Skip to content

Allow keywords as identifiers in extern(C) blocks for better C interopability #530

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
bangbangsheshotmedown wants to merge 5 commits into
base: master
Choose a base branch
from
Open

Allow keywords as identifiers in extern(C) blocks for better C interopability #530

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
594ac83
Allow keywords as identifiers in extern(C) blocks for ImportC compati…
bangbangsheshotmedown Feb 28, 2026
42e6a74
Allow keywords as identifiers in function parameters
bangbangsheshotmedown Mar 1, 2026
eb198fe
Add tests
bangbangsheshotmedown Mar 1, 2026
0740122
Fix build
bangbangsheshotmedown Mar 1, 2026
b7fc40e
Fix indentation
bangbangsheshotmedown Apr 11, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
75 changes: 56 additions & 19 deletions src/dparse/parser.d
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -118,6 +118,16 @@ Module parseModule(F)(const(Token)[] tokens, string fileName, RollbackAllocator*
*/
class Parser
{
/// Is it a interface file for a C source code
bool importC;
/// Depth of extern(C) blocks we're currently inside
int externCDepth;

bool isInExternC() const pure nothrow @safe @nogc
{
return importC || externCDepth > 0;
}

/**
* Parses an AddExpression.
*
Expand Down Expand Up @@ -2294,26 +2304,43 @@ class Parser
advance();
break;
case tok!"{":
if (node.attributes.empty)
if (node.attributes.empty)
{
error("declaration expected instead of `{`");
return null;
}
// Check if we're in an extern(C) block
bool isExternC = false;
foreach (attr; node.attributes)
{
if (attr.linkageAttribute !is null &&
attr.linkageAttribute.identifier.text == "C")
{
error("declaration expected instead of `{`");
return null;
isExternC = true;
break;
}
advance();
alias declarations = attributes;
declarations.clear();
while (moreTokens() && !currentIs(tok!"}"))
}
if (isExternC)
externCDepth++;
advance();
alias declarations = attributes;
declarations.clear();
while (moreTokens() && !currentIs(tok!"}"))
{
auto c = allocator.setCheckpoint();
if (!declarations.put(parseDeclaration(strict, false, inTemplateDeclaration)))
{
auto c = allocator.setCheckpoint();
if (!declarations.put(parseDeclaration(strict, false, inTemplateDeclaration)))
{
allocator.rollback(c);
return null;
}
allocator.rollback(c);
if (isExternC)
Copy link
Copy Markdown
Member

@WebFreak001 WebFreak001 May 10, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

use scope (exit) instead of duplicating the if (isExternC) externCDepth--; at both exit points

externCDepth--;
return null;
}
ownArray(node.declarations, declarations);
mixin(tokenCheck!"}");
break;
}
if (isExternC)
externCDepth--;
ownArray(node.declarations, declarations);
mixin(tokenCheck!"}");
break;
case tok!"alias":
if (startsWith(tok!"alias", tok!"identifier", tok!"this"))
mixin(parseNodeQ!(`node.aliasThisDeclaration`, `AliasThisDeclaration`));
Expand Down Expand Up @@ -2481,7 +2508,7 @@ class Parser
foreach (B; BasicTypes) { case B: }
type:
Type t = parseType();
if (t is null || !currentIsOneOf(tok!"identifier", tok!":"))
if (t is null || !(currentIs(tok!"identifier") || (isInExternC() && isKeyword(current.type)) || currentIs(tok!":")))
Copy link
Copy Markdown
Member

@WebFreak001 WebFreak001 May 10, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

we should probably not allow all keywords, only what is allowed in C context (e.g. we need a new helper function instead of isKeyword something like isCIdentifier()

{
if (t)
error("no identifier for declarator");
Expand Down Expand Up @@ -2654,7 +2681,17 @@ class Parser
}
else
{
const id = expect(tok!"identifier");
const(Token)* id;
if (currentIs(tok!"identifier") || (isInExternC() && isKeyword(current.type)))
id = &tokens[index++];
else
{
error("Expected identifier instead of " ~ (index < tokens.length
? (tokens[index].text is null ? "`" ~ str(tokens[index].type) ~ "`"
: str(tokens[index].type) ~ " `" ~ tokens[index].text ~ "`")
: "EOF"));
return null;
}
mixin (nullCheck!`id`);
node.name = *id;
Copy link
Copy Markdown
Member

@WebFreak001 WebFreak001 May 10, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

we need a conversion from keyword token to identifier token here, so that node.name.text is set (otherwise it's unset for keywords iirc)

if (currentIs(tok!"[")) // dmd doesn't accept pointer after identifier
Expand Down Expand Up @@ -5495,7 +5532,7 @@ class Parser

ownArray(node.parameterAttributes, parameterAttributes);
mixin(parseNodeQ!(`node.type`, `Type`));
if (currentIs(tok!"identifier"))
if (currentIs(tok!"identifier") || (isInExternC() && isKeyword(current.type)))
{
node.name = advance();
Copy link
Copy Markdown
Member

@WebFreak001 WebFreak001 May 10, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

we need a conversion from keyword token to identifier token here, so that node.name.text is set (otherwise it's unset for keywords iirc)

if (currentIs(tok!"..."))
Expand Down
85 changes: 57 additions & 28 deletions test/tester.d
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -313,34 +313,63 @@ void testArbitraryASTs()
parser.messageDelegate = &msgDelegate;
parser.allocator = &rba;

parser.tokens = getTokensForParser("struct S {}", config, &cache);
assert(parser.parseCompileCondition() is null);
assert(errors == ["`version`, `debug`, or `static` expected (found token `struct`)"]);
errors = null;

parser = new Parser();
parser.messageDelegate = &msgDelegate;
parser.allocator = &rba;
parser.tokens = getTokensForParser("~", config, &cache);
assert(parser.parseDestructor() is null);
assert(errors == ["`this` expected instead of EOF"]);
errors = null;

parser = new Parser();
parser.messageDelegate = &msgDelegate;
parser.allocator = &rba;
parser.tokens = getTokensForParser("for (x; y; z) {}", config, &cache);
assert(parser.parseForeach() is null);
assert(errors == ["`foreach` or `foreach_reverse` expected (found token `for`)"]);
errors = null;

parser = new Parser();
parser.messageDelegate = &msgDelegate;
parser.allocator = &rba;
parser.tokens = getTokensForParser("version =", config, &cache);
assert(parser.parseVersionSpecification() is null);
assert(errors == ["Identifier or integer literal expected (found EOF)"]);
errors = null;
{
parser.tokens = getTokensForParser("struct S {}", config, &cache);
assert(parser.parseCompileCondition() is null);
assert(errors == ["`version`, `debug`, or `static` expected (found token `struct`)"]);
errors = null;
}
{
parser = new Parser();
parser.messageDelegate = &msgDelegate;
parser.allocator = &rba;
parser.tokens = getTokensForParser("~", config, &cache);
assert(parser.parseDestructor() is null);
assert(errors == ["`this` expected instead of EOF"]);
errors = null;
}
{
parser = new Parser();
parser.messageDelegate = &msgDelegate;
parser.allocator = &rba;
parser.tokens = getTokensForParser("for (x; y; z) {}", config, &cache);
assert(parser.parseForeach() is null);
assert(errors == ["`foreach` or `foreach_reverse` expected (found token `for`)"]);
errors = null;
}
{
parser = new Parser();
parser.messageDelegate = &msgDelegate;
parser.allocator = &rba;
parser.tokens = getTokensForParser("version =", config, &cache);
assert(parser.parseVersionSpecification() is null);
assert(errors == ["Identifier or integer literal expected (found EOF)"]);
errors = null;
}
{
parser = new Parser();
parser.messageDelegate = &msgDelegate;
parser.allocator = &rba;
parser.importC = false;
parser.tokens = getTokensForParser("extern(C) { int normal = 1; int true = 1; }", config, &cache);
assert(parser.parseAttribute() !is null);
auto b = parser.parseBlockStatement();
assert(b !is null);
assert(b.declarationsAndStatements.declarationsAndStatements.length == 1);
Copy link
Copy Markdown
Member

@WebFreak001 WebFreak001 May 10, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

please add an assert for the errors array here

errors = null;
}
{
parser = new Parser();
parser.messageDelegate = &msgDelegate;
parser.allocator = &rba;
parser.importC = true;
parser.tokens = getTokensForParser("extern(C) { int normal = 1; int true = 1; }", config, &cache);
assert(parser.parseAttribute() !is null);
auto b = parser.parseBlockStatement();
assert(b !is null);
assert(b.declarationsAndStatements.declarationsAndStatements.length == 2);
errors = null;
}

}

Expand Down
Loading