Add location for implicitly declared variables

Author: owen-mc

go/ql/lib/semmle/go/Scopes.qll

@@ -148,15 +148,22 @@ class Entity extends @object {
     string filepath, int startline, int startcolumn, int endline, int endcolumn
   ) {
     // take the location of the declaration if there is one
-    this.getDeclaration().hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
-    or
-    // otherwise fall back on dummy location
-    not exists(this.getDeclaration()) and
-    filepath = "" and
-    startline = 0 and
-    startcolumn = 0 and
-    endline = 0 and
-    endcolumn = 0
+    if exists(this.getDeclaration())
+    then this.getDeclaration().hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
+    else
+      // take the location of the implicit declaration if there is one
+      if this = any(CaseClause cc).getImplicitlyDeclaredVariable()
+      then
+        any(CaseClause cc | this = cc.getImplicitlyDeclaredVariable())
+            .hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
+      else (
+        // otherwise fall back on dummy location
+        filepath = "" and
+        startline = 0 and
+        startcolumn = 0 and
+        endline = 0 and
+        endcolumn = 0
+      )
   }
 }