Rename files to use abbreviations (#3389)

Reflects these recent PRs:
* #3375 
* #3382

toolchain/parse/handle_call_expr.cpp

@@ -0,0 +1,45 @@
+// 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 HandleCallExpr(Context& context) -> void {
+  auto state = context.PopState();
+
+  state.state = State::CallExprFinish;
+  context.PushState(state);
+
+  context.AddNode(NodeKind::CallExprStart, context.Consume(),
+                  state.subtree_start, state.has_error);
+  if (!context.PositionIs(Lex::TokenKind::CloseParen)) {
+    context.PushState(State::CallExprParameterFinish);
+    context.PushState(State::Expr);
+  }
+}
+
+auto HandleCallExprParameterFinish(Context& context) -> void {
+  auto state = context.PopState();
+
+  if (state.has_error) {
+    context.ReturnErrorOnState();
+  }
+
+  if (context.ConsumeListToken(NodeKind::CallExprComma,
+                               Lex::TokenKind::CloseParen, state.has_error) ==
+      Context::ListTokenKind::Comma) {
+    context.PushState(State::CallExprParameterFinish);
+    context.PushState(State::Expr);
+  }
+}
+
+auto HandleCallExprFinish(Context& context) -> void {
+  auto state = context.PopState();
+
+  context.AddNode(NodeKind::CallExpr, context.Consume(), state.subtree_start,
+                  state.has_error);
+}
+
+}  // namespace Carbon::Parse