Respond to reviewer comments

toolchain/check/handle_variable.cpp

@@ -37,6 +37,7 @@ auto HandleVariableDecl(Context& context, Parse::NodeId parse_node) -> bool {
  if (next_kind == Parse::NodeKind::ParamList) {
  return context.TODO(parse_node, "tuple pattern in var");
  }
+ // TODO: find a more robust way to determine if there was an initializer.
  bool has_init = next_kind != Parse::NodeKind::BindingPattern;
  if (has_init) {
  init_id = context.node_stack().PopExpr();

toolchain/parse/context.cpp

@@ -150,16 +150,6 @@ auto Context::ConsumeIf(Lex::TokenKind kind) -> std::optional<Lex::TokenIndex> {
  return Consume();
 }
 
-auto Context::ConsumeIfBindingPatternKeyword(Lex::TokenKind keyword_token,
- State keyword_state,
- int subtree_start) -> void {
- if (auto token = ConsumeIf(keyword_token)) {
- PushState(Context::StateStackEntry(
- keyword_state, PrecedenceGroup::ForTopLevelExpr(),
- PrecedenceGroup::ForTopLevelExpr(), *token, subtree_start));
- }
-}
-
 auto Context::FindNextOf(std::initializer_list<Lex::TokenKind> desired_kinds)
  -> std::optional<Lex::TokenIndex> {
  auto new_position = position_;

toolchain/parse/context.h

@@ -285,11 +285,6 @@ class Context {
  // Propagates an error up the state stack, to the parent state.
  auto ReturnErrorOnState() -> void { state_stack_.back().has_error = true; }
 
- // For HandleBindingPattern, tries to consume a wrapping keyword.
- auto ConsumeIfBindingPatternKeyword(Lex::TokenKind keyword_token,
- State keyword_state, int subtree_start)
- -> void;
-
  // Emits a diagnostic for a declaration missing a semi.
  auto EmitExpectedDeclSemi(Lex::TokenKind expected_kind) -> void;
 

toolchain/parse/handle_binding_pattern.cpp

@@ -11,11 +11,17 @@ auto HandleBindingPattern(Context& context) -> void {
 
  // Parameters may have keywords prefixing the pattern. They become the parent
  // for the full BindingPattern.
- context.ConsumeIfBindingPatternKeyword(Lex::TokenKind::Template,
- State::BindingPatternTemplate,
- state.subtree_start);
- context.ConsumeIfBindingPatternKeyword(
- Lex::TokenKind::Addr, State::BindingPatternAddress, state.subtree_start);
+ if (auto token = context.ConsumeIf(Lex::TokenKind::Template)) {
+ context.PushState(Context::StateStackEntry(
+ State::BindingPatternTemplate, PrecedenceGroup::ForTopLevelExpr(),
+ PrecedenceGroup::ForTopLevelExpr(), *token, state.subtree_start));
+ }
+
+ if (auto token = context.ConsumeIf(Lex::TokenKind::Addr)) {
+ context.PushState(Context::StateStackEntry(
+ State::BindingPatternAddress, PrecedenceGroup::ForTopLevelExpr(),
+ PrecedenceGroup::ForTopLevelExpr(), *token, state.subtree_start));
+ }
 
  // Handle an invalid pattern introducer for parameters and variables.
  auto on_error = [&]() {

toolchain/parse/handle_let.cpp

@@ -16,11 +16,7 @@ auto HandleLet(Context& context) -> void {
  context.AddLeafNode(NodeKind::LetIntroducer, context.Consume());
 
  // This will start at the pattern.
- if (context.PositionKind() == Lex::TokenKind::OpenParen) {
- context.PushState(State::ParamListAsRegular);
- } else {
- context.PushState(State::BindingPattern);
- }
+ context.PushState(State::Pattern);
 }
 
 auto HandleLetAfterPattern(Context& context) -> void {

toolchain/parse/handle_pattern.cpp

@@ -0,0 +1,18 @@
+// 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/parse/context.h"
+
+namespace Carbon::Parse {
+
+auto HandlePattern(Context& context) -> void {
+ context.PopAndDiscardState();
+ if (context.PositionKind() == Lex::TokenKind::OpenParen) {
+ context.PushState(State::ParamListAsRegular);
+ } else {
+ context.PushState(State::BindingPattern);
+ }
+}
+
+} // namespace Carbon::Parse

toolchain/parse/handle_var.cpp

@@ -23,11 +23,7 @@ static auto HandleVar(Context& context, State finish_state,
  context.AddLeafNode(NodeKind::ReturnedModifier, returned_token);
  }
 
- if (context.PositionKind() == Lex::TokenKind::OpenParen) {
- context.PushState(State::ParamListAsRegular);
- } else {
- context.PushState(State::BindingPattern);
- }
+ context.PushState(State::Pattern);
 }
 
 auto HandleVarAsDecl(Context& context) -> void {

toolchain/parse/state.def

@@ -739,6 +739,17 @@ CARBON_PARSE_STATE_VARIANTS2(ParenExprParamFinish, Unknown, Tuple)
 // (state done)
 CARBON_PARSE_STATE_VARIANTS2(ParenExprFinish, Normal, Tuple)
 
+// Handles processing of a pattern.
+//
+// ( ... )
+// ^
+// 1. ParamListAsRegular
+//
+// ...
+// ^
+// 1. BindingPattern
+CARBON_PARSE_STATE(Pattern)
+
 // Handles the initial part of a binding pattern, enqueuing type expression
 // processing.
 //