Reuse cached layout from PostAnalysis when possible.

Author: cjgillot

compiler/rustc_ty_utils/src/layout.rs

@@ -66,6 +66,24 @@ fn layout_of<'tcx>(
         return tcx.layout_of(typing_env.as_query_input(ty));
     }
 
+    match typing_env.typing_mode() {
+        ty::TypingMode::Codegen => {
+            let with_postanalysis =
+                ty::TypingEnv::new(typing_env.param_env, ty::TypingMode::PostAnalysis);
+            let res = tcx.layout_of(with_postanalysis.as_query_input(ty));
+            match res {
+                Err(LayoutError::TooGeneric(_)) => {}
+                _ => return res,
+            };
+        }
+        ty::TypingMode::Coherence
+        | ty::TypingMode::Analysis { .. }
+        | ty::TypingMode::Borrowck { .. }
+        | ty::TypingMode::PostBorrowckAnalysis { .. }
+        | ty::TypingMode::ErasedNotCoherence(_)
+        | ty::TypingMode::PostAnalysis => {}
+    }
+
     let cx = LayoutCx::new(tcx, typing_env);
 
     let layout = layout_of_uncached(&cx, ty)?;

tests/ui/recursion/recursion_limit/zero-overflow.rs

@@ -1,4 +1,4 @@
-//~ ERROR overflow evaluating the requirement `&mut Self: DispatchFromDyn<&mut RustaceansAreAwesome>
+//~ ERROR queries overflow the depth limit!
 //~| HELP consider increasing the recursion limit
 //@ build-fail
 

tests/ui/recursion/recursion_limit/zero-overflow.stderr

@@ -1,7 +1,7 @@
-error[E0275]: overflow evaluating the requirement `&mut Self: DispatchFromDyn<&mut RustaceansAreAwesome>`
+error: queries overflow the depth limit!
    |
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "2"]` attribute to your crate (`zero_overflow`)
+   = note: query depth increased by 2 when computing layout of `isize`
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0275`.