Fix not freeing a zero length String

lib/std/core/string.c3

@@ -526,6 +526,11 @@ fn String String.tconcat(s1, String s2) => s1.concat(s2, allocator::temp());
 
 fn ZString String.zstr_tcopy(s) => s.zstr_copy(allocator::temp()) @inline;
 
+<*
+ Copy this string, by duplicating the string, always adding a zero byte
+ sentinel, so that it safely can be converted to a ZString by a
+ cast.
+*>
 fn String String.copy(s, Allocator allocator = allocator::heap())
 {
 	usz len = s.len;
@@ -537,7 +542,7 @@ fn String String.copy(s, Allocator allocator = allocator::heap())
 
 fn void String.free(&s, Allocator allocator = allocator::heap())
 {
-	if (!s.len) return;
+	if (!s.ptr) return;
 	allocator::free(allocator, s.ptr);
 	*s = "";
 }

releasenotes.md

@@ -55,6 +55,7 @@
 - Assert on certain slice to slice casts. #1768.
 - Fix vector float -> bool conversion.
 - Fix `+a = 1` erronously being accepted.
+- Fix not freeing a zero length String
 
 ### Stdlib changes
 - Increase BitWriter.write_bits limit up to 32 bits.

src/compiler/llvm_codegen_expr.c

@@ -3083,7 +3083,6 @@ static void gencontext_emit_slice(GenContext *c, BEValue *be_value, Expr *expr)
 	llvm_value_rvalue(c, &start);
 	llvm_value_rvalue(c, &end);
 
-
 	// Calculate the size
 	LLVMValueRef size;
 	if (is_exclusive)
@@ -3268,11 +3267,7 @@ static void llvm_emit_slice_assign(GenContext *c, BEValue *be_value, Expr *expr)
 	llvm_emit_br(c, cond_block);
 
 	// Finally set up our phi
-	if (!assign_block_end)
-	{
-		offset = start.value;
-	}
-	else
+	if (assign_block_end)
 	{
 		llvm_set_phi(offset, start.value, start_block, next_offset, assign_block_end);
 	}