build: separate package identity from storage paths

selfhost/cmd/w6c/main.ww

@@ -60,6 +60,25 @@ fn slurp(path: *u8) (*u8, u64) = {
 	return buf.ptr, nz;
 };
 
+fn exportownermatches(buf: *u8, n: u64, path: *u8) bool = {
+	let prefix: str = "//ww:module ";
+	let pn: u64 = cstrlen(path);
+	let poff: u64 = prefix.len: u64;
+	let need: u64 = poff + pn + 1u64;
+	if (n < need) { return false; };
+	let i: u64 = 0u64;
+	for (i < poff) {
+		if (buf[i] != prefix.ptr[i]) { return false; };
+		i += 1u64;
+	};
+	i = 0u64;
+	for (i < pn) {
+		if (buf[poff + i] != path[i]) { return false; };
+		i += 1u64;
+	};
+	return buf[need - 1u64] == 10u8;
+};
+
 export fn main(argc: i32, argv: **u8) i32 = {
 	let src: *u8 = nil;
 	let out: *u8 = nil;
@@ -204,6 +223,17 @@ export fn main(argc: i32, argv: **u8) i32 = {
 			os.write(2, nl.ptr, nl.len: u64);
 			return 1;
 		};
+		if (!exportownermatches(ibuf, ilen, importpaths[importi])) {
+			let pre: str = "w6c: import ";
+			let mid: str = ": export owner mismatch in ";
+			let nl: str = "\n";
+			os.write(2, pre.ptr, pre.len: u64);
+			os.write(2, importpaths[importi], cstrlen(importpaths[importi]));
+			os.write(2, mid.ptr, mid.len: u64);
+			os.write(2, importfiles[importi], cstrlen(importfiles[importi]));
+			os.write(2, nl.ptr, nl.len: u64);
+			return 1;
+		};
 		let il: lex;
 		lexinit(&il, strings.dup(pathstr(importfiles[importi])), ibuf, ilen);
 		let ips: parser;