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Disallow compile time bindings where they aren't clearly supported. (#4338)

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This is resolving a fuzz-discovered crash related to function suspends
and compile time bind indices. Although the crash originally came from
clearly invalid syntax (missing the `=` inside a `class` decl), the
syntax with a value should also be valid but has the same crash.

This approach disallows compile-time bindings in contexts that can
create ambiguous results, particularly class declarations. These are an
issue because a suspended function can have let declarations after it.
I'm allowing them in function bodies and interface scopes.

---------

Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This commit is contained in:
Jon Ross-Perkins
2024-09-25 17:06:09 +00:00
committed by GitHub
co-authored by Richard Smith
parent 49a8efbe1b
commit 87678cc374
8 changed files with 946 additions and 281 deletions
Download Patch File Download Diff File Expand all files Collapse all files
toolchain/check/scope_stack.cpp
+16 -14
View File
@@ -13,6 +13,18 @@ auto ScopeStack::VerifyOnFinish() -> void {
CARBON_CHECK(scope_stack_.empty(), "{0}", scope_stack_.size());
}
auto ScopeStack::VerifyNextCompileTimeBindIndex(llvm::StringLiteral label,
const ScopeStackEntry& scope)
-> void {
CARBON_CHECK(
static_cast<int32_t>(compile_time_binding_stack_.all_values_size()) ==
scope.next_compile_time_bind_index.index,
"Wrong number of entries in compile-time binding stack after {0}: have "
"{1}, expected {2}",
label, compile_time_binding_stack_.all_values_size(),
scope.next_compile_time_bind_index.index);
}
auto ScopeStack::Push(SemIR::InstId scope_inst_id, SemIR::NameScopeId scope_id,
SemIR::SpecificId specific_id,
bool lexical_lookup_has_load_error) -> void {
@@ -49,6 +61,8 @@ auto ScopeStack::Push(SemIR::InstId scope_inst_id, SemIR::NameScopeId scope_id,
CARBON_CHECK(next_scope_index_.index != std::numeric_limits<int32_t>::max(),
"Ran out of scopes");
++next_scope_index_.index;
VerifyNextCompileTimeBindIndex("Push", scope_stack_.back());
}
auto ScopeStack::Pop() -> void {
@@ -72,13 +86,7 @@ auto ScopeStack::Pop() -> void {
return_scope_stack_.back().returned_var = SemIR::InstId::Invalid;
}
CARBON_CHECK(
scope.next_compile_time_bind_index.index ==
static_cast<int32_t>(compile_time_binding_stack_.all_values_size()),
"Wrong number of entries in compile-time binding stack, have {0}, "
"expected {1}",
compile_time_binding_stack_.all_values_size(),
scope.next_compile_time_bind_index.index);
VerifyNextCompileTimeBindIndex("Pop", scope);
compile_time_binding_stack_.PopArray();
}
@@ -216,13 +224,7 @@ auto ScopeStack::Restore(SuspendedScope scope) -> void {
}
}
CARBON_CHECK(
scope.entry.next_compile_time_bind_index.index ==
static_cast<int32_t>(compile_time_binding_stack_.all_values_size()),
"Wrong number of entries in compile-time binding stack when restoring, "
"have {0}, expected {1}",
compile_time_binding_stack_.all_values_size(),
scope.entry.next_compile_time_bind_index.index);
VerifyNextCompileTimeBindIndex("Restore", scope.entry);
if (scope.entry.scope_id.is_valid()) {
non_lexical_scope_stack_.push_back(