From 0dd91169910202e41c524962b4bc00dc16c67c2b Mon Sep 17 00:00:00 2001
From: k-hara <k.hara.pg@gmail.com>
Date: Fri, 17 Jul 2015 14:24:26 +0900
Subject: [PATCH] fix Issue 14802 - Template argument deduction depends on
 order of arguments

---
 src/dcast.d               | 23 ++++++++++++++++++++++
 src/dtemplate.d           | 26 ++++++++++++++++++++++---
 test/runnable/template9.d | 41 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+), 3 deletions(-)

diff --git a/src/dcast.d b/src/dcast.d
index 356ce4a8d771..08e3d85d77b0 100644
--- a/src/dcast.d
+++ b/src/dcast.d
@@ -2431,6 +2431,29 @@ extern (C++) bool isVoidArrayLiteral(Expression e, Type other)
     return (e.op == TOKarrayliteral && t.ty == Tarray && t.nextOf().ty == Tvoid && (cast(ArrayLiteralExp)e).elements.dim == 0);
 }
 
+// used by deduceType()
+extern (C++) Type rawTypeMerge(Type t1, Type t2)
+{
+    Type t1b = t1.toBasetype();
+    Type t2b = t2.toBasetype();
+
+    if (t1.equals(t2))
+    {
+        return t1;
+    }
+    else if (t1b.equals(t2b))
+    {
+        return t1b;
+    }
+    else
+    {
+        TY ty = cast(TY)impcnvResult[t1b.ty][t2b.ty];
+        if (ty != Terror)
+            return Type.basic[ty];
+    }
+    return null;
+}
+
 /**************************************
  * Combine types.
  * Output:
diff --git a/src/dtemplate.d b/src/dtemplate.d
index 06f2c226323b..c525b9c01512 100644
--- a/src/dtemplate.d
+++ b/src/dtemplate.d
@@ -4052,9 +4052,7 @@ extern (C++) MATCH deduceType(RootObject o, Scope* sc, Type tparam, TemplatePara
                 at = xt.tded;
             }
             // From previous matched expressions to current deduced type
-            MATCH match1 = MATCHnomatch;
-            if (xt)
-                match1 = xt.matchAll(tt);
+            MATCH match1 = xt ? xt.matchAll(tt) : MATCHnomatch;
             // From current expresssion to previous deduced type
             Type pt = at.addMod(tparam.mod);
             if (*wm)
@@ -4086,6 +4084,11 @@ extern (C++) MATCH deduceType(RootObject o, Scope* sc, Type tparam, TemplatePara
                     }
                     //printf("tt = %s, at = %s\n", tt->toChars(), at->toChars());
                 }
+                else
+                {
+                    match1 = MATCHnomatch;
+                    match2 = MATCHnomatch;
+                }
             }
             if (match1 > MATCHnomatch)
             {
@@ -4105,6 +4108,23 @@ extern (C++) MATCH deduceType(RootObject o, Scope* sc, Type tparam, TemplatePara
                 result = match2;
                 return;
             }
+
+            /* Deduce common type
+             */
+            if (Type t = rawTypeMerge(at, tt))
+            {
+                if (xt)
+                    xt.update(t, e, tparam);
+                else
+                    (*dedtypes)[i] = t;
+
+                pt = tt.addMod(tparam.mod);
+                if (*wm)
+                    pt = pt.substWildTo(*wm);
+                result = e.implicitConvTo(pt);
+                return;
+            }
+
             result = MATCHnomatch;
         }
 
diff --git a/test/runnable/template9.d b/test/runnable/template9.d
index 63024c296e27..032e7d93adc1 100644
--- a/test/runnable/template9.d
+++ b/test/runnable/template9.d
@@ -4629,6 +4629,46 @@ class A14743
     auto func2(T)() {}
 }
 
+/******************************************/
+// 14802
+
+void test14802()
+{
+    auto func(T)(T x, T y) { return x; }
+
+    struct S1 { double x; alias x this; }
+    struct S2 { double x; alias x this; }
+    S1 s1;
+    S2 s2;
+
+    enum E1 : double { a = 1.0 }
+    enum E2 : double { a = 1.0 }
+
+    static assert(is(typeof( func(1 , 1 ) ) == int));
+    static assert(is(typeof( func(1u, 1u) ) == uint));
+    static assert(is(typeof( func(1u, 1 ) ) == uint));
+    static assert(is(typeof( func(1 , 1u) ) == uint));
+
+    static assert(is(typeof( func(1.0f, 1.0f) ) == float));
+    static assert(is(typeof( func(1.0 , 1.0 ) ) == double));
+    static assert(is(typeof( func(1.0 , 1.0f) ) == double));
+    static assert(is(typeof( func(1.0f, 1.0 ) ) == double));
+
+    static assert(is(typeof( func(s1, s1) ) == S1));
+    static assert(is(typeof( func(s2, s2) ) == S2));
+    static assert(is(typeof( func(s1, s2) ) == double));
+    static assert(is(typeof( func(s2, s1) ) == double));
+
+    static assert(is(typeof( func(E1.a, E1.a) ) == E1));
+    static assert(is(typeof( func(E2.a, E2.a) ) == E2));
+    static assert(is(typeof( func(E1.a, 1.0)  ) == double));
+    static assert(is(typeof( func(E2.a, 1.0)  ) == double));
+    static assert(is(typeof( func(1.0,  E1.a) ) == double));
+    static assert(is(typeof( func(1.0,  E2.a) ) == double));
+    static assert(is(typeof( func(E1.a, E2.a) ) == double));
+    static assert(is(typeof( func(E2.a, E1.a) ) == double));
+}
+
 /******************************************/
 
 int main()
@@ -4741,6 +4781,7 @@ int main()
     test13694();
     test14836();
     test14735();
+    test14802();
 
     printf("Success\n");
     return 0;