Swift: added trapgen

This checks in the trapgen script generating trap entries in C++.

The codegen suite has been slightly reorganized, moving the templates
directory up one level and chopping everything into smaller bazel
packages. Running tests is now done via
```
bazel run //swift/codegen/test
```

With respect to the PoC, the nested `codeql::trap` namespace has been
dropped in favour of a `Trap` prefix (or suffix in case of entries)
within the `codeql` namespace. Also, generated C++ code is not checked
in in git any more, and generated during build. Finally, labels get
printed in hex in the trap file.

`TrapLabel` is for the moment only default-constructible, so only one
single label is possible. `TrapArena`, that is responsible for creating
disjoint labels will come in a later commit.

.github/workflows/swift-codegen.yml

@@ -13,18 +13,18 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
+      - uses: ./.github/actions/fetch-codeql
+      - uses: bazelbuild/setup-bazelisk@v2
       - uses: actions/setup-python@v3
         with:
           python-version: '~3.8'
           cache: 'pip'
-      - uses: ./.github/actions/fetch-codeql
-      - uses: bazelbuild/setup-bazelisk@v2
-      - name: Install dependencies
+      - name: Install python dependencies
         run: |
           pip install -r swift/codegen/requirements.txt
       - name: Run unit tests
         run: |
-          bazel test //swift/codegen:tests --test_output=errors
+          bazel test //swift/codegen/test --test_output=errors
       - name: Check that code was generated
         run: |
           bazel run //swift/codegen

.github/workflows/swift-qltest.yml

@@ -29,6 +29,13 @@ jobs:
       - uses: actions/checkout@v3
       - uses: ./.github/actions/fetch-codeql
       - uses: bazelbuild/setup-bazelisk@v2
+      - uses: actions/setup-python@v3
+        with:
+          python-version: '~3.8'
+          cache: 'pip'
+      - name: Install python dependencies
+        run: |
+          pip install -r codegen/requirements.txt
       - name: Build Swift extractor
         run: |
           bazel run //swift:create-extractor-pack

.pre-commit-config.yaml

@@ -47,5 +47,5 @@ repos:
         name: Run Swift code generation unit tests
         files: ^swift/codegen/.*\.py$
         language: system
-        entry: bazel test //swift/codegen:tests
+        entry: bazel test //swift/codegen/test
         pass_filenames: false

swift/.gitignore

@@ -1 +1,5 @@
-extractor-pack
+# directory created by bazel run //swift:create-extractor-pack
+/extractor-pack
+
+# output files created by running tests
+*.o

swift/BUILD.bazel

@@ -2,11 +2,17 @@ load("@rules_pkg//:mappings.bzl", "pkg_attributes", "pkg_filegroup", "pkg_files"
 load("@rules_pkg//:install.bzl", "pkg_install")
 load("//:defs.bzl", "codeql_platform")
 
-pkg_files(
+filegroup(
     name = "dbscheme",
+    srcs = ["ql/lib/swift.dbscheme"],
+    visibility = ["//visibility:public"],
+)
+
+pkg_files(
+    name = "dbscheme_files",
     srcs = [
-        "ql/lib/swift.dbscheme",
         "ql/lib/swift.dbscheme.stats",
+        ":dbscheme",
     ],
 )
 
@@ -25,7 +31,7 @@ pkg_files(
 pkg_filegroup(
     name = "extractor-pack-generic",
     srcs = [
-        ":dbscheme",
+        ":dbscheme_files",
         ":manifest",
         ":qltest",
     ],
@@ -58,7 +64,7 @@ pkg_filegroup(
     name = "extractor-pack-arch",
     srcs = [
         ":extractor",
-        ":swift-test-sdk-arch"
+        ":swift-test-sdk-arch",
     ],
     visibility = ["//visibility:public"],
 )

swift/codegen/BUILD.bazel

@@ -1,31 +1,16 @@
 py_binary(
     name = "codegen",
-    srcs = glob([
-        "lib/*.py",
-        "*.py",
-    ]),
+    srcs = glob(["*.py"]),
+    visibility = ["//swift/codegen/test:__pkg__"],
+    deps = ["//swift/codegen/lib"],
 )
 
-py_library(
-    name = "test_utils",
-    testonly = True,
-    srcs = ["test/utils.py"],
-    deps = [":codegen"],
-)
-
-[
-    py_test(
-        name = src[len("test/"):-len(".py")],
-        size = "small",
-        srcs = [src],
-        deps = [
-            ":codegen",
-            ":test_utils",
-        ],
-    )
-    for src in glob(["test/test_*.py"])
-]
-
-test_suite(
-    name = "tests",
+# as opposed to the above, that is meant to only be run with bazel run,
+# we need to be precise with data dependencies of this which is meant be run during build
+py_binary(
+    name = "trapgen",
+    srcs = ["trapgen.py"],
+    data = ["//swift/codegen/templates:cpp"],
+    visibility = ["//swift:__subpackages__"],
+    deps = ["//swift/codegen/lib"],
 )

swift/codegen/codegen.py

@@ -6,4 +6,4 @@ import dbschemegen
 import qlgen
 
 if __name__ == "__main__":
-    generator.run(dbschemegen.generate, qlgen.generate)
+    generator.run(dbschemegen, qlgen)

swift/codegen/dbschemegen.py

@@ -79,11 +79,13 @@ def generate(opts, renderer):
     data = schema.load(input)
 
     dbscheme = Scheme(src=input.relative_to(paths.swift_dir),
-                        includes=get_includes(data, include_dir=input.parent),
-                        declarations=get_declarations(data))
+                      includes=get_includes(data, include_dir=input.parent),
+                      declarations=get_declarations(data))
 
     renderer.render(dbscheme, out)
 
 
+tags = ("schema", "dbscheme")
+
 if __name__ == "__main__":
-    generator.run(generate, tags=["schema", "dbscheme"])
+    generator.run()

swift/codegen/lib/BUILD.bazel

@@ -0,0 +1,5 @@
+py_library(
+    name = "lib",
+    srcs = glob(["*.py"]),
+    visibility = ["//swift/codegen:__subpackages__"],
+)

swift/codegen/lib/cpp.py

@@ -0,0 +1,83 @@
+from dataclasses import dataclass, field
+from typing import List, ClassVar
+
+# taken from https://en.cppreference.com/w/cpp/keyword
+cpp_keywords = {"alignas", "alignof", "and", "and_eq", "asm", "atomic_cancel", "atomic_commit", "atomic_noexcept",
+                "auto", "bitand", "bitor", "bool", "break", "case", "catch", "char", "char8_t", "char16_t", "char32_t",
+                "class", "compl", "concept", "const", "consteval", "constexpr", "constinit", "const_cast", "continue",
+                "co_await", "co_return", "co_yield", "decltype", "default", "delete", "do", "double", "dynamic_cast",
+                "else", "enum", "explicit", "export", "extern", "false", "float", "for", "friend", "goto", "if",
+                "inline", "int", "long", "mutable", "namespace", "new", "noexcept", "not", "not_eq", "nullptr",
+                "operator", "or", "or_eq", "private", "protected", "public", "reflexpr", "register", "reinterpret_cast",
+                "requires", "return", "short", "signed", "sizeof", "static", "static_assert", "static_cast", "struct",
+                "switch", "synchronized", "template", "this", "thread_local", "throw", "true", "try", "typedef",
+                "typeid", "typename", "union", "unsigned", "using", "virtual", "void", "volatile", "wchar_t", "while",
+                "xor", "xor_eq"}
+
+
+@dataclass
+class Field:
+    name: str
+    type: str
+    first: bool = False
+
+    def cpp_name(self):
+        if self.name in cpp_keywords:
+            return self.name + "_"
+        return self.name
+
+    def stream(self):
+        if self.type == "std::string":
+            return lambda x: f"trapQuoted({x})"
+        elif self.type == "bool":
+            return lambda x: f'({x} ? "true" : "false")'
+        else:
+            return lambda x: x
+
+
+@dataclass
+class Trap:
+    table_name: str
+    name: str
+    fields: List[Field]
+    id: Field = None
+
+    def __post_init__(self):
+        assert self.fields
+        self.fields[0].first = True
+
+
+@dataclass
+class TagBase:
+    base: str
+    first: bool = False
+
+
+@dataclass
+class Tag:
+    name: str
+    bases: List[TagBase]
+    index: int
+    id: str
+
+    def __post_init__(self):
+        if self.bases:
+            self.bases = [TagBase(b) for b in self.bases]
+            self.bases[0].first = True
+
+    def has_bases(self):
+        return bool(self.bases)
+
+
+@dataclass
+class TrapList:
+    template: ClassVar = 'cpp_traps'
+
+    traps: List[Trap] = field(default_factory=list)
+
+
+@dataclass
+class TagList:
+    template: ClassVar = 'cpp_tags'
+
+    tags: List[Tag] = field(default_factory=list)

swift/codegen/lib/dbscheme.py

@@ -1,6 +1,7 @@
 """ dbscheme format representation """
 
 import logging
+import re
 from dataclasses import dataclass
 from typing import ClassVar, List
 
@@ -102,3 +103,54 @@ class Scheme:
     src: str
     includes: List[SchemeInclude]
     declarations: List[Decl]
+
+
+class Re:
+    entity = re.compile(
+        "(?m)"
+        r"(?:^#keyset\[(?P<tablekeys>[\w\s,]+)\][\s\n]*)?^(?P<table>\w+)\((?P<tablebody>[^\)]*)\);?"
+        "|"
+        r"^(?P<union>@\w+)\s*=\s*(?P<unionbody>@\w+(?:\s*\|\s*@\w+)*)\s*;?"
+    )
+    field = re.compile(r"(?m)[\w\s]*\s(?P<field>\w+)\s*:\s*(?P<type>@?\w+)(?P<ref>\s+ref)?")
+    key = re.compile(r"@\w+")
+    comment = re.compile(r"(?m)(?s)/\*.*?\*/|//[^\n]*$")
+
+
+def get_column(match):
+    return Column(
+        schema_name=match["field"].rstrip("_"),
+        type=match["type"],
+        binding=not match["ref"],
+    )
+
+
+def get_table(match):
+    keyset = None
+    if match["tablekeys"]:
+        keyset = KeySet(k.strip() for k in match["tablekeys"].split(","))
+    return Table(
+        name=match["table"],
+        columns=[get_column(f) for f in Re.field.finditer(match["tablebody"])],
+        keyset=keyset,
+    )
+
+
+def get_union(match):
+    return Union(
+        lhs=match["union"],
+        rhs=(d[0] for d in Re.key.finditer(match["unionbody"])),
+    )
+
+
+def iterload(file):
+    data = Re.comment.sub("", file.read())
+    for e in Re.entity.finditer(data):
+        if e["table"]:
+            yield get_table(e)
+        elif e["union"]:
+            yield get_union(e)
+
+
+def load(file):
+    return list(iterload(file))

swift/codegen/lib/generator.py

@@ -17,11 +17,12 @@ def _parse(tags):
     return ret
 
 
-def run(*generators, tags=None):
-    """ run generation functions in `generators`, parsing options tagged with `tags` (all if unspecified)
-
-    `generators` should be callables taking as input an option namespace and a `render.Renderer` instance
+def run(*modules):
+    """ run generation functions in specified in `modules`, or in current module by default
     """
-    opts = _parse(tags)
-    for g in generators:
-        g(opts, render.Renderer())
+    if modules:
+        opts = _parse({t for m in modules for t in m.tags})
+        for m in modules:
+            m.generate(opts, render.Renderer())
+    else:
+        run(sys.modules["__main__"])

swift/codegen/lib/options.py

@@ -3,7 +3,7 @@
 import argparse
 import collections
 import pathlib
-from typing import Tuple
+from typing import Set
 
 from . import paths
 
@@ -15,6 +15,7 @@ def _init_options():
     Option("--ql-output", tags=["ql"], type=_abspath, default=paths.swift_dir / "ql/lib/codeql/swift/generated")
     Option("--ql-stub-output", tags=["ql"], type=_abspath, default=paths.swift_dir / "ql/lib/codeql/swift/elements")
     Option("--codeql-binary", tags=["ql"], default="codeql")
+    Option("--trap-output", tags=["trap"], type=_abspath, required=True)
 
 
 def _abspath(x):
@@ -42,13 +43,10 @@ class Option:
 _init_options()
 
 
-def get(tags: Tuple[str]):
+def get(tags: Set[str]):
     """ get options marked by `tags`
 
-    Return all options if tags is falsy. Options tagged by wildcard '*' are always returned
+    Options tagged by wildcard '*' are always returned
     """
-    if not tags:
-        return (o for tagged_opts in _options.values() for o in tagged_opts)
-    else:
-        # use specifically tagged options + those tagged with wildcard *
-        return (o for tag in ('*',) + tags for o in _options[tag])
+    # use specifically tagged options + those tagged with wildcard *
+    return (o for tag in ('*',) + tuple(tags) for o in _options[tag])

swift/codegen/lib/paths.py

@@ -5,14 +5,15 @@ import sys
 import os
 
 try:
-    _workspace_dir = pathlib.Path(os.environ['BUILD_WORKSPACE_DIRECTORY']).resolve()  # <- means we are using bazel run
-    swift_dir = _workspace_dir / 'swift'
+    workspace_dir = pathlib.Path(os.environ['BUILD_WORKSPACE_DIRECTORY']).resolve()  # <- means we are using bazel run
+    swift_dir = workspace_dir / 'swift'
 except KeyError:
     _this_file = pathlib.Path(__file__).resolve()
     swift_dir = _this_file.parents[2]
+    workspace_dir = swift_dir.parent
 
 lib_dir = swift_dir / 'codegen' / 'lib'
-templates_dir = lib_dir / 'templates'
+templates_dir = swift_dir / 'codegen' / 'templates'
 
 try:
     exe_file = pathlib.Path(sys.argv[0]).resolve().relative_to(swift_dir)

swift/codegen/lib/render.py

@@ -19,19 +19,25 @@ class Renderer:
     """ Template renderer using mustache templates in the `templates` directory """
 
     def __init__(self):
-        self._r = pystache.Renderer(search_dirs=str(paths.lib_dir / "templates"), escape=lambda u: u)
+        self._r = pystache.Renderer(search_dirs=str(paths.templates_dir), escape=lambda u: u)
         self.written = set()
 
-    def render(self, data, output: pathlib.Path):
+    def render(self, data, output: pathlib.Path, guard_base: pathlib.Path = None):
         """ Render `data` to `output`.
 
         `data` must have a `template` attribute denoting which template to use from the template directory.
 
         If the file is unchanged, then no write is performed (and `done_something` remains unchanged)
+
+        If `guard_base` is provided, it must be a path at the root of `output` and a header guard will be injected in
+        the template based off of the relative path of `output` in `guard_base`
         """
         mnemonic = type(data).__name__
         output.parent.mkdir(parents=True, exist_ok=True)
-        data = self._r.render_name(data.template, data, generator=paths.exe_file)
+        guard = None
+        if guard_base is not None:
+            guard = str(output.relative_to(guard_base)).replace("/", "_").replace(".", "_").upper()
+        data = self._r.render_name(data.template, data, generator=paths.exe_file, guard=guard)
         with open(output, "w") as out:
             out.write(data)
         log.debug(f"generated {mnemonic} {output.name}")

swift/codegen/qlgen.py

@@ -110,5 +110,7 @@ def generate(opts, renderer):
     format(opts.codeql_binary, renderer.written)
 
 
+tags = ("schema", "ql")
+
 if __name__ == "__main__":
-    generator.run(generate, tags=["schema", "ql"])
+    generator.run()

swift/codegen/templates/BUILD.bazel

@@ -0,0 +1,5 @@
+filegroup(
+    name = "cpp",
+    srcs = glob(["cpp_*.mustache"]),
+    visibility = ["//swift:__subpackages__"],
+)

swift/codegen/templates/cpp_tags.mustache

@@ -0,0 +1,15 @@
+// generated by {{generator}}
+// clang-format off
+#ifndef SWIFT_EXTRACTOR_TRAP_{{guard}}
+#define SWIFT_EXTRACTOR_TRAP_{{guard}}
+
+namespace codeql {
+{{#tags}}
+
+// {{id}}
+struct {{name}}Tag {{#has_bases}}: {{#bases}}{{^first}}, {{/first}}{{base}}Tag{{/bases}} {{/has_bases}}{
+  static constexpr const char* prefix = "{{index}}";
+};
+{{/tags}}
+}
+#endif

swift/codegen/templates/cpp_traps.mustache

@@ -0,0 +1,35 @@
+// generated by {{generator}}
+// clang-format off
+#ifndef SWIFT_EXTRACTOR_TRAP_{{guard}}
+#define SWIFT_EXTRACTOR_TRAP_{{guard}}
+
+#include <iostream>
+#include <string>
+
+#include "swift/extractor/trap/TrapLabel.h"
+#include "swift/extractor/trap/TrapTags.h"
+
+namespace codeql {
+{{#traps}}
+
+// {{table_name}}
+struct {{name}}Trap {
+  static constexpr bool is_binding = {{#id}}true{{/id}}{{^id}}false{{/id}};
+{{#id}}
+  {{type}} getBoundLabel() const { return {{cpp_name}}; }
+{{/id}}
+
+{{#fields}}
+  {{type}} {{cpp_name}}{};
+{{/fields}}
+};
+
+inline std::ostream &operator<<(std::ostream &out, const {{name}}Trap &e) {
+  out << "{{table_name}}("{{#fields}}{{^first}} << ", "{{/first}}
+      << {{#stream}}e.{{cpp_name}}{{/stream}}{{/fields}} << ")";
+  return out;
+}
+{{/traps}}
+
+}
+#endif

swift/codegen/test/BUILD.bazel

@@ -0,0 +1,23 @@
+py_library(
+    name = "utils",
+    testonly = True,
+    srcs = ["utils.py"],
+    deps = ["//swift/codegen/lib"],
+)
+
+[
+    py_test(
+        name = src[:-len(".py")],
+        size = "small",
+        srcs = [src],
+        deps = [
+            ":utils",
+            "//swift/codegen",
+        ],
+    )
+    for src in glob(["test_*.py"])
+]
+
+test_suite(
+    name = "test",
+)

swift/codegen/test/test_render.py

@@ -1,4 +1,5 @@
 import sys
+import pathlib
 from unittest import mock
 
 import pytest
@@ -40,8 +41,8 @@ def test_render(pystache_renderer, sut):
     with mock.patch("builtins.open", mock.mock_open()) as output_stream:
         sut.render(data, output)
     assert pystache_renderer.mock_calls == [
-        mock.call.render_name(data.template, data, generator=paths.exe_file),
-    ], pystache_renderer.mock_calls
+        mock.call.render_name(data.template, data, generator=paths.exe_file, guard=None),
+    ]
     assert output_stream.mock_calls == [
         mock.call(output, 'w'),
         mock.call().__enter__(),
@@ -51,6 +52,17 @@ def test_render(pystache_renderer, sut):
     assert sut.written == {output}
 
 
+def test_render_with_guard(pystache_renderer, sut):
+    guard_base = pathlib.Path("test", "guard")
+    data = mock.Mock()
+    output = guard_base / "this" / "is" / "a" / "header.h"
+    with mock.patch("builtins.open", mock.mock_open()) as output_stream:
+        sut.render(data, output, guard_base=guard_base)
+    assert pystache_renderer.mock_calls == [
+        mock.call.render_name(data.template, data, generator=paths.exe_file, guard="THIS_IS_A_HEADER_H"),
+    ]
+
+
 def test_written(sut):
     data = [mock.Mock() for _ in range(4)]
     output = [mock.Mock() for _ in data]

swift/codegen/trapgen.py

@@ -0,0 +1,136 @@
+#!/usr/bin/env python3
+
+import collections
+import logging
+import os
+import re
+import sys
+
+import inflection
+
+sys.path.append(os.path.dirname(__file__))
+
+from lib import paths, dbscheme, generator, cpp
+
+field_overrides = [
+    (re.compile(r"locations.*::(start|end).*|.*::(index|num_.*)"), {"type": "unsigned"}),
+    (re.compile(r".*::(.*)_"), lambda m: {"name": m[1]}),
+]
+
+log = logging.getLogger(__name__)
+
+
+def get_field_override(table, field):
+    spec = f"{table}::{field}"
+    for r, o in field_overrides:
+        m = r.fullmatch(spec)
+        if m and callable(o):
+            return o(m)
+        elif m:
+            return o
+    return {}
+
+
+def get_tag_name(s):
+    assert s.startswith("@")
+    return inflection.camelize(s[1:])
+
+
+def get_cpp_type(schema_type):
+    if schema_type.startswith("@"):
+        tag = get_tag_name(schema_type)
+        return f"TrapLabel<{tag}Tag>"
+    if schema_type == "string":
+        return "std::string"
+    if schema_type == "boolean":
+        return "bool"
+    return schema_type
+
+
+def get_field(c: dbscheme.Column, table: str):
+    args = {
+        "name": c.schema_name,
+        "type": c.type,
+    }
+    args.update(get_field_override(table, c.schema_name))
+    args["type"] = get_cpp_type(args["type"])
+    return cpp.Field(**args)
+
+
+def get_binding_column(t: dbscheme.Table):
+    try:
+        return next(c for c in t.columns if c.binding)
+    except StopIteration:
+        return None
+
+
+def get_trap(t: dbscheme.Table):
+    id = get_binding_column(t)
+    if id:
+        id = get_field(id, t.name)
+    return cpp.Trap(
+        table_name=t.name,
+        name=inflection.camelize(t.name),
+        fields=[get_field(c, t.name) for c in t.columns],
+        id=id,
+    )
+
+
+def get_guard(path):
+    path = path.relative_to(paths.swift_dir)
+    return str(path.with_suffix("")).replace("/", "_").upper()
+
+
+def get_topologically_ordered_tags(tags):
+    degree_to_nodes = collections.defaultdict(set)
+    nodes_to_degree = {}
+    lookup = {}
+    for name, t in tags.items():
+        degree = len(t["bases"])
+        degree_to_nodes[degree].add(name)
+        nodes_to_degree[name] = degree
+    while degree_to_nodes[0]:
+        sinks = degree_to_nodes.pop(0)
+        for sink in sorted(sinks):
+            yield sink
+            for d in tags[sink]["derived"]:
+                degree = nodes_to_degree[d]
+                degree_to_nodes[degree].remove(d)
+                degree -= 1
+                nodes_to_degree[d] = degree
+                degree_to_nodes[degree].add(d)
+    if any(degree_to_nodes.values()):
+        raise ValueError("not a dag!")
+
+
+def generate(opts, renderer):
+    tag_graph = collections.defaultdict(lambda: {"bases": [], "derived": []})
+    out = opts.trap_output
+
+    traps = []
+    with open(opts.dbscheme) as input:
+        for e in dbscheme.iterload(input):
+            if e.is_table:
+                traps.append(get_trap(e))
+            elif e.is_union:
+                for d in e.rhs:
+                    tag_graph[e.lhs]["derived"].append(d.type)
+                    tag_graph[d.type]["bases"].append(e.lhs)
+
+    renderer.render(cpp.TrapList(traps), out / "TrapEntries.h", guard_base=out)
+
+    tags = []
+    for index, tag in enumerate(get_topologically_ordered_tags(tag_graph)):
+        tags.append(cpp.Tag(
+            name=get_tag_name(tag),
+            bases=[get_tag_name(b) for b in sorted(tag_graph[tag]["bases"])],
+            index=index,
+            id=tag,
+        ))
+    renderer.render(cpp.TagList(tags), out / "TrapTags.h", guard_base=out)
+
+
+tags = ("trap", "dbscheme")
+
+if __name__ == "__main__":
+    generator.run()

swift/extractor/BUILD.bazel

@@ -9,17 +9,20 @@ alias(
 cc_binary(
     name = "extractor",
     srcs = [
-        "SwiftExtractor.h",
         "SwiftExtractor.cpp",
+        "SwiftExtractor.h",
         "SwiftExtractorConfiguration.h",
         "main.cpp",
     ],
+    features = ["-universal_binaries"],
     target_compatible_with = select({
         "@platforms//os:linux": [],
         "@platforms//os:macos": [],
         "//conditions:default": ["@platforms//:incompatible"],
     }),
     visibility = ["//swift:__pkg__"],
-    deps = [":swift-llvm-support"],
-    features = ["-universal_binaries"],
+    deps = [
+        ":swift-llvm-support",
+        "//swift/extractor/trap",
+    ],
 )

swift/extractor/SwiftExtractor.cpp

@@ -12,6 +12,8 @@
 #include <llvm/Support/FileSystem.h>
 #include <llvm/Support/Path.h>
 
+#include "swift/extractor/trap/TrapEntries.h"
+
 using namespace codeql;
 
 static void extractFile(const SwiftExtractorConfiguration& config, swift::SourceFile& file) {
@@ -60,15 +62,15 @@ static void extractFile(const SwiftExtractorConfiguration& config, swift::Source
               << "': " << ec.message() << "\n";
     return;
   }
-  std::stringstream ss;
+  trap << "// extractor-args: ";
   for (auto opt : config.frontendOptions) {
-    ss << std::quoted(opt) << " ";
+    trap << std::quoted(opt) << " ";
   }
-  ss << "\n";
-  trap << "// extractor-args: " << ss.str();
+  trap << "\n\n";
 
-  trap << "#0=*\n";
-  trap << "files(#0, " << std::quoted(srcFilePath.str().str()) << ")\n";
+  TrapLabel<FileTag> label{};
+  trap << label << "=*\n";
+  trap << FilesTrap{label, srcFilePath.str().str()} << "\n";
 
   // TODO: Pick a better name to avoid collisions
   std::string trapName = file.getFilename().str() + ".trap";

swift/extractor/trap/BUILD.bazel

@@ -0,0 +1,16 @@
+genrule(
+    name = "gen",
+    srcs = ["//swift:dbscheme"],
+    outs = [
+        "TrapEntries.h",
+        "TrapTags.h",
+    ],
+    cmd = "$(location //swift/codegen:trapgen) --dbscheme $< --trap-output $(RULEDIR)",
+    exec_tools = ["//swift/codegen:trapgen"],
+)
+
+cc_library(
+    name = "trap",
+    hdrs = glob(["*.h"]) + [":gen"],
+    visibility = ["//visibility:public"],
+)

swift/extractor/trap/TrapLabel.h

@@ -0,0 +1,68 @@
+#ifndef SWIFT_EXTRACTOR_TRAP_LABEL_H
+#define SWIFT_EXTRACTOR_TRAP_LABEL_H
+
+#include <iomanip>
+#include <iostream>
+#include <string>
+
+#include "swift/extractor/trap/TrapTagTraits.h"
+#include "swift/extractor/trap/TrapTags.h"
+
+namespace codeql {
+
+class UntypedTrapLabel {
+  uint64_t id_;
+
+  friend class std::hash<UntypedTrapLabel>;
+
+ protected:
+  UntypedTrapLabel() : id_{0xffffffffffffffff} {}
+  UntypedTrapLabel(uint64_t id) : id_{id} {}
+
+ public:
+  friend std::ostream& operator<<(std::ostream& out, UntypedTrapLabel l) {
+    out << '#' << std::hex << l.id_ << std::dec;
+    return out;
+  }
+
+  friend bool operator==(UntypedTrapLabel lhs, UntypedTrapLabel rhs) { return lhs.id_ == rhs.id_; }
+};
+
+template <typename Tag>
+class TrapLabel : public UntypedTrapLabel {
+  template <typename OtherTag>
+  friend class TrapLabel;
+
+  using UntypedTrapLabel::UntypedTrapLabel;
+
+ public:
+  TrapLabel() = default;
+
+  template <typename OtherTag>
+  TrapLabel(const TrapLabel<OtherTag>& other) : UntypedTrapLabel(other) {
+    // we temporarily need to bypass the label type system for unknown AST nodes and types
+    if constexpr (std::is_same_v<Tag, UnknownAstNodeTag>) {
+      static_assert(std::is_base_of_v<AstNodeTag, OtherTag>, "wrong label assignment!");
+    } else if constexpr (std::is_same_v<Tag, UnknownTypeTag>) {
+      static_assert(std::is_base_of_v<TypeTag, OtherTag>, "wrong label assignment!");
+    } else {
+      static_assert(std::is_base_of_v<Tag, OtherTag>, "wrong label assignment!");
+    }
+  }
+};
+
+inline auto trapQuoted(const std::string& s) {
+  return std::quoted(s, '"', '"');
+}
+
+}  // namespace codeql
+
+namespace std {
+template <>
+struct hash<codeql::UntypedTrapLabel> {
+  size_t operator()(const codeql::UntypedTrapLabel& l) const noexcept {
+    return std::hash<uint64_t>{}(l.id_);
+  }
+};
+}  // namespace std
+#endif  // SWIFT_EXTRACTOR_LIB_EXTRACTOR_CPP_TRAP_LABEL_H_

swift/extractor/trap/TrapTagTraits.h

@@ -0,0 +1,18 @@
+#ifndef SWIFT_EXTRACTOR_INCLUDE_EXTRACTOR_TRAP_TAGTRAITS_H
+#define SWIFT_EXTRACTOR_INCLUDE_EXTRACTOR_TRAP_TAGTRAITS_H
+
+#include <type_traits>
+
+namespace codeql::trap {
+
+template <typename T>
+struct ToTagFunctor;
+template <typename T>
+struct ToTagOverride : ToTagFunctor<T> {};
+
+template <typename T>
+using ToTag = typename ToTagOverride<std::remove_const_t<T>>::type;
+
+}  // namespace codeql::trap
+
+#endif  // SWIFT_EXTRACTOR_INCLUDE_EXTRACTOR_TRAP_TAGTRAITS_H