Fix dues to crash when converting a const vector to another vector #1864.

releasenotes.md

@@ -14,6 +14,7 @@
 - Const strings and bytes were not properly converted to compile time bools.
 - Concatenating a const empty slice with another array caused a null pointer access.
 - Fix `linux-crt` and `linux-crtbegin` not getting recognized as a project paramater
+- Fix dues to crash when converting a const vector to another vector #1864.
 
 ### Stdlib changes
 - Added '%h' and '%H' for printing out binary data in hexadecimal using the formatter.

src/compiler/sema_casts.c

@@ -1286,11 +1286,20 @@ static bool rule_vec_to_vec(CastContext *cc, bool is_explicit, bool is_silent)
 {
 	if (cc->from->array.len != cc->to->array.len) return sema_cast_error(cc, false, is_silent);
 	Type *from_base = cc->from->array.base;
+	CastContext cc_copy = *cc;
 	cast_context_set_to(cc, cc->to->array.base);
 	// Allow bool vectors to expand to any int.
 	if (from_base == type_bool && cc->to_group == CONV_INT) return true;
+	// Create a fake expression that can't be folded for some checking if the
+	// the elements could be cast.
+	Expr temp = { .expr_kind = EXPR_EXPR_BLOCK, .type = from_base, .span = cc->expr->span, .resolve_status = RESOLVE_DONE };
+	cc->expr = &temp;
 	cast_context_set_from(cc, from_base);
-	return cast_is_allowed(cc, is_explicit, is_silent);
+	bool success = cast_is_allowed(cc, is_explicit, true);
+	*cc = cc_copy;
+	if (is_silent) return success;
+	if (success) return true;
+	return sema_cast_error(cc, is_explicit ? false : rule_vec_to_vec(cc, true, true), false);
 }
 
 static bool rule_expand_to_vec(CastContext *cc, bool is_explicit, bool is_silent)

test/test_suite/vector/vector_to_array_fail.c3

@@ -9,5 +9,5 @@ fn void main()
 	int[<*>] z = x;
 	int[<*>] w = y;
 	double[<2>] ww = x;
-	short[<2>] www = y; // #error: implicitly be converted
+	short[<2>] www = y; // #error: Implicitly casting 'int[2]' to 'short[<2>]'
 }

test/test_suite/vector/vector_to_vector_const_fail.c3

@@ -0,0 +1,5 @@
+fn int main(String[] args)
+{
+	const double[4] ONE = { 1.0, 1.0, 1.0, 1.0 };
+	float[<4>] vec4 = ONE; // #error: Implicitly casting 'double[4]' to 'float[<4>]'
+}