Support incremental in compiletest for non-incremental modes.

src/test/codegen-units/partitioning/extern-drop-glue.rs

@@ -1,9 +1,10 @@
 //
 
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
 // We specify opt-level=0 because `drop_in_place` is `Internal` when optimizing
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/extern-drop-glue
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus -Copt-level=0
 
 #![allow(dead_code)]

src/test/codegen-units/partitioning/extern-generic.rs

@@ -1,7 +1,8 @@
 //
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=eager -Cincremental=tmp/partitioning-tests/extern-generic -Zshare-generics=y
+// incremental
+// compile-flags:-Zprint-mono-items=eager -Zshare-generics=y
 
 #![allow(dead_code)]
 #![crate_type="lib"]

src/test/codegen-units/partitioning/incremental-merging.rs

@@ -1,6 +1,7 @@
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/incremental-merging
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Ccodegen-units=3
 
 #![crate_type = "rlib"]

src/test/codegen-units/partitioning/inlining-from-extern-crate.rs

@@ -1,7 +1,8 @@
 //
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/inlining-from-extern-crate
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus
 
 #![crate_type="lib"]

src/test/codegen-units/partitioning/local-drop-glue.rs

@@ -1,8 +1,9 @@
 //
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
 // We specify opt-level=0 because `drop_in_place` is `Internal` when optimizing
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/local-drop-glue
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus -Copt-level=0
 
 #![allow(dead_code)]

src/test/codegen-units/partitioning/local-generic.rs

@@ -1,6 +1,7 @@
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=eager -Cincremental=tmp/partitioning-tests/local-generic
+// incremental
+// compile-flags:-Zprint-mono-items=eager
 
 #![allow(dead_code)]
 #![crate_type="lib"]

src/test/codegen-units/partitioning/local-inlining-but-not-all.rs

@@ -1,7 +1,8 @@
 //
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/local-inlining-but-not-all
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus=no
 
 #![allow(dead_code)]

src/test/codegen-units/partitioning/local-inlining.rs

@@ -1,7 +1,8 @@
 //
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/local-inlining
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus
 
 #![allow(dead_code)]

src/test/codegen-units/partitioning/local-transitive-inlining.rs

@@ -1,7 +1,8 @@
 //
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/local-transitive-inlining
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus
 
 #![allow(dead_code)]

src/test/codegen-units/partitioning/methods-are-with-self-type.rs

@@ -4,9 +4,10 @@
 // ignore-test
 
 //
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/methods-are-with-self-type
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 
 #![allow(dead_code)]
 #![feature(start)]

src/test/codegen-units/partitioning/regular-modules.rs

@@ -1,6 +1,7 @@
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=eager -Cincremental=tmp/partitioning-tests/regular-modules
+// incremental
+// compile-flags:-Zprint-mono-items=eager
 
 #![allow(dead_code)]
 #![crate_type="lib"]

src/test/codegen-units/partitioning/shared-generics.rs

@@ -2,7 +2,8 @@
 // no-prefer-dynamic
 // NOTE: We always compile this test with -Copt-level=0 because higher opt-levels
 //       prevent drop-glue from participating in share-generics.
-// compile-flags:-Zprint-mono-items=eager -Zshare-generics=yes -Cincremental=tmp/partitioning-tests/shared-generics-exe -Copt-level=0
+// incremental
+// compile-flags:-Zprint-mono-items=eager -Zshare-generics=yes -Copt-level=0
 
 #![crate_type="rlib"]
 

src/test/codegen-units/partitioning/statics.rs

@@ -1,6 +1,7 @@
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/statics
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 
 #![crate_type="rlib"]
 

src/test/codegen-units/partitioning/vtable-through-const.rs

@@ -1,8 +1,9 @@
 //
 
-// We specify -C incremental here because we want to test the partitioning for
+// We specify incremental here because we want to test the partitioning for
 // incremental compilation
-// compile-flags:-Zprint-mono-items=lazy -Cincremental=tmp/partitioning-tests/vtable-through-const
+// incremental
+// compile-flags:-Zprint-mono-items=lazy
 // compile-flags:-Zinline-in-all-cgus
 
 // This test case makes sure, that references made through constants are

src/test/ui/associated-type-bounds/traits-assoc-type-macros.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags:-Cincremental=tmp/traits-assoc-type-macros
+// incremental
 
 // This test case makes sure that we can compile with incremental compilation
 // enabled when there are macros, traits, inheritance and associated types involved.

src/test/ui/async-await/issue-72442.rs

@@ -1,5 +1,5 @@
 // edition:2018
-// compile-flags:-Cincremental=tmp/issue-72442
+// incremental
 
 use std::fs::File;
 use std::future::Future;

src/test/ui/async-await/issues/issue-64964.rs

@@ -1,5 +1,6 @@
 // check-pass
-// compile-flags: -Z query-dep-graph -C incremental=tmp/issue-64964
+// incremental
+// compile-flags: -Z query-dep-graph
 // edition:2018
 
 // Regression test for ICE related to `await`ing in a method + incr. comp. (#64964)

src/test/ui/dep-graph/dep-graph-assoc-type-codegen.rs

@@ -1,7 +1,8 @@
 // Test that when a trait impl changes, fns whose body uses that trait
 // must also be recompiled.
 
-// compile-flags: -Z query-dep-graph -C incremental=tmp/dep-graph-assoc-type-codegen
+// incremental
+// compile-flags: -Z query-dep-graph
 
 #![feature(rustc_attrs)]
 #![allow(warnings)]

src/test/ui/dep-graph/dep-graph-assoc-type-codegen.stderr

@@ -1,5 +1,5 @@
 error: OK
-  --> $DIR/dep-graph-assoc-type-codegen.rs:28:5
+  --> $DIR/dep-graph-assoc-type-codegen.rs:29:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/dep-graph/dep-graph-caller-callee.rs

@@ -1,7 +1,8 @@
 // Test that immediate callers have to change when callee changes, but
 // not callers' callers.
 
-// compile-flags: -Z query-dep-graph -C incremental=tmp/dep-graph-caller-callee
+// incremental
+// compile-flags: -Z query-dep-graph
 
 #![feature(rustc_attrs)]
 #![allow(dead_code)]

src/test/ui/dep-graph/dep-graph-caller-callee.stderr

@@ -1,11 +1,11 @@
 error: OK
-  --> $DIR/dep-graph-caller-callee.rs:20:5
+  --> $DIR/dep-graph-caller-callee.rs:21:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `x` to `typeck`
-  --> $DIR/dep-graph-caller-callee.rs:31:5
+  --> $DIR/dep-graph-caller-callee.rs:32:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/dep-graph/dep-graph-struct-signature.rs

@@ -1,7 +1,8 @@
 // Test cases where a changing struct appears in the signature of fns
 // and methods.
 
-// compile-flags: -Z query-dep-graph -C incremental=tmp/dep-graph-struct-signature
+// incremental
+// compile-flags: -Z query-dep-graph
 
 #![feature(rustc_attrs)]
 #![allow(dead_code)]

src/test/ui/dep-graph/dep-graph-struct-signature.stderr

@@ -1,29 +1,23 @@
 error: no path from `WillChange` to `type_of`
-  --> $DIR/dep-graph-struct-signature.rs:27:5
+  --> $DIR/dep-graph-struct-signature.rs:28:5
    |
 LL |     #[rustc_then_this_would_need(type_of)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `WillChange` to `associated_item`
-  --> $DIR/dep-graph-struct-signature.rs:28:5
+  --> $DIR/dep-graph-struct-signature.rs:29:5
    |
 LL |     #[rustc_then_this_would_need(associated_item)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `WillChange` to `trait_def`
-  --> $DIR/dep-graph-struct-signature.rs:29:5
+  --> $DIR/dep-graph-struct-signature.rs:30:5
    |
 LL |     #[rustc_then_this_would_need(trait_def)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-struct-signature.rs:31:9
-   |
-LL |         #[rustc_then_this_would_need(fn_sig)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: OK
-  --> $DIR/dep-graph-struct-signature.rs:35:5
+  --> $DIR/dep-graph-struct-signature.rs:32:9
    |
 LL |         #[rustc_then_this_would_need(fn_sig)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -31,101 +25,107 @@ LL |     #[rustc_then_this_would_need(fn_sig)]
 error: OK
   --> $DIR/dep-graph-struct-signature.rs:36:5
    |
-LL |     #[rustc_then_this_would_need(typeck)]
+LL |     #[rustc_then_this_would_need(fn_sig)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-struct-signature.rs:39:5
+  --> $DIR/dep-graph-struct-signature.rs:37:5
    |
-LL |     #[rustc_then_this_would_need(fn_sig)]
+LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
   --> $DIR/dep-graph-struct-signature.rs:40:5
    |
+LL |     #[rustc_then_this_would_need(fn_sig)]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: OK
+  --> $DIR/dep-graph-struct-signature.rs:41:5
+   |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-struct-signature.rs:45:5
+  --> $DIR/dep-graph-struct-signature.rs:46:5
    |
 LL |     #[rustc_then_this_would_need(type_of)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: OK
-  --> $DIR/dep-graph-struct-signature.rs:47:9
-   |
-LL |         #[rustc_then_this_would_need(fn_sig)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error: OK
   --> $DIR/dep-graph-struct-signature.rs:48:9
    |
+LL |         #[rustc_then_this_would_need(fn_sig)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: OK
+  --> $DIR/dep-graph-struct-signature.rs:49:9
+   |
 LL |         #[rustc_then_this_would_need(typeck)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-struct-signature.rs:52:5
+  --> $DIR/dep-graph-struct-signature.rs:53:5
    |
 LL |     #[rustc_then_this_would_need(type_of)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: OK
-  --> $DIR/dep-graph-struct-signature.rs:54:9
-   |
-LL |         #[rustc_then_this_would_need(fn_sig)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error: OK
   --> $DIR/dep-graph-struct-signature.rs:55:9
    |
+LL |         #[rustc_then_this_would_need(fn_sig)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: OK
+  --> $DIR/dep-graph-struct-signature.rs:56:9
+   |
 LL |         #[rustc_then_this_would_need(typeck)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-struct-signature.rs:60:9
+  --> $DIR/dep-graph-struct-signature.rs:61:9
    |
 LL |         #[rustc_then_this_would_need(type_of)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-struct-signature.rs:62:9
+  --> $DIR/dep-graph-struct-signature.rs:63:9
    |
 LL |         #[rustc_then_this_would_need(type_of)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `WillChange` to `type_of`
-  --> $DIR/dep-graph-struct-signature.rs:67:5
+  --> $DIR/dep-graph-struct-signature.rs:68:5
    |
 LL |     #[rustc_then_this_would_need(type_of)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `WillChange` to `type_of`
-  --> $DIR/dep-graph-struct-signature.rs:74:5
+  --> $DIR/dep-graph-struct-signature.rs:75:5
    |
 LL |     #[rustc_then_this_would_need(type_of)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `WillChange` to `fn_sig`
-  --> $DIR/dep-graph-struct-signature.rs:76:9
+  --> $DIR/dep-graph-struct-signature.rs:77:9
    |
 LL |         #[rustc_then_this_would_need(fn_sig)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `WillChange` to `fn_sig`
-  --> $DIR/dep-graph-struct-signature.rs:80:5
+  --> $DIR/dep-graph-struct-signature.rs:81:5
    |
 LL |     #[rustc_then_this_would_need(fn_sig)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `WillChange` to `fn_sig`
-  --> $DIR/dep-graph-struct-signature.rs:83:5
+  --> $DIR/dep-graph-struct-signature.rs:84:5
    |
 LL |     #[rustc_then_this_would_need(fn_sig)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `WillChange` to `typeck`
-  --> $DIR/dep-graph-struct-signature.rs:84:5
+  --> $DIR/dep-graph-struct-signature.rs:85:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/dep-graph/dep-graph-trait-impl-two-traits-same-method.rs

@@ -1,7 +1,8 @@
 // Test that adding an impl to a trait `Foo` DOES affect functions
 // that only use `Bar` if they have methods in common.
 
-// compile-flags: -Z query-dep-graph -C incremental=tmp/dep-graph-trait-impl-two-traits-same-method
+// incremental
+// compile-flags: -Z query-dep-graph
 
 #![feature(rustc_attrs)]
 #![allow(dead_code)]

src/test/ui/dep-graph/dep-graph-trait-impl-two-traits-same-method.stderr

@@ -1,11 +1,11 @@
 error: OK
-  --> $DIR/dep-graph-trait-impl-two-traits-same-method.rs:32:5
+  --> $DIR/dep-graph-trait-impl-two-traits-same-method.rs:33:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `x::<impl Foo for u32>` to `typeck`
-  --> $DIR/dep-graph-trait-impl-two-traits-same-method.rs:41:5
+  --> $DIR/dep-graph-trait-impl-two-traits-same-method.rs:42:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/dep-graph/dep-graph-trait-impl-two-traits.rs

@@ -1,7 +1,8 @@
 // Test that adding an impl to a trait `Foo` does not affect functions
 // that only use `Bar`, so long as they do not have methods in common.
 
-// compile-flags: -Z query-dep-graph -C incremental=tmp/dep-graph-trait-impl-two-traits
+// incremental
+// compile-flags: -Z query-dep-graph
 
 #![feature(rustc_attrs)]
 #![allow(warnings)]

src/test/ui/dep-graph/dep-graph-trait-impl-two-traits.stderr

@@ -1,11 +1,11 @@
 error: no path from `x::<impl Foo for char>` to `typeck`
-  --> $DIR/dep-graph-trait-impl-two-traits.rs:31:5
+  --> $DIR/dep-graph-trait-impl-two-traits.rs:32:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `x::<impl Foo for char>` to `typeck`
-  --> $DIR/dep-graph-trait-impl-two-traits.rs:40:5
+  --> $DIR/dep-graph-trait-impl-two-traits.rs:41:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/dep-graph/dep-graph-trait-impl.rs

@@ -1,7 +1,8 @@
 // Test that when a trait impl changes, fns whose body uses that trait
 // must also be recompiled.
 
-// compile-flags: -Z query-dep-graph -C incremental=tmp/dep-graph-trait-impl
+// incremental
+// compile-flags: -Z query-dep-graph
 
 #![feature(rustc_attrs)]
 #![allow(warnings)]

src/test/ui/dep-graph/dep-graph-trait-impl.stderr

@@ -1,29 +1,29 @@
 error: OK
-  --> $DIR/dep-graph-trait-impl.rs:27:5
+  --> $DIR/dep-graph-trait-impl.rs:28:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-trait-impl.rs:32:5
+  --> $DIR/dep-graph-trait-impl.rs:33:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-trait-impl.rs:37:5
+  --> $DIR/dep-graph-trait-impl.rs:38:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-trait-impl.rs:42:5
+  --> $DIR/dep-graph-trait-impl.rs:43:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `x::<impl Foo for char>` to `typeck`
-  --> $DIR/dep-graph-trait-impl.rs:55:5
+  --> $DIR/dep-graph-trait-impl.rs:56:5
    |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/dep-graph/dep-graph-type-alias.rs

@@ -1,6 +1,7 @@
 // Test that changing what a `type` points to does not go unnoticed.
 
-// compile-flags: -Z query-dep-graph -C incremental=tmp/dep-graph-type-alias
+// incremental
+// compile-flags: -Z query-dep-graph
 
 #![feature(rustc_attrs)]
 #![allow(dead_code)]

src/test/ui/dep-graph/dep-graph-type-alias.stderr

@@ -1,71 +1,71 @@
 error: no path from `TypeAlias` to `type_of`
-  --> $DIR/dep-graph-type-alias.rs:17:1
+  --> $DIR/dep-graph-type-alias.rs:18:1
    |
 LL | #[rustc_then_this_would_need(type_of)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-type-alias.rs:19:5
+  --> $DIR/dep-graph-type-alias.rs:20:5
    |
 LL |     #[rustc_then_this_would_need(type_of)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `TypeAlias` to `type_of`
-  --> $DIR/dep-graph-type-alias.rs:24:1
+  --> $DIR/dep-graph-type-alias.rs:25:1
    |
 LL | #[rustc_then_this_would_need(type_of)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-type-alias.rs:27:9
+  --> $DIR/dep-graph-type-alias.rs:28:9
    |
 LL |         #[rustc_then_this_would_need(type_of)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `TypeAlias` to `type_of`
-  --> $DIR/dep-graph-type-alias.rs:33:1
+  --> $DIR/dep-graph-type-alias.rs:34:1
    |
 LL | #[rustc_then_this_would_need(type_of)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-type-alias.rs:35:5
+  --> $DIR/dep-graph-type-alias.rs:36:5
    |
 LL |     #[rustc_then_this_would_need(fn_sig)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: no path from `TypeAlias` to `type_of`
-  --> $DIR/dep-graph-type-alias.rs:41:1
+  --> $DIR/dep-graph-type-alias.rs:42:1
    |
 LL | #[rustc_then_this_would_need(type_of)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: OK
-  --> $DIR/dep-graph-type-alias.rs:43:5
-   |
-LL |     #[rustc_then_this_would_need(fn_sig)]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error: OK
   --> $DIR/dep-graph-type-alias.rs:44:5
    |
+LL |     #[rustc_then_this_would_need(fn_sig)]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: OK
+  --> $DIR/dep-graph-type-alias.rs:45:5
+   |
 LL |     #[rustc_then_this_would_need(typeck)]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-type-alias.rs:48:1
+  --> $DIR/dep-graph-type-alias.rs:49:1
    |
 LL | #[rustc_then_this_would_need(type_of)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-type-alias.rs:51:1
+  --> $DIR/dep-graph-type-alias.rs:52:1
    |
 LL | #[rustc_then_this_would_need(fn_sig)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: OK
-  --> $DIR/dep-graph-type-alias.rs:52:1
+  --> $DIR/dep-graph-type-alias.rs:53:1
    |
 LL | #[rustc_then_this_would_need(typeck)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/dep-graph/dep-graph-variance-alias.rs

@@ -1,7 +1,8 @@
 // Test that changing what a `type` points to does not go unnoticed
 // by the variance analysis.
 
-// compile-flags: -Z query-dep-graph -C incremental=tmp/dep-graph-variance-alias
+// incremental
+// compile-flags: -Z query-dep-graph
 
 #![feature(rustc_attrs)]
 #![allow(dead_code)]

src/test/ui/dep-graph/dep-graph-variance-alias.stderr

@@ -1,5 +1,5 @@
 error: OK
-  --> $DIR/dep-graph-variance-alias.rs:18:1
+  --> $DIR/dep-graph-variance-alias.rs:19:1
    |
 LL | #[rustc_then_this_would_need(variances_of)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/suggestions/issue-72766.rs

@@ -1,5 +1,5 @@
 // edition:2018
-// compile-flags: -Cincremental=tmp/issue-72766
+// incremental
 
 pub struct SadGirl;
 

src/test/ui/wf/hir-wf-check-erase-regions.rs

@@ -1,5 +1,5 @@
 // Regression test for #87549.
-// compile-flags: -C incremental=tmp/wf/hir-wf-check-erase-regions
+// incremental
 
 pub struct Table<T, const N: usize>([Option<T>; N]);
 

src/tools/compiletest/src/common.rs

@@ -459,3 +459,9 @@ pub fn output_base_dir(config: &Config, testpaths: &TestPaths, revision: Option<
 pub fn output_base_name(config: &Config, testpaths: &TestPaths, revision: Option<&str>) -> PathBuf {
     output_base_dir(config, testpaths, revision).join(testpaths.file.file_stem().unwrap())
 }
+
+/// Absolute path to the directory to use for incremental compilation. Example:
+///   /path/to/build/host-triple/test/ui/relative/testname.mode/testname.inc
+pub fn incremental_dir(config: &Config, testpaths: &TestPaths) -> PathBuf {
+    output_base_name(config, testpaths, None).with_extension("inc")
+}

src/tools/compiletest/src/header.rs

@@ -113,6 +113,21 @@ pub struct TestProps {
     // testing harness and used when generating compilation
     // arguments. (In particular, it propagates to the aux-builds.)
     pub incremental_dir: Option<PathBuf>,
+    // If `true`, this test will use incremental compilation.
+    //
+    // This can be set manually with the `incremental` header, or implicitly
+    // by being a part of an incremental mode test. Using the `incremental`
+    // header should be avoided if possible; using an incremental mode test is
+    // preferred. Incremental mode tests support multiple passes, which can
+    // verify that the incremental cache can be loaded properly after being
+    // created. Just setting the header will only verify the behavior with
+    // creating an incremental cache, but doesn't check that it is created
+    // correctly.
+    //
+    // Compiletest will create the incremental directory, and ensure it is
+    // empty before the test starts. Incremental mode tests will reuse the
+    // incremental directory between passes in the same test.
+    pub incremental: bool,
     // How far should the test proceed while still passing.
     pass_mode: Option<PassMode>,
     // Ignore `--pass` overrides from the command line for this test.
@@ -163,6 +178,7 @@ impl TestProps {
             pretty_compare_only: false,
             forbid_output: vec![],
             incremental_dir: None,
+            incremental: false,
             pass_mode: None,
             fail_mode: None,
             ignore_pass: false,
@@ -350,6 +366,10 @@ impl TestProps {
                 if !self.stderr_per_bitwidth {
                     self.stderr_per_bitwidth = config.parse_stderr_per_bitwidth(ln);
                 }
+
+                if !self.incremental {
+                    self.incremental = config.parse_incremental(ln);
+                }
             });
         }
 
@@ -360,6 +380,10 @@ impl TestProps {
             self.failure_status = 101;
         }
 
+        if config.mode == Mode::Incremental {
+            self.incremental = true;
+        }
+
         for key in &["RUST_TEST_NOCAPTURE", "RUST_TEST_THREADS"] {
             if let Ok(val) = env::var(key) {
                 if self.exec_env.iter().find(|&&(ref x, _)| x == key).is_none() {
@@ -731,6 +755,10 @@ impl Config {
     fn parse_edition(&self, line: &str) -> Option<String> {
         self.parse_name_value_directive(line, "edition")
     }
+
+    fn parse_incremental(&self, line: &str) -> bool {
+        self.parse_name_directive(line, "incremental")
+    }
 }
 
 fn expand_variables(mut value: String, config: &Config) -> String {

src/tools/compiletest/src/runtest.rs

@@ -1,7 +1,7 @@
 // ignore-tidy-filelength
 
 use crate::common::{expected_output_path, UI_EXTENSIONS, UI_FIXED, UI_STDERR, UI_STDOUT};
-use crate::common::{output_base_dir, output_base_name, output_testname_unique};
+use crate::common::{incremental_dir, output_base_dir, output_base_name, output_testname_unique};
 use crate::common::{Assembly, Incremental, JsDocTest, MirOpt, RunMake, RustdocJson, Ui};
 use crate::common::{Codegen, CodegenUnits, DebugInfo, Debugger, Rustdoc};
 use crate::common::{CompareMode, FailMode, PassMode};
@@ -229,18 +229,24 @@ pub fn run(config: Config, testpaths: &TestPaths, revision: Option<&str>) {
         print!("\n\n");
     }
     debug!("running {:?}", testpaths.file.display());
-    let props = TestProps::from_file(&testpaths.file, revision, &config);
+    let mut props = TestProps::from_file(&testpaths.file, revision, &config);
+    if props.incremental {
+        props.incremental_dir = Some(incremental_dir(&config, testpaths));
+    }
 
     let cx = TestCx { config: &config, props: &props, testpaths, revision };
     create_dir_all(&cx.output_base_dir()).unwrap();
+    if props.incremental {
+        cx.init_incremental_test();
+    }
 
     if config.mode == Incremental {
         // Incremental tests are special because they cannot be run in
         // parallel.
         assert!(!props.revisions.is_empty(), "Incremental tests require revisions.");
-        cx.init_incremental_test();
         for revision in &props.revisions {
-            let revision_props = TestProps::from_file(&testpaths.file, Some(revision), &config);
+            let mut revision_props = TestProps::from_file(&testpaths.file, Some(revision), &config);
+            revision_props.incremental_dir = props.incremental_dir.clone();
             let rev_cx = TestCx {
                 config: &config,
                 props: &revision_props,
@@ -2937,7 +2943,7 @@ impl<'test> TestCx<'test> {
         // incremental workproduct directory.  Delete any old
         // incremental work products that may be there from prior
         // runs.
-        let incremental_dir = self.incremental_dir();
+        let incremental_dir = self.props.incremental_dir.as_ref().unwrap();
         if incremental_dir.exists() {
             // Canonicalizing the path will convert it to the //?/ format
             // on Windows, which enables paths longer than 260 character
@@ -2947,7 +2953,7 @@ impl<'test> TestCx<'test> {
         fs::create_dir_all(&incremental_dir).unwrap();
 
         if self.config.verbose {
-            print!("init_incremental_test: incremental_dir={}", incremental_dir.display());
+            println!("init_incremental_test: incremental_dir={}", incremental_dir.display());
         }
     }
 
@@ -2974,46 +2980,30 @@ impl<'test> TestCx<'test> {
         let revision = self.revision.expect("incremental tests require a list of revisions");
 
         // Incremental workproduct directory should have already been created.
-        let incremental_dir = self.incremental_dir();
+        let incremental_dir = self.props.incremental_dir.as_ref().unwrap();
         assert!(incremental_dir.exists(), "init_incremental_test failed to create incremental dir");
 
-        // Add an extra flag pointing at the incremental directory.
-        let mut revision_props = self.props.clone();
-        revision_props.incremental_dir = Some(incremental_dir);
-
-        let revision_cx = TestCx {
-            config: self.config,
-            props: &revision_props,
-            testpaths: self.testpaths,
-            revision: self.revision,
-        };
-
         if self.config.verbose {
-            print!("revision={:?} revision_props={:#?}", revision, revision_props);
+            print!("revision={:?} props={:#?}", revision, self.props);
         }
 
         if revision.starts_with("rpass") {
-            if revision_cx.props.should_ice {
-                revision_cx.fatal("can only use should-ice in cfail tests");
+            if self.props.should_ice {
+                self.fatal("can only use should-ice in cfail tests");
             }
-            revision_cx.run_rpass_test();
+            self.run_rpass_test();
         } else if revision.starts_with("rfail") {
-            if revision_cx.props.should_ice {
-                revision_cx.fatal("can only use should-ice in cfail tests");
+            if self.props.should_ice {
+                self.fatal("can only use should-ice in cfail tests");
             }
-            revision_cx.run_rfail_test();
+            self.run_rfail_test();
         } else if revision.starts_with("cfail") {
-            revision_cx.run_cfail_test();
+            self.run_cfail_test();
         } else {
-            revision_cx.fatal("revision name must begin with rpass, rfail, or cfail");
+            self.fatal("revision name must begin with rpass, rfail, or cfail");
         }
     }
 
-    /// Directory where incremental work products are stored.
-    fn incremental_dir(&self) -> PathBuf {
-        self.output_base_name().with_extension("inc")
-    }
-
     fn run_rmake_test(&self) {
         let cwd = env::current_dir().unwrap();
         let src_root = self.config.src_base.parent().unwrap().parent().unwrap().parent().unwrap();