compiler: support package test runtime aliases

lib/ww/syntax/parse.ww

@@ -46,6 +46,9 @@ export type parser = struct {
 	// rule stay intact), and the in-file `package` clause asserts (leaf ==
 	// last component) instead of overwriting curmod. "" means inactive.
 	resetmod: str,
+	// Hidden package-driver alias for the toolchain `package test` source.
+	// Empty outside that one separate-compilation edge.
+	testmodule: str,
 };
 
 fn refill(p: *parser) void = {
@@ -67,6 +70,7 @@ export fn parserinit(p: *parser, l: *lex) void = {
 	p.nocast = 0;
 	p.pathmod = "";
 	p.resetmod = "";
+	p.testmodule = "";
 	refill(p);
 };
 
@@ -611,7 +615,11 @@ export fn parsefile(p: *parser) *node = {
 				let (pre, post) = strings.rcut(active, ".");
 				let last: str = post;
 				if (post.len == 0) { last = active; };
-				if (strings.compare(name, last) != 0) {
+				let testsupport: bool = strings.compare(
+					p.testmodule, "__wwtest") == 0
+					&& strings.compare(active, "__wwtest") == 0
+					&& strings.compare(name, "test") == 0;
+				if (strings.compare(name, last) != 0 && !testsupport) {
 					errmsg(p, "package does not match import path");
 				};
 			} else {