Rollup merge of rust-lang#55495 - wesleywiser:opt_fuel_rustbuild, r=nikomatsakis

Don't print opt fuel messages to stdout because it breaks Rustbuild

Rustbuild passes `--message-format json` to the compiler invocations
which causes JSON to be emitted on stdout. Printing optimization fuel
messages to stdout breaks the json and causes Rustbuild to fail.

Work around this by emitting optimization fuel related messages on
stderr instead.

Author: kennytm

src/librustc/session/mod.rs

@@ -868,7 +868,7 @@ impl Session {
                 let fuel = self.optimization_fuel_limit.get();
                 ret = fuel != 0;
                 if fuel == 0 && !self.out_of_fuel.get() {
-                    println!("optimization-fuel-exhausted: {}", msg());
+                    eprintln!("optimization-fuel-exhausted: {}", msg());
                     self.out_of_fuel.set(true);
                 } else if fuel > 0 {
                     self.optimization_fuel_limit.set(fuel - 1);

src/librustc_driver/lib.rs

@@ -952,7 +952,7 @@ impl<'a> CompilerCalls<'a> for RustcDefaultCalls {
             control.compilation_done.callback = box move |state| {
                 old_callback(state);
                 let sess = state.session;
-                println!("Fuel used by {}: {}",
+                eprintln!("Fuel used by {}: {}",
                     sess.print_fuel_crate.as_ref().unwrap(),
                     sess.print_fuel.get());
             }

src/test/run-pass/optimization-fuel-0.rs

@@ -12,7 +12,8 @@
 
 use std::mem::size_of;
 
-// compile-flags: -Z fuel=foo=0
+// (#55495: The --error-format is to sidestep an issue in our test harness)
+// compile-flags: --error-format human -Z fuel=foo=0
 
 struct S1(u8, u16, u8);
 struct S2(u8, u16, u8);

src/test/run-pass/optimization-fuel-0.stdout renamed to src/test/run-pass/optimization-fuel-0.stderr

@@ -12,7 +12,8 @@
 
 use std::mem::size_of;
 
-// compile-flags: -Z fuel=foo=1
+// (#55495: The --error-format is to sidestep an issue in our test harness)
+// compile-flags: --error-format human -Z fuel=foo=1
 
 struct S1(u8, u16, u8);
 struct S2(u8, u16, u8);

src/test/run-pass/optimization-fuel-1.rs

@@ -11,7 +11,8 @@
 #![crate_name="foo"]
 #![allow(dead_code)]
 
-// compile-flags: -Z print-fuel=foo
+// (#55495: The --error-format is to sidestep an issue in our test harness)
+// compile-flags: --error-format human -Z print-fuel=foo
 // compile-pass
 
 struct S1(u8, u16, u8);