Fix Issue 19635 - -checkaction=context not working with attributes

src/core/internal/dassert.d

@@ -37,7 +37,7 @@ private template getPrintfFormat(T)
 Minimalistic formatting for use in _d_assert_fail to keep the compilation
 overhead small and avoid the use of Phobos.
 */
-auto miniFormat(V)(auto ref V v)
+auto miniFormat(V)(V v)
 {
     import core.stdc.stdio : sprintf;
     import core.stdc.string : strlen;
@@ -49,14 +49,14 @@ auto miniFormat(V)(auto ref V v)
     {
         enum printfFormat = getPrintfFormat!V;
         char[20] val;
-        sprintf(val.ptr, printfFormat, v);
-        return val.idup[0 .. strlen(val.ptr)];
+        auto len = sprintf(&val[0], printfFormat, v);
+        return val.idup[0 .. len];
     }
     else static if (__traits(isFloating, V))
     {
         char[60] val;
-        sprintf(val.ptr, "%g", v);
-        return val.idup[0 .. strlen(val.ptr)];
+        auto len = sprintf(&val[0], "%g", v);
+        return val.idup[0 .. len];
     }
     else static if (__traits(compiles, { string s = V.init.toString(); }))
     {
@@ -153,3 +153,26 @@ string invertCompToken(string comp)
     }
 }
 
+private auto assumeFakeAttributes(T)(T t) @trusted
+{
+    import core.internal.traits : Parameters, ReturnType;
+    alias RT = ReturnType!T;
+    alias P = Parameters!T;
+    alias type = RT function(P) nothrow @nogc @safe pure;
+    return cast(type) t;
+}
+
+auto miniFormatFakeAttributes(T)(T t)
+{
+    alias miniT = miniFormat!T;
+    return assumeFakeAttributes(&miniT)(t);
+}
+
+auto pureAlloc(size_t t)
+{
+    static auto alloc(size_t len)
+    {
+        return new ubyte[len];
+    }
+    return assumeFakeAttributes(&alloc)(t);
+}

src/object.d

@@ -4819,11 +4819,29 @@ TTo[] __ArrayCast(TFrom, TTo)(TFrom[] from) @nogc pure @trusted
 }
 
 // Allows customized assert error messages
-string _d_assert_fail(string comp, A, B)(A a, B b)
+string _d_assert_fail(string comp, A, B)(A a, B b) @nogc @safe nothrow pure
 {
-    import core.internal.dassert : invertCompToken, miniFormat;
-    auto valA = miniFormat(a);
-    auto valB = miniFormat(b);
+    import core.internal.dassert : invertCompToken, miniFormatFakeAttributes, pureAlloc;
+    /*
+    The program will be terminated after the assertion error message has
+    been printed and its not considered part of the "main" program.
+    Also, catching an AssertError is Undefined Behavior
+    Hence, we can fake purity and @nogc-ness here.
+    */
+
+    auto valA = miniFormatFakeAttributes(a);
+    auto valB = miniFormatFakeAttributes(b);
     enum token = invertCompToken(comp);
-    return valA ~ " " ~ token ~ " " ~ valB;
+
+    const totalLen = valA.length + token.length + valB.length + 2;
+    char[] buffer = cast(char[]) pureAlloc(totalLen)[0 .. totalLen];
+    // @nogc-concat of "<valA> <comp> <valB>"
+    auto n = valA.length;
+    buffer[0 .. n] = valA;
+    buffer[n++] = ' ';
+    buffer[n .. n + token.length] = token;
+    n += token.length;
+    buffer[n++] = ' ';
+    buffer[n .. n + valB.length] = valB;
+    return buffer;
 }

test/exceptions/src/assert_fail.d

@@ -112,6 +112,13 @@ void testAA()()
     test!"in"("foo", ["bar": true], `"foo" !in ["bar": true]`);
 }
 
+
+void testAttributes() @safe pure @nogc nothrow
+{
+    int a;
+    assert(a == 0);
+}
+
 void main()
 {
     testIntegers();
@@ -122,5 +129,6 @@ void main()
     testArray();
     testStruct();
     testAA();
+    testAttributes();
     fprintf(stderr, "success.\n");
 }