From 90fa4fb85a1b3e28c10eb5b93be64c20fd8a7086 Mon Sep 17 00:00:00 2001
From: John Hodge <tpg@mutabah.net>
Date: Wed, 9 Nov 2016 21:57:32 +0800
Subject: HIR Typecheck Expr - Restrict ivar guesses to pick the most
 compatible

---
 src/hir_typeck/expr_cs.cpp | 47 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/src/hir_typeck/expr_cs.cpp b/src/hir_typeck/expr_cs.cpp
index 1f6dccdc..45de4850 100644
--- a/src/hir_typeck/expr_cs.cpp
+++ b/src/hir_typeck/expr_cs.cpp
@@ -4935,6 +4935,31 @@ namespace {
                         return context.m_ivars.types_equal(*s_e.inner, *d_e.inner);
                     }
                 }
+                
+                if( dst.m_data.is_Pointer() && src.m_data.is_Pointer() ) {
+                    const auto& d_e = dst.m_data.as_Pointer();
+                    const auto& s_e = src.m_data.as_Pointer();
+                    // Higher = more specific (e.g. Unique > Shared)
+                    if( s_e.type < d_e.type ) {
+                        return false;
+                    }
+                    else if( s_e.type == d_e.type ) {
+                        // Check relationship
+                        // - 1. Deref chain.
+                        // - 2. Trait object?
+                    }
+                    else {
+                        return context.m_ivars.types_equal(*s_e.inner, *d_e.inner);
+                    }
+                }
+                
+                if( dst.m_data.is_Pointer() && src.m_data.is_Borrow() ) {
+                    const auto& d_e = dst.m_data.as_Pointer();
+                    const auto& s_e = src.m_data.as_Borrow();
+                    if( s_e.type == d_e.type ) {
+                        return context.m_ivars.types_equal(*s_e.inner, *d_e.inner);
+                    }
+                }
                 return false;
             }
             
@@ -5011,6 +5036,28 @@ namespace {
             #endif
             
             // Prefer cases where this type is being created from a known type
+            if( ivar_ent.types_from.size() == 0 && ivar_ent.types_to.size() == 0 ) {
+                ivar_ent.reset();
+                return ;
+            }
+            DEBUG("-- " << ty_l << " FROM=" << ivar_ent.types_from << ", TO=" << ivar_ent.types_to);
+            
+            #if 1
+            if( ivar_ent.types_from.size() == 1 && ivar_ent.types_to.size() == 1 ) {
+                const auto& ty_to = ivar_ent.types_to[0];
+                const auto& ty_from = ivar_ent.types_from[0];
+                if( H::can_coerce_to(context, ty_to, ty_from) )
+                {
+                    // Only one possibility
+                    DEBUG("- IVar " << ty_l << " = " << ty_to << " (to)");
+                    context.equate_types(sp, ty_l, ty_to);
+                    
+                    ivar_ent.reset();
+                    return ;
+                }
+            }
+            //else
+            #endif
             if( ivar_ent.types_from.size() == 1 ) {
                 //const ::HIR::TypeRef& ty_r = *ivar_ent.types_from[0];
                 const ::HIR::TypeRef& ty_r = ivar_ent.types_from[0];
-- 
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