Generate thunks for functions in impls (#5390)

Generate a thunk when a function in an `impl` has a different signature than the function in the interface. This follows the design in [#3763](https://docs.carbon-lang.dev/proposals/p3763.html#impl-members-vs-interface-members), although some of the checks described there are not yet implemented. --------- Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
2026-10-05 22:02:55 +01:00 · 2025-05-01 22:17:55 +00:00
parent 4f5d11a28b
commit 95903dc624
31 changed files with 3438 additions and 710 deletions
@@ -0,0 +1,99 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include "toolchain/check/pattern.h"
+
+#include "toolchain/check/inst.h"
+#include "toolchain/check/type.h"
+
+namespace Carbon::Check {
+
+auto BeginSubpattern(Context& context) -> void {
+  context.inst_block_stack().Push();
+  context.region_stack().PushRegion(context.inst_block_stack().PeekOrAdd());
+}
+
+auto EndSubpatternAsExpr(Context& context, SemIR::InstId result_id)
+    -> SemIR::ExprRegionId {
+  if (context.region_stack().PeekRegion().size() > 1) {
+    // End the exit block with a branch to a successor block, whose contents
+    // will be determined later.
+    AddInst(context,
+            SemIR::LocIdAndInst::NoLoc<SemIR::Branch>(
+                {.target_id = context.inst_blocks().AddPlaceholder()}));
+  } else {
+    // This single-block region will be inserted as a SpliceBlock, so we don't
+    // need control flow out of it.
+  }
+  auto block_id = context.inst_block_stack().Pop();
+  CARBON_CHECK(block_id == context.region_stack().PeekRegion().back());
+
+  // TODO: Is it possible to validate that this region is genuinely
+  // single-entry, single-exit?
+  return context.sem_ir().expr_regions().Add(
+      {.block_ids = context.region_stack().PopRegion(),
+       .result_id = result_id});
+}
+
+auto EndSubpatternAsNonExpr(Context& context) -> void {
+  auto block_id = context.inst_block_stack().Pop();
+  CARBON_CHECK(block_id == context.region_stack().PeekRegion().back());
+  CARBON_CHECK(context.region_stack().PeekRegion().size() == 1);
+  // TODO: Add `CARBON_CHECK(inst_blocks().Get(block_id).empty())`.
+  // Currently that can fail when ending a tuple pattern in a name binding
+  // decl in a class or interface.
+  context.region_stack().PopAndDiscardRegion();
+}
+
+auto AddBindingPattern(Context& context, SemIR::LocId name_loc,
+                       SemIR::NameId name_id, SemIR::TypeId type_id,
+                       SemIR::ExprRegionId type_region_id, bool is_generic,
+                       bool is_template) -> BindingPatternInfo {
+  auto entity_name_id = context.entity_names().AddSymbolicBindingName(
+      name_id, context.scope_stack().PeekNameScopeId(),
+      is_generic ? context.scope_stack().AddCompileTimeBinding()
+                 : SemIR::CompileTimeBindIndex::None,
+      is_template);
+
+  auto bind_id = SemIR::InstId::None;
+  if (is_generic) {
+    bind_id = AddInstInNoBlock<SemIR::BindSymbolicName>(
+        context, name_loc,
+        {.type_id = type_id,
+         .entity_name_id = entity_name_id,
+         .value_id = SemIR::InstId::None});
+  } else {
+    bind_id =
+        AddInstInNoBlock<SemIR::BindName>(context, name_loc,
+                                          {.type_id = type_id,
+                                           .entity_name_id = entity_name_id,
+                                           .value_id = SemIR::InstId::None});
+  }
+
+  auto pattern_type_id = GetPatternType(context, type_id);
+  auto binding_pattern_id = SemIR::InstId::None;
+  if (is_generic) {
+    binding_pattern_id = AddPatternInst<SemIR::SymbolicBindingPattern>(
+        context, name_loc,
+        {.type_id = pattern_type_id, .entity_name_id = entity_name_id});
+  } else {
+    binding_pattern_id = AddPatternInst<SemIR::BindingPattern>(
+        context, name_loc,
+        {.type_id = pattern_type_id, .entity_name_id = entity_name_id});
+  }
+
+  if (is_generic) {
+    context.scope_stack().PushCompileTimeBinding(bind_id);
+  }
+
+  bool inserted =
+      context.bind_name_map()
+          .Insert(binding_pattern_id, {.bind_name_id = bind_id,
+                                       .type_expr_region_id = type_region_id})
+          .is_inserted();
+  CARBON_CHECK(inserted);
+  return {.pattern_id = binding_pattern_id, .bind_id = bind_id};
+}
+
+}  // namespace Carbon::Check