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Error out on extraneous visitors.

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This commit is contained in:
Sönke Ludwig 2019-02-22 11:14:56 +01:00
parent 194e0dca41
commit 59826ad719
1 changed files with 88 additions and 21 deletions
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109
source/taggedalgebraic/taggedunion.d
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@ -350,7 +350,7 @@ template visit(VISITORS...) {
alias T = void;
else alias T = TU.FieldTypes[k];
alias h = selectHandler!(T, VISITORS);
static if (is(h == void)) static assert(false, "No handler is able to take type "~T.stringof);
static if (is(typeof(h) == typeof(null))) static assert(false, "No visitor defined for type type "~T.stringof);
else static if (is(typeof(h) == string)) static assert(false, h);
else static if (is(T == void)) return h();
else return h(tu.get!k);
@ -381,6 +381,34 @@ unittest {
assert(tu.visit!((v) => to!int(v)) == 43);
}
unittest {
union U {
Void none;
int count;
float length;
}
TaggedUnion!U u;
//
static assert(is(typeof(u.visit!((int) {}, (float) {}, () {}))));
u.visit!((_) {}, () {});
static assert(is(typeof(u.visit!((_) {}, () {}))));
static assert(is(typeof(u.visit!((_) {}, (float) {}, () {}))));
static assert(is(typeof(u.visit!((float) {}, (_) {}, () {}))));
static assert(!is(typeof(u.visit!((_) {})))); // missing void handler
static assert(!is(typeof(u.visit!(() {})))); // missing value handler
static assert(!is(typeof(u.visit!((_) {}, () {}, (string) {})))); // invalid typed handler
static assert(!is(typeof(u.visit!((int) {}, (float) {}, () {}, () {})))); // duplicate void handler
static assert(!is(typeof(u.visit!((_) {}, () {}, (_) {})))); // duplicate generic handler
static assert(!is(typeof(u.visit!((int) {}, (float) {}, (float) {}, () {})))); // duplicate typed handler
// TODO: error out for superfluous generic handlers
//static assert(!is(typeof(u.visit!((int) {}, (float) {}, () {}, (_) {})))); // superfluous generic handler
}
// workaround for "template to is not defined" error in the unit test above
// happens on DMD 2.080 and below
private U to(U, T)(T val) {
@ -405,7 +433,7 @@ template tryVisit(VISITORS...) {
alias T = void;
else alias T = TU.FieldTypes[k];
alias h = selectHandler!(T, VISITORS);
static if (is(h == void)) throw new Exception("Type "~T.stringof~" not handled by any visitor.");
static if (is(typeof(h) == typeof(null))) throw new Exception("Type "~T.stringof~" not handled by any visitor.");
else static if (is(typeof(h) == string)) static assert(false, h);
else static if (is(T == void)) return h();
else return h(tu.get!k);
@ -432,34 +460,73 @@ unittest {
enum isUnionType(T) = is(T == Void) || is(T == void) || is(T == typeof(null));
private template validateHandlers(TU, VISITORS...)
{
alias Types = TU.FieldTypes;
static foreach (int i; 0 .. VISITORS.length) {
static assert(anySatisfy!(matchesType!(VISITORS[i]), Types),
"Visitor at index "~i.stringof~" does not match any type of "~TU.stringof);
}
}
private template matchesType(alias fun, T)
{
static if (isSomeFunction!fun) {
alias Params = ParameterTypeTuple!fun;
static if (Params.length == 0 && is(T == void)) enum matchesType = true;
else static if (Params.length == 1 && is(T == Params[0])) enum matchesType = true;
else enum matchesType = false;
} else static if (!is(T == void)) {
static if (isSomeFunction!(fun!T)) {
alias Parms = ParameterTypeTuple!fun;
static if (Params.length == 1 && is(T == Params[0])) enum matchesType = true;
else enum matchesType = false;
} else enum matchesType = false;
} else enum matchesType = false;
}
private template selectHandler(T, VISITORS...)
{
import std.traits : ParameterTypeTuple, isSomeFunction;
// TODO: error out for ambiguous handlers and handlers that don't match any type!
template impl(int i) {
template typedIndex(int i, int matched_index = -1) {
static if (i < VISITORS.length) {
alias fun = VISITORS[i];
static if (isSomeFunction!fun) {
alias Params = ParameterTypeTuple!fun;
static if (Params.length == 0) {
static if (is(T == void))
alias impl = fun;
else alias impl = impl!(i+1);
} else static if (Params.length == 1) {
static if (is(T : Params[0]))
alias impl = fun;
else alias impl = impl!(i+1);
} else enum impl = "Visitor at index "~i.stringof~" must not take more than one parameter.";
} else static if (isSomeFunction!(fun!T)) {
static if (ParameterTypeTuple!(fun!T).length == 1)
alias impl = fun!T;
else enum impl = "Generic visitor at index "~i.stringof~" must have a single parameter.";
} else enum impl = "Visitor at index "~i.stringof~" (or its template instantiation with type "~T.stringof~") must be a valid function or delegate.";
} else alias impl = void;
static if (Params.length > 1) enum typedIndex = "Visitor at index "~i.stringof~" must not take more than one parameter.";
else static if (Params.length == 0 && is(T == void) || Params.length == 1 && is(T == Params[0])) {
static if (matched_index >= 0) enum typedIndex = "Vistor at index "~i.stringof~" conflicts with visitor at index "~matched_index~".";
else enum typedIndex = typedIndex!(i+1, i);
} else enum typedIndex = typedIndex!(i+1, matched_index);
} else enum typedIndex = typedIndex!(i+1, matched_index);
} else enum typedIndex = matched_index;
}
alias selectHandler = impl!0;
template genericIndex(int i, int matched_index = -1) {
static if (i < VISITORS.length) {
alias fun = VISITORS[i];
static if (!isSomeFunction!fun) {
static if (isSomeFunction!(fun!T)) {
static if (ParameterTypeTuple!(fun!T).length == 1) {
static if (matched_index >= 0) enum genericIndex = "Only one generic visitor allowed";
else enum genericIndex = genericIndex!(i+1, i);
} else enum genericIndex = "Generic visitor at index "~i.stringof~" must have a single parameter.";
} else enum genericIndex = "Visitor at index "~i.stringof~" (or its template instantiation with type "~T.stringof~") must be a valid function or delegate.";
} else enum genericIndex = genericIndex!(i+1, matched_index);
} else enum genericIndex = matched_index;
}
enum typed_index = typedIndex!0;
static if (is(T == void)) enum generic_index = -1;
else enum generic_index = genericIndex!0;
static if (is(typeof(typed_index) == string)) enum selectHandler = typed_index;
else static if (is(typeof(generic_index == string))) enum selectHandler = generic_index;
else static if (typed_index >= 0) alias selectHandler = VISITORS[typed_index];
else static if (generic_index >= 0) alias selectHandler = VISITORS[generic_index];
else enum selectHandler = null;
}
private string pascalCase(string camel_case)