_scope defer_scope.parent.unwrap(),
.top => break :find_scope,
}
}
const LineColumn = struct { u32, u32 };
@ -13728,10 +13698,8 @@ fn scanContainer(
continue;
}
var s = namespace.parent;
while (true) switch (s.tag) {
.local_val => {
const local_val = s.cast(Scope.LocalVal).?;
find_scope: switch (namespace.parent.unwrap()) {
.local_val => |local_val| {
if (local_val.name == name_str_index) {
try astgen.appendErrorTokNotes(name_token, "declaration '{s}' shadows {s} from outer scope", .{
token_bytes, @tagName(local_val.id_cat),
@ -13743,12 +13711,11 @@ fn scanContainer(
),
});
any_invalid_declarations = true;
break;
break :find_scope;
}
s = local_val.parent;
continue :find_scope local_val.parent.unwrap();
},
.local_ptr => {
const local_ptr = s.cast(Scope.LocalPtr).?;
.local_ptr => |local_ptr| {
if (local_ptr.name == name_str_index) {
try astgen.appendErrorTokNotes(name_token, "declaration '{s}' shadows {s} from outer scope", .{
token_bytes, @tagName(local_ptr.id_cat),
@ -13760,15 +13727,15 @@ fn scanContainer(
),
});
any_invalid_declarations = true;
break;
break :find_scope;
}
s = local_ptr.parent;
continue :find_scope local_ptr.parent.unwrap();
},
.namespace => s = s.cast(Scope.Namespace).?.parent,
.gen_zir => s = s.cast(GenZir).?.parent,
.defer_normal, .defer_error => s = s.cast(Scope.Defer).?.parent,
.top => break,
};
.namespace => |ns| continue :find_scope ns.parent.unwrap(),
.gen_zir => |gen_zir| continue :find_scope gen_zir.parent.unwrap(),
.defer_normal, .defer_error => |defer_scope| continue :find_scope defer_scope.parent.unwrap(),
.top => break :find_scope,
}
}
if (!any_duplicates) {