[clang][frontend] Require invocation to construct `CompilerInstance` (#137668)

This PR makes it so that `CompilerInvocation` needs to be provided to
`CompilerInstance` on construction. There are a couple of benefits in my
view:
* Making it impossible to mis-use some `CompilerInstance` APIs. For
example there are cases, where `createDiagnostics()` was called before
`setInvocation()`, causing the `DiagnosticEngine` to use the
default-constructed `DiagnosticOptions` instead of the intended ones.
* This shrinks `CompilerInstance`'s state space.
* This makes it possible to access **the** invocation in
`CompilerInstance`'s constructor (to be used in a follow-up).

1 files changed, 2 insertions, 4 deletions

diff --git a/clang/unittests/Serialization/ForceCheckFileInputTest.cpp b/clang/unittests/Serialization/ForceCheckFileInputTest.cpp
index 6a839d1..16742a6 100644
--- a/clang/unittests/Serialization/ForceCheckFileInputTest.cpp
+++ b/clang/unittests/Serialization/ForceCheckFileInputTest.cpp
@@ -86,9 +86,8 @@ export int aa = 43;
 
     Buf->release();
 
-    CompilerInstance Instance;
+    CompilerInstance Instance(std::move(Invocation));
     Instance.setDiagnostics(Diags.get());
-    Instance.setInvocation(Invocation);
 
     Instance.getFrontendOpts().OutputFile = BMIPath;
 
@@ -121,9 +120,8 @@ export int aa = 43;
     EXPECT_TRUE(Invocation);
     Invocation->getFrontendOpts().DisableFree = false;
 
-    CompilerInstance Clang;
+    CompilerInstance Clang(std::move(Invocation));
 
-    Clang.setInvocation(Invocation);
     Clang.setDiagnostics(Diags.get());
     FileManager *FM = Clang.createFileManager(CIOpts.VFS);
     Clang.createSourceManager(*FM);