[flang] Ensure overrides of special procedures (llvm#142465)

When a derived type declares a generic procedure binding of interest to
the runtime library, such as for ASSIGNMENT(=), it overrides any binding
that might have been present for the parent type.

Fixes llvm#142414.

Author: klausler

flang/lib/Semantics/runtime-type-info.cpp

@@ -1067,7 +1067,7 @@ RuntimeTableBuilder::DescribeSpecialGenerics(const Scope &dtScope,
     specials =
         DescribeSpecialGenerics(*parentScope, thisScope, derivedTypeSpec);
   }
-  for (auto pair : dtScope) {
+  for (const auto &pair : dtScope) {
     const Symbol &symbol{*pair.second};
     if (const auto *generic{symbol.detailsIf<GenericDetails>()}) {
       DescribeSpecialGeneric(*generic, specials, thisScope, derivedTypeSpec);
@@ -1245,7 +1245,7 @@ void RuntimeTableBuilder::DescribeSpecialProc(
     AddValue(values, specialSchema_, procCompName,
         SomeExpr{evaluate::ProcedureDesignator{specific}});
     // index might already be present in the case of an override
-    specials.emplace(*index,
+    specials.insert_or_assign(*index,
         evaluate::StructureConstructor{
             DEREF(specialSchema_.AsDerived()), std::move(values)});
   }

flang/test/Semantics/typeinfo13.f90

@@ -0,0 +1,26 @@
+!RUN: %flang_fc1 -fdebug-dump-symbols %s | FileCheck %s
+!Ensure ASSIGNMENT(=) overrides are applied to the special procedures table.
+module m
+  type base
+   contains
+    procedure :: baseAssign
+    generic :: assignment(=) => baseAssign
+  end type
+  type, extends(base) :: child
+   contains
+    procedure :: override
+    generic :: assignment(=) => override
+  end type
+ contains
+  impure elemental subroutine baseAssign(to, from)
+    class(base), intent(out) :: to
+    type(base), intent(in) :: from
+  end
+  impure elemental subroutine override(to, from)
+    class(child), intent(out) :: to
+    type(child), intent(in) :: from
+  end
+end
+
+!CHECK: .s.child, SAVE, TARGET (CompilerCreated, ReadOnly): ObjectEntity type: TYPE(specialbinding) shape: 0_8:0_8 init:[specialbinding::specialbinding(which=2_1,isargdescriptorset=1_1,istypebound=1_1,isargcontiguousset=0_1,proc=override)]
+!CHECK: .v.child, SAVE, TARGET (CompilerCreated, ReadOnly): ObjectEntity type: TYPE(binding) shape: 0_8:1_8 init:[binding::binding(proc=baseassign,name=.n.baseassign),binding(proc=override,name=.n.override)]