Address review comments

Author: owen-mc

go/ql/lib/semmle/go/controlflow/ControlFlowGraph.qll

@@ -50,11 +50,7 @@ module ControlFlow {
     predicate isJoin() { strictcount(this.getAPredecessor()) > 1 }
 
     /** Holds if this is the first control-flow node in `subtree`. */
-    predicate isFirstNodeOf(AstNode subtree) {
-      this.isBefore(subtree)
-      or
-      this.injects(subtree)
-    }
+    predicate isFirstNodeOf(AstNode subtree) { this.isBefore(subtree) }
 
     /** Holds if this node is the unique entry node of a file or function. */
     predicate isEntryNode() { this instanceof CfgImpl::ControlFlow::EntryNode }

go/ql/lib/semmle/go/controlflow/ControlFlowGraphShared.qll

@@ -164,8 +164,6 @@ module CfgImpl {
         not this = any(Go::SelectStmt sel).getBody()
       }
 
-      override Stmt getStmt(int n) { result = Go::BlockStmt.super.getStmt(n) }
-
       Stmt getLastStmt() {
         exists(int last | result = this.getStmt(last) and not exists(this.getStmt(last + 1)))
       }
@@ -183,10 +181,8 @@ module CfgImpl {
       Expr getExpr() { result = Go::ExprStmt.super.getExpr() }
     }
 
-    class IfStmt extends Stmt {
-      IfStmt() { this instanceof Go::IfStmt }
-
-      Expr getCondition() { result = this.(Go::IfStmt).getCond() }
+    class IfStmt extends Stmt instanceof Go::IfStmt {
+      Expr getCondition() { result = this.(Go::IfStmt).getCondition() }
 
       Stmt getThen() { result = this.(Go::IfStmt).getThen() }
 
@@ -195,9 +191,7 @@ module CfgImpl {
 
     AstNode getIfInit(IfStmt ifstmt) { result = ifstmt.(Go::IfStmt).getInit() }
 
-    class LoopStmt extends Stmt {
-      LoopStmt() { this instanceof Go::LoopStmt }
-
+    class LoopStmt extends Stmt instanceof Go::LoopStmt {
       Stmt getBody() { result = this.(Go::LoopStmt).getBody() }
     }
 
@@ -219,19 +213,15 @@ module CfgImpl {
       Expr getCondition() { none() }
     }
 
-    class ForStmt extends LoopStmt {
-      ForStmt() { this instanceof Go::ForStmt }
-
+    class ForStmt extends LoopStmt instanceof Go::ForStmt {
       AstNode getInit(int index) { index = 0 and result = this.(Go::ForStmt).getInit() }
 
       Expr getCondition() { result = this.(Go::ForStmt).getCond() }
 
       AstNode getUpdate(int index) { index = 0 and result = this.(Go::ForStmt).getPost() }
     }
 
-    class ForeachStmt extends LoopStmt {
-      ForeachStmt() { this instanceof Go::RangeStmt }
-
+    class ForeachStmt extends LoopStmt instanceof Go::RangeStmt {
       // Go's `range` statement binds its key and value by destructuring the
       // current element. The extractor synthesizes a single "range element"
       // node grouping the key and value (see `Go::RangeElementExpr`), which we
@@ -249,9 +239,7 @@ module CfgImpl {
 
     class GotoStmt = Go::GotoStmt;
 
-    class ReturnStmt extends Go::ReturnStmt {
-      override Expr getExpr() { result = Go::ReturnStmt.super.getExpr() }
-    }
+    class ReturnStmt = Go::ReturnStmt;
 
     class Throw extends AstNode {
       Throw() { none() }
@@ -281,9 +269,7 @@ module CfgImpl {
       Stmt getBody() { none() }
     }
 
-    class Switch extends AstNode {
-      Switch() { this instanceof Go::SwitchStmt }
-
+    class Switch extends AstNode instanceof Go::SwitchStmt {
       Expr getExpr() {
         result = this.(Go::ExpressionSwitchStmt).getExpr()
         or