Clean up obsolete import handling in class/function (#4857)

Noticed because the `new_loc.inst_id` use would be invalid as-is

toolchain/check/handle_class.cpp

@@ -14,6 +14,7 @@
 #include "toolchain/check/merge.h"
 #include "toolchain/check/modifiers.h"
 #include "toolchain/check/name_component.h"
+#include "toolchain/parse/node_ids.h"
 #include "toolchain/sem_ir/function.h"
 #include "toolchain/sem_ir/ids.h"
 #include "toolchain/sem_ir/inst.h"
@@ -53,9 +54,8 @@ auto HandleParseNode(Context& context, Parse::ClassIntroducerId node_id)
 //
 // If merging is successful, returns true and may update the previous class.
 // Otherwise, returns false. Prints a diagnostic when appropriate.
-static auto MergeClassRedecl(Context& context, SemIRLoc new_loc,
-                             SemIR::Class& new_class, bool new_is_import,
-                             bool new_is_definition,
+static auto MergeClassRedecl(Context& context, Parse::AnyClassDeclId node_id,
+                             SemIR::Class& new_class, bool new_is_definition,
                              SemIR::ClassId prev_class_id,
                              SemIR::ImportIRId prev_import_ir_id) -> bool {
   auto& prev_class = context.classes().Get(prev_class_id);
@@ -69,7 +69,7 @@ static auto MergeClassRedecl(Context& context, SemIRLoc new_loc,
 
   DiagnoseIfInvalidRedecl(
       context, Lex::TokenKind::Class, prev_class.name_id,
-      RedeclInfo(new_class, new_loc, new_is_definition),
+      RedeclInfo(new_class, node_id, new_is_definition),
       RedeclInfo(prev_class, prev_loc, prev_class.has_definition_started()),
       prev_import_ir_id);
 
@@ -87,12 +87,11 @@ static auto MergeClassRedecl(Context& context, SemIRLoc new_loc,
     prev_class.complete_type_witness_id = new_class.complete_type_witness_id;
   }
 
-  if ((prev_import_ir_id.has_value() && !new_is_import) ||
+  if (prev_import_ir_id.has_value() ||
       (prev_class.is_extern && !new_class.is_extern)) {
     prev_class.first_owning_decl_id = new_class.first_owning_decl_id;
-    ReplacePrevInstForMerge(
-        context, new_class.parent_scope_id, prev_class.name_id,
-        new_is_import ? new_loc.inst_id : new_class.first_owning_decl_id);
+    ReplacePrevInstForMerge(context, new_class.parent_scope_id,
+                            prev_class.name_id, new_class.first_owning_decl_id);
   }
   return true;
 }
@@ -165,9 +164,8 @@ static auto MergeOrAddName(Context& context, Parse::AnyClassDeclId node_id,
 
   // TODO: Fix `extern` logic. It doesn't work correctly, but doesn't seem worth
   // ripping out because existing code may incrementally help.
-  if (MergeClassRedecl(context, node_id, class_info,
-                       /*new_is_import=*/false, is_definition, prev_class_id,
-                       prev_import_ir_id)) {
+  if (MergeClassRedecl(context, node_id, class_info, is_definition,
+                       prev_class_id, prev_import_ir_id)) {
     // When merging, use the existing entity rather than adding a new one.
     class_decl.class_id = prev_class_id;
     class_decl.type_id = prev.type_id();

toolchain/check/handle_function.cpp

@@ -77,9 +77,10 @@ static auto DiagnoseModifiers(Context& context, DeclIntroducerState& introducer,
 //
 // If merging is successful, returns true and may update the previous function.
 // Otherwise, returns false. Prints a diagnostic when appropriate.
-static auto MergeFunctionRedecl(Context& context, SemIRLoc new_loc,
+static auto MergeFunctionRedecl(Context& context,
+                                Parse::AnyFunctionDeclId node_id,
                                 SemIR::Function& new_function,
-                                bool new_is_import, bool new_is_definition,
+                                bool new_is_definition,
                                 SemIR::FunctionId prev_function_id,
                                 SemIR::ImportIRId prev_import_ir_id) -> bool {
   auto& prev_function = context.functions().Get(prev_function_id);
@@ -90,7 +91,7 @@ static auto MergeFunctionRedecl(Context& context, SemIRLoc new_loc,
 
   DiagnoseIfInvalidRedecl(
       context, Lex::TokenKind::Fn, prev_function.name_id,
-      RedeclInfo(new_function, new_loc, new_is_definition),
+      RedeclInfo(new_function, node_id, new_is_definition),
       RedeclInfo(prev_function, prev_function.latest_decl_id(),
                  prev_function.has_definition_started()),
       prev_import_ir_id);
@@ -107,7 +108,7 @@ static auto MergeFunctionRedecl(Context& context, SemIRLoc new_loc,
     prev_function.MergeDefinition(new_function);
     prev_function.return_slot_pattern_id = new_function.return_slot_pattern_id;
   }
-  if ((prev_import_ir_id.has_value() && !new_is_import)) {
+  if (prev_import_ir_id.has_value()) {
     ReplacePrevInstForMerge(context, new_function.parent_scope_id,
                             prev_function.name_id,
                             new_function.first_owning_decl_id);
@@ -162,8 +163,7 @@ static auto TryMergeRedecl(Context& context, Parse::AnyFunctionDeclId node_id,
     return;
   }
 
-  if (MergeFunctionRedecl(context, node_id, function_info,
-                          /*new_is_import=*/false, is_definition,
+  if (MergeFunctionRedecl(context, node_id, function_info, is_definition,
                           prev_function_id, prev_import_ir_id)) {
     // When merging, use the existing function rather than adding a new one.
     function_decl.function_id = prev_function_id;