add missing source_location for assignments generated for initializers

regression/cbmc-cover/location-multiline-statement/multi-file.desc

@@ -3,7 +3,7 @@ multi-file.c
 --cover location
 ^EXIT=0$
 ^SIGNAL=0$
-^\[main.coverage.2\] file multi-file.c line 13 function main block 2 \(lines [\w\- /\.\\:]*dereference.h:main:2; multi-file.c:main:10,13,14,16\): SATISFIED
+^\[main.coverage.2\] file multi-file.c line 10 function main block 2 \(lines [\w\- /\.\\:]*dereference.h:main:2; multi-file.c:main:10,13,14,16\): SATISFIED
 --
 ^warning: ignoring
 --

regression/cbmc-cover/location-multiline-statement/test.desc

@@ -3,7 +3,7 @@ example.c
 --cover location
 ^EXIT=0$
 ^SIGNAL=0$
-^\[main.coverage.2\] file example.c line 13 function main block 2 \(lines example.c:main:10,13,14\): SATISFIED$
+^\[main.coverage.2\] file example.c line 10 function main block 2 \(lines example.c:main:10,13,14\): SATISFIED$
 --
 ^warning: ignoring
 --

regression/cbmc-cover/location15/test.desc

@@ -4,7 +4,7 @@ main.c
 ^EXIT=0$
 ^SIGNAL=0$
 ^\[main.coverage.1\] file main.c line 10 function main block 1.*: SATISFIED$
-^\[main.coverage.2\] file main.c line 11 function main block 2.*: SATISFIED$
+^\[main.coverage.2\] file main.c line 10 function main block 2.*: SATISFIED$
 ^\[main.coverage.3\] file main.c line 13 function main block 3.*: FAILED$
 ^\[main.coverage.4\] file main.c line 16 function main block 4.*: SATISFIED$
 ^\[foo.coverage.1\] file main.c line 5 function foo block 1.*: FAILED$

src/goto-programs/goto_convert.cpp

@@ -637,12 +637,13 @@ void goto_convertt::convert_frontend_decl(
     // Decl must be visible before initializer.
     copy(tmp, DECL, dest);
 
+    auto initializer_location = initializer.find_source_location();
     clean_expr(initializer, dest, mode);
 
     if(initializer.is_not_nil())
     {
       code_assignt assign(code.op0(), initializer);
-      assign.add_source_location() = initializer.find_source_location();
+      assign.add_source_location() = initializer_location;
 
       convert_assign(assign, dest, mode);
     }