Squash this2

Author: Kwstubbs

go/ql/lib/semmle/go/dataflow/SSA.qll

@@ -438,7 +438,32 @@ class SsaPhiNode extends SsaPseudoDefinition, TPhi {
  */
 private newtype TGlobalSsaWithFields =
   TGlobalRoot(SsaGlobalVariable v) or
-  TGlobalStep(GlobalWithFields base, Field f) { exists(accessPathAux(base, f)) }
+  TGlobalStep(GlobalWithFields base, Field f) { exists(accessGlobalPathAux(base, f)) }
+
+
+/**
+ * Gets a representation of `insn` as an ssa-with-fields value if there is one.
+ */
+private TGlobalSsaWithFields accessGlobalPath(IR::Instruction insn) {
+  exists(SsaGlobalVariable v | insn = v.getAUse() | result = TGlobalRoot(v))
+  or
+  exists(GlobalWithFields base, Field f | insn = accessGlobalPathAux(base, f) | result = TGlobalStep(base, f))
+}
+
+/**
+ * Gets a data-flow node that reads a field `f` from a node that is represented
+ * by ssa-with-fields value `base`.
+ */
+private IR::Instruction accessGlobalPathAux(TGlobalSsaWithFields base, Field f) {
+  exists(IR::FieldReadInstruction fr, IR::Instruction frb |
+    fr.getBase() = frb or
+    fr.getBase() = IR::implicitDerefInstruction(frb.(IR::EvalInstruction).getExpr())
+  |
+    base = accessGlobalPath(frb) and
+    f = fr.getField() and
+    result = fr
+  )
+}
 
 /**
  * An SSA variable, possibly with a chain of field reads on it.
@@ -541,34 +566,34 @@ class SsaWithFields extends TSsaWithFields {
 
 
 /** An SSA variable with zero or more fields read from it. */
-class GlobalWithFields extends TSsaWithFields {
+class GlobalWithFields extends TGlobalSsaWithFields {
   /**
    * Gets the SSA variable corresponding to the base of this SSA variable with fields.
    *
    * For example, the SSA variable corresponding to `a` for the SSA variable with fields
    * corresponding to `a.b`.
    */
-  SsaVariable getBaseVariable() {
-    this = TRoot(result)
+  SsaGlobalVariable getBaseVariable() {
+    this = TGlobalRoot(result)
     or
-    exists(GlobalWithFields base | this = TStep(base, _) | result = base.getBaseVariable())
+    exists(GlobalWithFields base | this = TGlobalStep(base, _) | result = base.getBaseVariable())
   }
 
   /** Gets a use that refers to this SSA variable with fields. */
-  DataFlow::Node getAUse() { this = accessPath(result.asInstruction()) }
+  DataFlow::Node getAUse() { this = accessGlobalPath(result.asInstruction()) }
 
   /** Gets the type of this SSA variable with fields. */
   Type getType() {
-    exists(SsaVariable var | this = TRoot(var) | result = var.getType())
+    exists(SsaGlobalVariable var | this = TGlobalRoot(var) | result = var.getType())
     or
-    exists(Field f | this = TStep(_, f) | result = f.getType())
+    exists(Field f | this = TGlobalStep(_, f) | result = f.getType())
   }
 
   /** Gets a textual representation of this element. */
   string toString() {
-    exists(SsaVariable var | this = TRoot(var) | result = "(" + var + ")")
+    exists(SsaGlobalVariable var | this = TGlobalRoot(var) | result = "(" + var + ")")
     or
-    exists(GlobalWithFields base, Field f | this = TStep(base, f) | result = base + "." + f.getName())
+    exists(GlobalWithFields base, Field f | this = TGlobalStep(base, f) | result = base + "." + f.getName())
   }
 
   /**
@@ -587,9 +612,9 @@ class GlobalWithFields extends TSsaWithFields {
    * `"a.b"`.
    */
   string getQualifiedName() {
-    exists(SsaVariable v | this = TRoot(v) and result = v.getSourceVariable().getName())
+    exists(SsaGlobalVariable v | this = TGlobalRoot(v) and result = v.getSourceVariable().getName())
     or
-    exists(GlobalWithFields base, Field f | this = TStep(base, f) |
+    exists(GlobalWithFields base, Field f | this = TGlobalStep(base, f) |
       result = base.getQualifiedName() + "." + f.getName()
     )
   }