[move-only] Avoid loc from func decl.

It's always the first line of the function, so try to do better.

Author: nate-chandler

lib/SILOptimizer/Mandatory/MoveOnlyDiagnostics.cpp

@@ -14,6 +14,7 @@
 
 #include "MoveOnlyDiagnostics.h"
 
+#include "swift/AST/Decl.h"
 #include "swift/AST/DiagnosticsSIL.h"
 #include "swift/AST/Stmt.h"
 #include "swift/Basic/Defer.h"
@@ -226,6 +227,12 @@ void DiagnosticEmitter::emitMissingConsumeInDiscardingContext(
       return true;
 
     case SILLocation::RegularKind: {
+      Decl *decl = loc.getAsASTNode<Decl>();
+      if (decl && isa<AbstractFunctionDecl>(decl)) {
+        // Having the function itself as a location results in a location at the
+        // first line of the function.  Find another location.
+        return false;
+      }
       Stmt *stmt = loc.getAsASTNode<Stmt>();
       if (!stmt)
         return true; // For non-statements, assume it is exiting the func.

test/SILOptimizer/discard_checking.swift

@@ -165,7 +165,7 @@ struct Basics: ~Copyable {
     }
   }
 
-  consuming func test8_stillMissingAConsume1(_ c: Color) throws { // expected-error {{must consume 'self' before exiting method that discards self}}
+  consuming func test8_stillMissingAConsume1(_ c: Color) throws {
     if case .red = c {
       discard self // expected-note {{discarded self here}}
       return
@@ -174,7 +174,7 @@ struct Basics: ~Copyable {
       _ = consume self
       fatalError("hi")
     }
-  }
+  } // expected-error {{must consume 'self' before exiting method that discards self}}
 
   consuming func test8_stillMissingAConsume2(_ c: Color) throws {
     if case .red = c {
@@ -251,7 +251,7 @@ struct Basics: ~Copyable {
     }
   }
 
-  consuming func test11(_ c: Color) { // expected-error {{must consume 'self' before exiting method that discards self}}
+  consuming func test11(_ c: Color) {
     guard case .red = c else {
       discard self // expected-note {{discarded self here}}
       return
@@ -264,7 +264,7 @@ struct Basics: ~Copyable {
     let x = self
     self = x
     mutator()
-  }
+  } // expected-error {{must consume 'self' before exiting method that discards self}}
 
   consuming func test11_fixed(_ c: Color) {
     guard case .red = c else {
@@ -328,13 +328,13 @@ struct Basics: ~Copyable {
     _ = consume self
   }
 
-  consuming func test13(_ c: Color) async { // expected-error {{must consume 'self' before exiting method that discards self}}
+  consuming func test13(_ c: Color) async {
     guard case .red = c else {
       discard self // expected-note {{discarded self here}}
       return
     }
     await asyncer()
-  }
+  } // expected-error {{must consume 'self' before exiting method that discards self}}
 
   consuming func test13_fixed(_ c: Color) async {
     guard case .red = c else {
@@ -345,7 +345,7 @@ struct Basics: ~Copyable {
     _ = consume self
   }
 
-  consuming func test14(_ c: Color) async { // expected-error {{must consume 'self' before exiting method that discards self}}
+  consuming func test14(_ c: Color) async {
     guard case .red = c else {
       discard self // expected-note {{discarded self here}}
       return
@@ -354,7 +354,7 @@ struct Basics: ~Copyable {
       cont.resume()
     }
     print("back!")
-  }
+  } // expected-error {{must consume 'self' before exiting method that discards self}}
 
   consuming func test14_fixed(_ c: Color) async {
     guard case .red = c else {