Merge remote-tracking branch 'upstream/stable' into merge_stable

src/func.d

@@ -4451,38 +4451,13 @@ public:
          */
         if (ad && (!parent.isTemplateInstance() || parent.isTemplateMixin()))
         {
-            size_t dim = Parameter.dim(tf.parameters);
-            StructDeclaration sd = ad.isStructDeclaration();
-            if (sd)
-            {
-                bool allDefaultedParams = (dim == 0) && tf.varargs == 1;  // c-style: foo(...)
-                bool isDefCtor = dim == 0;
-
-                for (size_t i = 0; i < dim; i++)
-                {
-                    auto arg = Parameter.getNth(tf.parameters, i);
-
-                    // note: D-style variadic arguments allowed as a special-case (tf.varargs == 2)
-                    if (i + 1 == dim && arg.defaultArg)
-                    {
-                        isDefCtor = true;
-                        allDefaultedParams = true;
-                    }
-                    else
-                    {
-                        break;
-                    }
-                }
+            immutable dim = Parameter.dim(tf.parameters);
 
-                if (isDefCtor)
+            if (auto sd = ad.isStructDeclaration())
+            {
+                if (dim == 0 && tf.varargs == 0) // empty default ctor w/o any varargs
                 {
-                    if (allDefaultedParams)  // only warn for now
-                    {
-                        warning(loc, "%s %s default constructor for structs "
-                            "only allowed with @disable, no body, and no "
-                            "parameters", kind(), toPrettyChars());
-                    }
-                    else if (fbody || !(storage_class & STCdisable) || dim)
+                    if (fbody || !(storage_class & STCdisable))
                     {
                         error("default constructor for structs only allowed "
                             "with @disable, no body, and no parameters");
@@ -4491,6 +4466,22 @@ public:
                     }
                     sd.noDefaultCtor = true;
                 }
+                else if (dim == 0 && tf.varargs) // allow varargs only ctor
+                {
+                }
+                else if (dim && Parameter.getNth(tf.parameters, 0).defaultArg)
+                {
+                    // if the first parameter has a default argument, then the rest does as well
+                    if (storage_class & STCdisable)
+                    {
+                        deprecation("@disable'd constructor cannot have default "~
+                                    "arguments for all parameters.");
+                        deprecationSupplemental(loc, "Use @disable this(); if you want to disable default initialization.");
+                    }
+                    else
+                        deprecation("all parameters have default arguments, "~
+                                    "but structs cannot have default constructors.");
+                }
             }
             else if (dim == 0 && tf.varargs == 0)
             {

test/compilable/compile1.d

@@ -937,3 +937,5 @@ import core.vararg;
 struct S3438_1 { this(int x, int y = 1) { } }
 struct S3438_2 { this(int x, ...) { } }
 struct S3438_3 { this(int x, int[] arr...) { } }
+struct S3438_4 { this(...) { } }
+struct S3438_5 { this(int[] arr...) { } }

test/fail_compilation/diag3438.d

@@ -1,20 +1,21 @@
-// REQUIRED_ARGS: -w
+// REQUIRED_ARGS: -de
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/diag3438.d(15): Warning: constructor diag3438.F1.this default constructor for structs only allowed with @disable, no body, and no parameters
-fail_compilation/diag3438.d(16): Warning: constructor diag3438.F2.this default constructor for structs only allowed with @disable, no body, and no parameters
-fail_compilation/diag3438.d(17): Warning: constructor diag3438.F3.this default constructor for structs only allowed with @disable, no body, and no parameters
-fail_compilation/diag3438.d(19): Warning: constructor diag3438.F5.this default constructor for structs only allowed with @disable, no body, and no parameters
-fail_compilation/diag3438.d(20): Warning: constructor diag3438.F6.this default constructor for structs only allowed with @disable, no body, and no parameters
+fail_compilation/diag3438.d(16): Deprecation: constructor diag3438.F1.this all parameters have default arguments, but structs cannot have default constructors.
+fail_compilation/diag3438.d(17): Deprecation: constructor diag3438.F2.this all parameters have default arguments, but structs cannot have default constructors.
+fail_compilation/diag3438.d(20): Deprecation: constructor diag3438.F5.this @disable'd constructor cannot have default arguments for all parameters.
+fail_compilation/diag3438.d(20): Deprecation: Use @disable this(); if you want to disable default initialization.
+fail_compilation/diag3438.d(21): Deprecation: constructor diag3438.F6.this @disable'd constructor cannot have default arguments for all parameters.
+fail_compilation/diag3438.d(21): Deprecation: Use @disable this(); if you want to disable default initialization.
 ---
 */
 
 import core.vararg;
 
 struct F1 { this(int x = 1) { } }
 struct F2 { this(int x = 1, ...) { } }
-struct F3 { this(...) { } }
+struct F3 { this(...) { } } // ok
 struct F4 { this(int[] x...) { } }  // ok
 struct F5 { @disable this(int x = 1); }
 struct F6 { @disable this(int x = 1) { } }

test/fail_compilation/diag3438b.d

@@ -0,0 +1,9 @@
+/*
+TEST_OUTPUT:
+---
+fail_compilation/diag3438b.d(9): Error: default argument expected for y
+---
+*/
+
+// Make sure the deprecation doesn't interfere w/ the check for default arguments
+struct S { this(int x = 1, int y) { } }