Support alt-registry names in [patch] table.

src/cargo/util/toml/mod.rs

@@ -1205,7 +1205,13 @@ impl TomlManifest {
         for (url, deps) in self.patch.iter().flat_map(|x| x) {
             let url = match &url[..] {
                 CRATES_IO_REGISTRY => CRATES_IO_INDEX.parse().unwrap(),
-                _ => url.to_url()?,
+                _ => cx
+                    .config
+                    .get_registry_index(url)
+                    .or_else(|_| url.to_url())
+                    .chain_err(|| {
+                        format!("[patch] entry `{}` should be a URL or registry name", url)
+                    })?,
             };
             patch.insert(
                 url,

tests/testsuite/alt_registry.rs

@@ -514,3 +514,47 @@ fn passwords_in_url_forbidden() {
         .with_stderr_contains("error: Registry URLs may not contain passwords")
         .run();
 }
+
+#[test]
+fn patch_alt_reg() {
+    Package::new("bar", "0.1.0").publish();
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["alternative-registries"]
+
+            [package]
+            name = "foo"
+            version = "0.0.1"
+
+            [dependencies]
+            bar = { version = "0.1.0", registry = "alternative" }
+
+            [patch.alternative]
+            bar = { path = "bar" }
+        "#,
+        )
+        .file(
+            "src/lib.rs",
+            "
+            extern crate bar;
+            pub fn f() { bar::bar(); }
+            ",
+        )
+        .file("bar/Cargo.toml", &basic_manifest("bar", "0.1.0"))
+        .file("bar/src/lib.rs", "pub fn bar() {}")
+        .build();
+
+    p.cargo("build")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[UPDATING] `[ROOT][..]` index
+[COMPILING] bar v0.1.0 ([CWD]/bar)
+[COMPILING] foo v0.0.1 ([CWD])
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+}

tests/testsuite/patch.rs

@@ -734,6 +734,9 @@ fn non_crates_io() {
             "\
 error: failed to parse manifest at `[..]`
 
+Caused by:
+  [patch] entry `some-other-source` should be a URL or registry name
+
 Caused by:
   invalid url `some-other-source`: relative URL without a base
 ",