refactor fn bootstrap::builder::Builder::compiler_for logic

src/bootstrap/builder.rs

@@ -919,9 +919,9 @@ impl<'a> Builder<'a> {
         host: TargetSelection,
         target: TargetSelection,
     ) -> Compiler {
-        if self.build.force_use_stage2() {
+        if self.build.force_use_stage2(stage) {
             self.compiler(2, self.config.build)
-        } else if self.build.force_use_stage1(Compiler { stage, host }, target) {
+        } else if self.build.force_use_stage1(stage, target) {
             self.compiler(1, self.config.build)
         } else {
             self.compiler(stage, host)

src/bootstrap/lib.rs

@@ -1198,19 +1198,20 @@ impl Build {
     ///
     /// When all of these conditions are met the build will lift artifacts from
     /// the previous stage forward.
-    fn force_use_stage1(&self, compiler: Compiler, target: TargetSelection) -> bool {
+    fn force_use_stage1(&self, stage: u32, target: TargetSelection) -> bool {
         !self.config.full_bootstrap
-            && compiler.stage >= 2
+            && !self.config.download_rustc()
+            && stage >= 2
             && (self.hosts.iter().any(|h| *h == target) || target == self.build)
     }
 
     /// Checks whether the `compiler` compiling for `target` should be forced to
     /// use a stage2 compiler instead.
     ///
-    /// When we download the pre-compiled version of rustc it should be forced to
-    /// use a stage2 compiler.
-    fn force_use_stage2(&self) -> bool {
-        self.config.download_rustc()
+    /// When we download the pre-compiled version of rustc and compiler stage is >= 2,
+    /// it should be forced to use a stage2 compiler.
+    fn force_use_stage2(&self, stage: u32) -> bool {
+        self.config.download_rustc() && stage >= 2
     }
 
     /// Given `num` in the form "a.b.c" return a "release string" which