Introduce Parameter::getAVariable()

ql/src/codeql_ruby/ast/Parameter.qll

@@ -21,6 +21,15 @@ class Parameter extends AstNode {
 
   /** Gets the zero-based position of this parameter. */
   final int getPosition() { result = pos }
+
+  /** Gets a variable introduced by this parameter. */
+  Variable getAVariable() { none() }
+
+  /** Gets the variable named `name` introduced by this parameter. */
+  final Variable getVariable(string name) {
+    result = this.getAVariable() and
+    result.getName() = name
+  }
 }
 
 /**
@@ -33,6 +42,10 @@ class PatternParameter extends Parameter, Pattern { }
 /** A parameter defined using a tuple pattern. */
 class TuplePatternParameter extends PatternParameter, TuplePattern {
   final override string describeQlClass() { result = "TuplePatternParameter" }
+
+  final override Variable getAVariable() {
+    result = this.getAnElement+().(VariablePattern).getVariable()
+  }
 }
 
 /** A named parameter. */
@@ -45,6 +58,8 @@ class NamedParameter extends Parameter {
   /** Gets the variable introduced by this parameter. */
   Variable getVariable() { none() }
 
+  final override Variable getAVariable() { result = this.getVariable() }
+
   /** Gets an access to this parameter. */
   final VariableAccess getAnAccess() { result = this.getVariable().getAnAccess() }
 }

ql/src/codeql_ruby/ast/Pattern.qll

@@ -2,6 +2,7 @@ import codeql_ruby.AST
 private import codeql_ruby.Generated
 private import codeql.Locations
 private import internal.Pattern
+private import internal.Variable
 private import Variable
 
 /** A pattern. */
@@ -16,8 +17,8 @@ class VariablePattern extends Pattern {
   /** Gets the name of the variable used in this pattern. */
   final string getVariableName() { result = generated.getValue() }
 
-  /** Gets the variable used in this pattern. */
-  Variable getVariable() { this = result.getAnAccess() }
+  /** Gets the variable used in (or introduced by) this pattern. */
+  Variable getVariable() { access(this, result) }
 
   override string toString() { result = this.getVariableName() }
 }

ql/src/codeql_ruby/ast/Variable.qll

@@ -60,7 +60,11 @@ class VariableAccess extends AstNode, @token_identifier {
   override Generated::Identifier generated;
   Variable variable;
 
-  VariableAccess() { access(this, variable) }
+  VariableAccess() {
+    access(this, variable) and
+    // Do not generate an access at the defining location
+    not variable = TLocalVariable(_, _, this)
+  }
 
   /** Gets the variable this identifier refers to. */
   Variable getVariable() { result = variable }

ql/src/codeql_ruby/ast/internal/Variable.qll

@@ -123,11 +123,7 @@ private module Cached {
 
   cached
   predicate access(Generated::Identifier access, Variable variable) {
-    exists(string name |
-      name = access.getValue() and
-      // Do not generate an access at the defining location
-      not variable = TLocalVariable(_, name, access)
-    |
+    exists(string name | name = access.getValue() |
       variable = enclosingScope(access).getVariable(name) and
       not strictlyBefore(access.getLocation(), variable.getLocation())
       or