fix Issue 20610 aliasing for fields does not work

compiler/src/dmd/declaration.d

@@ -612,8 +612,9 @@ extern (C++) final class AliasDeclaration : Declaration
 
     override Dsymbol toAlias()
     {
-        //printf("[%s] AliasDeclaration::toAlias('%s', this = %p, aliassym = %p, kind = '%s', inuse = %d)\n",
-        //    loc.toChars(), toChars(), this, aliassym, aliassym ? aliassym.kind() : "", inuse);
+        static if (0)
+        printf("[%s] AliasDeclaration::toAlias('%s', this = %p, aliassym: %s, kind: '%s', inuse = %d)\n",
+            loc.toChars(), toChars(), this, aliassym ? aliassym.toChars() : "", aliassym ? aliassym.kind() : "", inuse);
         assert(this != aliassym);
         //static int count; if (++count == 10) *(char*)0=0;
 

compiler/src/dmd/dsymbolsem.d

@@ -5243,7 +5243,7 @@ void aliasInstanceSemantic(TemplateInstance tempinst, Scope* sc, TemplateDeclara
 // function used to perform semantic on AliasDeclaration
 void aliasSemantic(AliasDeclaration ds, Scope* sc)
 {
-    //printf("AliasDeclaration::semantic() %s\n", ds.toChars());
+    //printf("AliasDeclaration::semantic() %s %p\n", ds.toChars(), ds.aliassym);
 
     // as DsymbolSemanticVisitor::visit(AliasDeclaration), in case we're called first.
     // see https://issues.dlang.org/show_bug.cgi?id=21001

compiler/src/dmd/expressionsem.d

@@ -8138,7 +8138,7 @@ private extern (C++) final class ExpressionSemanticVisitor : Visitor
         static if (LOGSEMANTIC)
         {
             printf("DotIdExp::semantic(this = %p, '%s')\n", exp, exp.toChars());
-            //printf("e1.op = %d, '%s'\n", e1.op, Token.toChars(e1.op));
+            printAST(exp);
         }
 
         if (sc.inCfile)
@@ -14037,7 +14037,7 @@ Expression expressionSemantic(Expression e, Scope* sc)
 
 private Expression dotIdSemanticPropX(DotIdExp exp, Scope* sc)
 {
-    //printf("DotIdExp::semanticX(this = %p, '%s')\n", this, toChars());
+    //printf("dotIdSemanticPropX() %s\n", toChars(exp));
     if (Expression ex = unaSemantic(exp, sc))
         return ex;
 
@@ -14165,7 +14165,7 @@ private Expression dotIdSemanticPropX(DotIdExp exp, Scope* sc)
  */
 Expression dotIdSemanticProp(DotIdExp exp, Scope* sc, bool gag)
 {
-    //printf("DotIdExp::semanticY(this = %p, '%s')\n", exp, exp.toChars());
+    //printf("dotIdSemanticProp('%s')\n", exp.toChars());
 
     //{ static int z; fflush(stdout); if (++z == 10) *(char*)0=0; }
 
@@ -14503,7 +14503,7 @@ Expression dotIdSemanticProp(DotIdExp exp, Scope* sc, bool gag)
 
         const flag = cast(DotExpFlag) (exp.noderef * DotExpFlag.noDeref | gag * DotExpFlag.gag);
 
-        Expression e = exp.e1.type.dotExp(sc, exp.e1, exp.ident, flag);
+        Expression e = dotExp(exp.e1.type, sc, exp.e1, exp.ident, flag);
         if (e)
         {
             e = e.expressionSemantic(sc);

compiler/src/dmd/printast.d

@@ -51,6 +51,12 @@ extern (C++) final class PrintASTVisitor : Visitor
         printf("%.*s %s\n", cast(int)s.length, s.ptr, e.type ? e.type.toChars() : "");
     }
 
+    override void visit(IdentifierExp e)
+    {
+        printIndent(indent);
+        printf("Identifier `%s` %s\n", e.ident.toChars(), e.type ? e.type.toChars() : "");
+    }
+
     override void visit(IntegerExp e)
     {
         printIndent(indent);

compiler/src/dmd/typesem.d

@@ -4462,6 +4462,10 @@ void resolve(Type mt, const ref Loc loc, Scope* sc, out Expression pe, out Type
  */
 Expression dotExp(Type mt, Scope* sc, Expression e, Identifier ident, DotExpFlag flag)
 {
+    enum LOGDOTEXP = false;
+    if (LOGDOTEXP)
+        printf("dotExp()\n");
+
     Expression visitType(Type mt)
     {
         VarDeclaration v = null;
@@ -5082,8 +5086,28 @@ Expression dotExp(Type mt, Scope* sc, Expression e, Identifier ident, DotExpFlag
             return noMember(mt, sc, e, ident, flag);
         }
         // check before alias resolution; the alias itself might be deprecated!
-        if (s.isAliasDeclaration)
+        if (auto ad = s.isAliasDeclaration)
+        {
             s.checkDeprecated(e.loc, sc);
+
+            // Fix for https://github.com/dlang/dmd/issues/20610
+            if (ad.originalType)
+            {
+                if (auto tid = ad.originalType.isTypeIdentifier())
+                {
+                    //printf("tid type: %s\n", toChars(tid));
+                    if (tid.idents.length)
+                    {
+                        /* Rewrite e.s as e.(tid.ident).(tid.idents)
+                         */
+                        e = new DotIdExp(e.loc, e, tid.ident);
+                        foreach (id; tid.idents) // maybe use typeToExpressionHelper()
+                            e = new DotIdExp(e.loc, e, cast(Identifier)id);
+                        return e.expressionSemantic(sc);
+                    }
+                }
+            }
+        }
         s = s.toAlias();
 
         if (auto em = s.isEnumMember())
@@ -6074,7 +6098,7 @@ Dsymbol toDsymbol(Type type, Scope* sc)
 
     Dsymbol visitIdentifier(TypeIdentifier type)
     {
-        //printf("TypeIdentifier::toDsymbol('%s')\n", toChars());
+        //printf("TypeIdentifier::toDsymbol('%s')\n", toChars(type));
         if (!sc)
             return null;
 
@@ -6086,7 +6110,6 @@ Dsymbol toDsymbol(Type type, Scope* sc)
             s = t.toDsymbol(sc);
         if (e)
             s = getDsymbol(e);
-
         return s;
     }
 

compiler/test/runnable/aliasassign.d

@@ -15,7 +15,7 @@ template Qual(alias T)
     alias Qual = T;
 }
 
-void test()
+void test1()
 {
     int x = 3;
     int y = 4;
@@ -25,7 +25,33 @@ void test()
     assert(XY[1] == 4);
 }
 
-void main()
+/**********************************************/
+
+struct T
+{
+    int k,i = 2;
+}
+
+struct S
+{
+    int x;
+    T t;
+    alias ti = t.i;
+}
+
+void test2()
+{
+    T t = T(1, 2);
+    S s;
+    assert(s.ti == 2);
+}
+
+/**********************************************/
+
+int main()
 {
-    test();
+    test1();
+    test2();
+
+    return 0;
 }