Make source locations for standard library calls explicit

Author: adrian-prantl

lib/SILGen/SILGenApply.cpp

@@ -5935,6 +5935,10 @@ RValue SILGenFunction::emitApplyOfLibraryIntrinsic(SILLocation loc,
                                                    SubstitutionMap subMap,
                                                    ArrayRef<ManagedValue> args,
                                                    SGFContext ctx) {
+  // Calls into library intrinsics are implicitly generated by the compiler.
+  // Marking them as explicit creates a backtrace pointing back to the user code
+  // that the intrinsic call was generated from.
+  loc.markExplicit();
   auto callee = Callee::forDirect(*this, declRef, subMap, loc);
 
   auto origFormalType = callee.getOrigFormalType();

test/DebugInfo/iuo_assertloc.swift

@@ -0,0 +1,10 @@
+// RUN: %target-swift-frontend %s -emit-sil -parse-as-library -g -o - | %FileCheck %s --check-prefix=CHECK-SIL
+// RUN: %target-swift-frontend %s -emit-ir -parse-as-library -g -o - | %FileCheck %s --check-prefix=CHECK-IR
+
+public func f(_ a: Int!) -> Int {
+  // CHECK-IR: call {{.*}}assertionFailure{{.*}}, !dbg ![[LOC:[0-9]+]]
+  // CHECK-IR: ![[LOC]] = !DILocation(line: [[@LINE+1]], column: 11
+  return (a // CHECK-SIL: apply {{.*}}:[[@LINE]]:11
+          +
+          1)
+}