ww: add file-scoped import aliases

cmd/wcc/parse.c

@@ -1315,30 +1315,40 @@ parseblock(Parser *p)
 	return n;
 }
 
-/* `import encoding.utf8;` — the driver resolves the dotted path to a
- * directory; the checker only needs the leaf (`utf8`) as the module
- * bareword for n_use→decl disambiguation, mirroring Hare's
- * `use encoding::utf8;` → `utf8::name` (ref/hare/hare/ast/import.ha:7
- * stores `ident: []str` but identifier-resolution uses the last
- * component). */
+/* The optional alias is source-local; the dotted path remains the dependency
+ * identity supplied to the package driver. */
 static Node *
 parseuse(Parser *p)
 {
 	Pos pp = p->cur.pos;
 	expect(p, TK_USE);
 	Node *n = newnode(p->a, N_USE, pp);
-	/* M1 #22: accumulate the full dotted import path in usepath. `str`
-	 * starts as its leaf; direct export metadata later installs the imported
-	 * declaration's default name without changing canonical identity. */
-	const char *leaf = expectident(p);
+	const char *alias = NULL;
+	const char *first;
+	if (p->cur.kind == TK_UNDER) {
+		errorf(p->cur.pos, "blank import alias _ is not implemented");
+		p->errs++;
+		alias = "_";
+		advance(p);
+		first = expectident(p);
+	} else {
+		first = expectident(p);
+		if (p->cur.kind == TK_IDENT) {
+			alias = first;
+			first = expectident(p);
+		}
+	}
+	const char *leaf = first;
 	const char *path = leaf;
 	while (accept(p, TK_DOT)) {
 		leaf = expectident(p);
 		path = aprintf(p->a, "%s.%s", path, leaf);
 	}
-	n->str = leaf;
-	n->strlen = strlen(leaf);
+	n->str = alias ? alias : leaf;
+	n->strlen = strlen(n->str);
+	n->usesource = path;
 	n->usepath = path;
+	n->usealias = alias;
 	expect(p, TK_SEMI);
 	return n;
 }