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replace delegate with simple nested function #8530

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Merged
merged 2 commits into from
Aug 12, 2022
Merged

replace delegate with simple nested function #8530

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c14a7e0
replace delegate with simple nested function
WalterBright Aug 12, 2022
6b01031
Update std/json.d
WalterBright Aug 12, 2022
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28 changes: 11 additions & 17 deletions std/json.d
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Original file line number Diff line number Diff line change
Expand Up @@ -1537,19 +1537,15 @@ if (isOutputRange!(Out,char))
toStringImpl!char(str);
}

// recursive @safe inference is broken here
// workaround: if json.put is @safe, we should be too,
// so annotate the recursion as @safe manually
static if (isSafe!({ json.put(""); }))
{
void delegate(ref const JSONValue, ulong) @safe toValue;
}
else
{
void delegate(ref const JSONValue, ulong) @system toValue;
}
/* make the function infer @system when json.put() is @system
*/
if (0)
json.put(' ');

void toValueImpl(ref const JSONValue value, ulong indentLevel)
/* Mark as @trusted because json.put() may be @system. This has difficulty
* inferring @safe because it is recursive.
*/
void toValueImpl(ref const JSONValue value, ulong indentLevel) @trusted
{
void putTabs(ulong additionalIndent = 0)
{
Expand Down Expand Up @@ -1594,7 +1590,7 @@ if (isOutputRange!(Out,char))
json.put(':');
if (pretty)
json.put(' ');
toValue(member, indentLevel + 1);
toValueImpl(member, indentLevel + 1);
}
}

Expand Down Expand Up @@ -1631,7 +1627,7 @@ if (isOutputRange!(Out,char))
if (i)
putCharAndEOL(',');
putTabs(1);
toValue(el, indentLevel + 1);
toValueImpl(el, indentLevel + 1);
}
putEOL();
putTabs();
Expand Down Expand Up @@ -1710,9 +1706,7 @@ if (isOutputRange!(Out,char))
}
}

toValue = &toValueImpl;

toValue(root, 0);
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To prevent adding a safety hole in toJSON, I suggest adding something like this outside of toValueImpl:

// Make the function infer `@system` when `json.put` is `@system`
if (0) json.put(' ');

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I'm not sure how this improves anything.

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Surely this shouldn't compile:

struct Sink {
    void put(char c) @system
    {
        *(cast(int*) 0xDEADBEEF) = 0;
    }
}

void main() @safe
{
    Sink s;
    auto jv = JSONValue("x");
    toJson(s, jv);
}

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A function that takes a template OutputRange cannot be invariably @trusted, that's in violation of safe interfaces.

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All right, but I dislike doing kludges like this. At least it's not as bad as the delegate kludge being replaced.

toValueImpl(root, 0);
}

// https://issues.dlang.org/show_bug.cgi?id=12897
Expand Down