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AstGen: support @export with field access

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The Zig language specification will support identifiers and field access
in order to refer to which declaration to export with `@export`.

This commit implements the change in AstGen and updates the language
reference.
This commit is contained in:
Andrew Kelley
2021-06-15 14:08:57 -07:00
parent 0f4173c5d8
commit 515d6430c0
4 changed files with 45 additions and 13 deletions
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15
doc/langref.html.in
View File

@@ -7525,13 +7525,22 @@ test "main" {
{#header_close#}
{#header_open|@export#}
<pre>{#syntax#}@export(identifier, comptime options: std.builtin.ExportOptions) void{#endsyntax#}</pre>
<pre>{#syntax#}@export(declaration, comptime options: std.builtin.ExportOptions) void{#endsyntax#}</pre>
<p>
Creates a symbol in the output object file.
</p>
<p>
This function can be called from a {#link|comptime#} block to conditionally export symbols.
When {#syntax#}identifier{#endsyntax#} is a function with the C calling convention and
<code>declaration</code> must be one of two things:
</p>
<ul>
<li>An identifier ({#syntax#}x{#endsyntax#}) identifying a {#link|function|Functions#} or
{#link|global variable|Global Variables#}.</li>
<li>Field access ({#syntax#}x.y{#endsyntax#}) looking up a {#link|function|Functions#} or
{#link|global variable|Global Variables#}.</li>
</ul>
<p>
This builtin can be called from a {#link|comptime#} block to conditionally export symbols.
When <code>declaration</code> is a function with the C calling convention and
{#syntax#}options.linkage{#endsyntax#} is {#syntax#}Strong{#endsyntax#}, this is equivalent to
the {#syntax#}export{#endsyntax#} keyword used on a function:
</p>

29
src/AstGen.zig
View File

@@ -6706,18 +6706,33 @@ fn builtinCall(
.@"export" => {
const node_tags = tree.nodes.items(.tag);
const node_datas = tree.nodes.items(.data);
// This function causes a Decl to be exported. The first parameter is not an expression,
// but an identifier of the Decl to be exported.
if (node_tags[params[0]] != .identifier) {
return astgen.failNode(params[0], "the first @export parameter must be an identifier", .{});
var namespace: Zir.Inst.Ref = .none;
var decl_name: u32 = 0;
switch (node_tags[params[0]]) {
.identifier => {
const ident_token = main_tokens[params[0]];
decl_name = try astgen.identAsString(ident_token);
// TODO look for local variables in scope matching `decl_name` and emit a compile
// error. Only top-level declarations can be exported. Until this is done, the
// compile error will end up being "use of undeclared identifier" in Sema.
},
.field_access => {
const namespace_node = node_datas[params[0]].lhs;
namespace = try typeExpr(gz, scope, namespace_node);
const dot_token = main_tokens[params[0]];
const field_ident = dot_token + 1;
decl_name = try astgen.identAsString(field_ident);
},
else => return astgen.failNode(
params[0], "the first @export parameter must be an identifier", .{},
),
}
const ident_token = main_tokens[params[0]];
const decl_name = try astgen.identAsString(ident_token);
// TODO look for local variables in scope matching `decl_name` and emit a compile
// error. Only top-level declarations can be exported. Until this is done, the
// compile error will end up being "use of undeclared identifier" in Sema.
const options = try comptimeExpr(gz, scope, .{ .ty = .export_options_type }, params[1]);
_ = try gz.addPlNode(.@"export", node, Zir.Inst.Export{
.namespace = namespace,
.decl_name = decl_name,
.options = options,
});

3
src/Sema.zig
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@@ -1985,6 +1985,9 @@ fn zirExport(sema: *Sema, block: *Scope.Block, inst: Zir.Inst.Index) InnerError!
const lhs_src: LazySrcLoc = .{ .node_offset_builtin_call_arg0 = inst_data.src_node };
const rhs_src: LazySrcLoc = .{ .node_offset_builtin_call_arg1 = inst_data.src_node };
const decl_name = sema.code.nullTerminatedString(extra.decl_name);
if (extra.namespace != .none) {
return sema.mod.fail(&block.base, src, "TODO: implement exporting with field access", .{});
}
const decl = try sema.lookupIdentifier(block, lhs_src, decl_name);
const options = try sema.resolveInstConst(block, rhs_src, extra.options);
const struct_obj = options.ty.castTag(.@"struct").?.data;

11
src/Zir.zig
View File

@@ -347,8 +347,9 @@ pub const Inst = struct {
error_union_type,
/// `error.Foo` syntax. Uses the `str_tok` field of the Data union.
error_value,
/// Implements the `@export` builtin function.
/// Uses the `pl_node` union field. Payload is `Bin`.
/// Implements the `@export` builtin function, based on either an identifier to a Decl,
/// or field access of a Decl.
/// Uses the `pl_node` union field. Payload is `Export`.
@"export",
/// Given a pointer to a struct or object that contains virtual fields, returns a pointer
/// to the named field. The field name is stored in string_bytes. Used by a.b syntax.
@@ -2738,6 +2739,9 @@ pub const Inst = struct {
};
pub const Export = struct {
/// If present, this is referring to a Decl via field access, e.g. `a.b`.
/// If omitted, this is referring to a Decl via identifier, e.g. `a`.
namespace: Ref,
/// Null-terminated string index.
decl_name: u32,
options: Ref,
@@ -3284,7 +3288,8 @@ const Writer = struct {
const extra = self.code.extraData(Inst.Export, inst_data.payload_index).data;
const decl_name = self.code.nullTerminatedString(extra.decl_name);
try stream.print("{}, ", .{std.zig.fmtId(decl_name)});
try self.writeInstRef(stream, extra.namespace);
try stream.print(", {}, ", .{std.zig.fmtId(decl_name)});
try self.writeInstRef(stream, extra.options);
try stream.writeAll(") ");
try self.writeSrc(stream, inst_data.src());