Handle arrow operator (carbon-language#3768)

This change implements the check behavior for the arrow operator. `ptr->Foo()` is rewritten as `(*ptr).Foo()` and `ptr->(X.y)` is rewritten as `(*ptr).(X.y)`
CJ-Johnson · Mar 18, 2024 · d0e8afc · d0e8afc
1 parent 4421a75
commit d0e8afc
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Showing 17 changed files with 365 additions and 89 deletions.
diff --git a/toolchain/check/BUILD b/toolchain/check/BUILD
@@ -107,6 +107,7 @@ cc_library(
         ":import",
         ":interface",
         ":member_access",
+        ":pointer_dereference",
         "//common:check",
         "//common:ostream",
         "//toolchain/base:pretty_stack_trace_function",
@@ -212,6 +213,21 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "pointer_dereference",
+    srcs = ["pointer_dereference.cpp"],
+    hdrs = ["pointer_dereference.h"],
+    deps = [
+        ":context",
+        "//common:check",
+        "//toolchain/parse:node_kind",
+        "//toolchain/sem_ir:ids",
+        "//toolchain/sem_ir:inst",
+        "//toolchain/sem_ir:inst_kind",
+        "@llvm-project//llvm:Support",
+    ],
+)
+
 cc_library(
     name = "subst",
     srcs = ["subst.cpp"],

diff --git a/toolchain/check/handle_name.cpp b/toolchain/check/handle_name.cpp
@@ -4,8 +4,8 @@
 
 #include "toolchain/check/context.h"
 #include "toolchain/check/member_access.h"
+#include "toolchain/check/pointer_dereference.h"
 #include "toolchain/lex/token_kind.h"
-#include "toolchain/parse/typed_nodes.h"
 #include "toolchain/sem_ir/inst.h"
 #include "toolchain/sem_ir/typed_insts.h"
 
@@ -31,7 +31,36 @@ auto HandleMemberAccessExpr(Context& context, Parse::MemberAccessExprId node_id)
 auto HandlePointerMemberAccessExpr(Context& context,
                                    Parse::PointerMemberAccessExprId node_id)
     -> bool {
-  return context.TODO(node_id, "HandlePointerMemberAccessExpr");
+  auto diagnose_not_pointer = [&context,
+                               &node_id](SemIR::TypeId not_pointer_type_id) {
+    CARBON_DIAGNOSTIC(ArrowOperatorOfNonPointer, Error,
+                      "Cannot apply `->` operator to non-pointer type `{0}`.",
+                      SemIR::TypeId);
+
+    auto builder = context.emitter().Build(
+        TokenOnly(node_id), ArrowOperatorOfNonPointer, not_pointer_type_id);
+    builder.Emit();
+  };
+
+  if (context.node_stack().PeekIs<Parse::NodeKind::ParenExpr>()) {
+    auto member_expr_id = context.node_stack().PopExpr();
+    auto base_id = context.node_stack().PopExpr();
+    auto deref_base_id = PerformPointerDereference(context, node_id, base_id,
+                                                   diagnose_not_pointer);
+    auto member_id = PerformCompoundMemberAccess(context, node_id,
+                                                 deref_base_id, member_expr_id);
+    context.node_stack().Push(node_id, member_id);
+  } else {
+    SemIR::NameId name_id = context.node_stack().PopName();
+    auto base_id = context.node_stack().PopExpr();
+    auto deref_base_id = PerformPointerDereference(context, node_id, base_id,
+                                                   diagnose_not_pointer);
+    auto member_id =
+        PerformMemberAccess(context, node_id, deref_base_id, name_id);
+    context.node_stack().Push(node_id, member_id);
+  }
+
+  return true;
 }
 
 static auto GetIdentifierAsName(Context& context, Parse::NodeId node_id)

diff --git a/toolchain/check/handle_operator.cpp b/toolchain/check/handle_operator.cpp
@@ -4,6 +4,8 @@
 
 #include "toolchain/check/context.h"
 #include "toolchain/check/convert.h"
+#include "toolchain/check/pointer_dereference.h"
+#include "toolchain/diagnostics/diagnostic_emitter.h"
 
 namespace Carbon::Check {
 
@@ -281,30 +283,31 @@ auto HandlePrefixOperatorPlusPlus(Context& context,
 
 auto HandlePrefixOperatorStar(Context& context,
                               Parse::PrefixOperatorStarId node_id) -> bool {
-  auto value_id = context.node_stack().PopExpr();
-  value_id = ConvertToValueExpr(context, value_id);
-  auto type_id =
-      context.GetUnqualifiedType(context.insts().Get(value_id).type_id());
-  auto result_type_id = SemIR::TypeId::Error;
-  if (auto pointer_type =
-          context.types().TryGetAs<SemIR::PointerType>(type_id)) {
-    result_type_id = pointer_type->pointee_id;
-  } else if (type_id != SemIR::TypeId::Error) {
-    CARBON_DIAGNOSTIC(DerefOfNonPointer, Error,
-                      "Cannot dereference operand of non-pointer type `{0}`.",
-                      SemIR::TypeId);
-    auto builder =
-        context.emitter().Build(TokenOnly(node_id), DerefOfNonPointer, type_id);
-    // TODO: Check for any facet here, rather than only a type.
-    if (type_id == SemIR::TypeId::TypeType) {
-      CARBON_DIAGNOSTIC(
-          DerefOfType, Note,
-          "To form a pointer type, write the `*` after the pointee type.");
-      builder.Note(TokenOnly(node_id), DerefOfType);
-    }
-    builder.Emit();
-  }
-  context.AddInstAndPush({node_id, SemIR::Deref{result_type_id, value_id}});
+  auto base_id = context.node_stack().PopExpr();
+
+  auto deref_base_id = PerformPointerDereference(
+      context, node_id, base_id,
+      [&context, &node_id](SemIR::TypeId not_pointer_type_id) {
+        CARBON_DIAGNOSTIC(
+            DerefOfNonPointer, Error,
+            "Cannot dereference operand of non-pointer type `{0}`.",
+            SemIR::TypeId);
+
+        auto builder = context.emitter().Build(
+            TokenOnly(node_id), DerefOfNonPointer, not_pointer_type_id);
+
+        // TODO: Check for any facet here, rather than only a type.
+        if (not_pointer_type_id == SemIR::TypeId::TypeType) {
+          CARBON_DIAGNOSTIC(
+              DerefOfType, Note,
+              "To form a pointer type, write the `*` after the pointee type.");
+          builder.Note(TokenOnly(node_id), DerefOfType);
+        }
+
+        builder.Emit();
+      });
+
+  context.node_stack().Push(node_id, deref_base_id);
   return true;
 }
 

diff --git a/toolchain/check/member_access.cpp b/toolchain/check/member_access.cpp
@@ -195,7 +195,7 @@ static auto PerformImplLookup(Context& context, SemIR::ConstantId type_const_id,
 // impl lookup if necessary. If the scope is invalid, assume an error has
 // already been diagnosed, and return BuiltinError.
 static auto LookupMemberNameInScope(Context& context,
-                                    Parse::MemberAccessExprId node_id,
+                                    Parse::AnyMemberAccessExprId node_id,
                                     SemIR::InstId /*base_id*/,
                                     SemIR::NameId name_id,
                                     SemIR::ConstantId name_scope_const_id,
@@ -231,7 +231,7 @@ static auto LookupMemberNameInScope(Context& context,
 // field, forms a class member access. If the found member is an instance
 // method, forms a bound method. Otherwise, the member is returned unchanged.
 static auto PerformInstanceBinding(Context& context,
-                                   Parse::MemberAccessExprId node_id,
+                                   Parse::AnyMemberAccessExprId node_id,
                                    SemIR::InstId base_id,
                                    SemIR::InstId member_id) -> SemIR::InstId {
   auto member_type_id = context.insts().Get(member_id).type_id();
@@ -295,7 +295,7 @@ static auto PerformInstanceBinding(Context& context,
   return member_id;
 }
 
-auto PerformMemberAccess(Context& context, Parse::MemberAccessExprId node_id,
+auto PerformMemberAccess(Context& context, Parse::AnyMemberAccessExprId node_id,
                          SemIR::InstId base_id, SemIR::NameId name_id)
     -> SemIR::InstId {
   // If the base is a name scope, such as a class or namespace, perform lookup
@@ -371,7 +371,7 @@ auto PerformMemberAccess(Context& context, Parse::MemberAccessExprId node_id,
 }
 
 auto PerformCompoundMemberAccess(Context& context,
-                                 Parse::MemberAccessExprId node_id,
+                                 Parse::AnyMemberAccessExprId node_id,
                                  SemIR::InstId base_id,
                                  SemIR::InstId member_expr_id)
     -> SemIR::InstId {

diff --git a/toolchain/check/member_access.h b/toolchain/check/member_access.h
@@ -12,15 +12,15 @@ namespace Carbon::Check {
 
 // Creates SemIR to perform a member access with base expression `base_id` and
 // member name `name_id`. Returns the result of the access.
-auto PerformMemberAccess(Context& context, Parse::MemberAccessExprId node_id,
+auto PerformMemberAccess(Context& context, Parse::AnyMemberAccessExprId node_id,
                          SemIR::InstId base_id, SemIR::NameId name_id)
     -> SemIR::InstId;
 
 // Creates SemIR to perform a compound member access with base expression
 // `base_id` and member name expression `member_expr_id`. Returns the result of
 // the access.
 auto PerformCompoundMemberAccess(Context& context,
-                                 Parse::MemberAccessExprId node_id,
+                                 Parse::AnyMemberAccessExprId node_id,
                                  SemIR::InstId base_id,
                                  SemIR::InstId member_expr_id) -> SemIR::InstId;
 

diff --git a/toolchain/check/pointer_dereference.cpp b/toolchain/check/pointer_dereference.cpp
@@ -0,0 +1,31 @@
+// 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 "llvm/ADT/STLFunctionalExtras.h"
+#include "toolchain/check/context.h"
+#include "toolchain/check/convert.h"
+#include "toolchain/parse/node_ids.h"
+#include "toolchain/sem_ir/ids.h"
+
+namespace Carbon::Check {
+
+auto PerformPointerDereference(
+    Context& context, Parse::AnyPointerDeferenceExprId node_id,
+    SemIR::InstId base_id,
+    llvm::function_ref<auto(SemIR::TypeId not_pointer_type_id)->void>
+        diagnose_not_pointer) -> SemIR::InstId {
+  base_id = ConvertToValueExpr(context, base_id);
+  auto type_id =
+      context.GetUnqualifiedType(context.insts().Get(base_id).type_id());
+  auto result_type_id = SemIR::TypeId::Error;
+  if (auto pointer_type =
+          context.types().TryGetAs<SemIR::PointerType>(type_id)) {
+    result_type_id = pointer_type->pointee_id;
+  } else if (type_id != SemIR::TypeId::Error) {
+    diagnose_not_pointer(type_id);
+  }
+  return context.AddInst({node_id, SemIR::Deref{result_type_id, base_id}});
+}
+
+}  // namespace Carbon::Check
diff --git a/toolchain/check/pointer_dereference.h b/toolchain/check/pointer_dereference.h
@@ -0,0 +1,25 @@
+// 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
+
+#ifndef CARBON_TOOLCHAIN_CHECK_POINTER_DEREFERENCE_H_
+#define CARBON_TOOLCHAIN_CHECK_POINTER_DEREFERENCE_H_
+
+#include "llvm/ADT/STLFunctionalExtras.h"
+#include "toolchain/check/context.h"
+#include "toolchain/parse/node_ids.h"
+#include "toolchain/sem_ir/ids.h"
+
+namespace Carbon::Check {
+
+// Creates SemIR to perform a pointer dereference with base expression
+// `base_id`. Returns the result of the access.
+auto PerformPointerDereference(
+    Context& context, Parse::AnyPointerDeferenceExprId node_id,
+    SemIR::InstId base_i,
+    llvm::function_ref<auto(SemIR::TypeId not_pointer_type_id)->void>
+        diagnose_not_pointer) -> SemIR::InstId;
+
+}  // namespace Carbon::Check
+
+#endif  // CARBON_TOOLCHAIN_CHECK_POINTER_DEREFERENCE_H_