Go: support compound condition guards

Author: owen-mc

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

@@ -31,6 +31,16 @@ private module GuardsInput implements
     CfgImpl::Cfg::BasicBlock getBasicBlock() { result = this.getControlFlowNode().getBasicBlock() }
   }
 
+  predicate booleanOutcomeBlock(Expr guard, CfgImpl::Cfg::BasicBlock outcomeBlock, boolean branch) {
+    exists(CfgImpl::Cfg::ControlFlowNode outcomeNode |
+      branch = true and outcomeNode.isAfterTrue(guard)
+      or
+      branch = false and outcomeNode.isAfterFalse(guard)
+    |
+      outcomeBlock = outcomeNode.getBasicBlock()
+    )
+  }
+
   private newtype TConstantValue = TStringValue(string s) { s = any(G::Expr e).getStringValue() }
 
   class ConstantValue extends TConstantValue {

go/ql/test/library-tests/semmle/go/controlflow/Guards/Guards.expected

@@ -5,6 +5,9 @@ controlsResult
 | guards.go:9:7:9:16 | ...==... | positive | false |
 | guards.go:9:7:9:16 | ...==... | zero | true |
 | guards.go:28:5:28:5 | a | compound true | true |
+| guards.go:28:5:28:17 | ...&&... | compound false | false |
+| guards.go:28:5:28:17 | ...&&... | compound true | true |
+| guards.go:28:11:28:16 | ...\|\|... | compound true | true |
 | guards.go:36:5:36:20 | ...==... | upcast | true |
 | guards.go:39:5:39:19 | ...==... | downcast | true |
 | guards.go:42:5:42:22 | ...==... | upcast narrow | true |
@@ -24,6 +27,9 @@ valueControlsResult
 | guards.go:9:7:9:16 | ...==... | positive | false |
 | guards.go:9:7:9:16 | ...==... | zero | true |
 | guards.go:28:5:28:5 | a | compound true | true |
+| guards.go:28:5:28:17 | ...&&... | compound false | false |
+| guards.go:28:5:28:17 | ...&&... | compound true | true |
+| guards.go:28:11:28:16 | ...\|\|... | compound true | true |
 | guards.go:36:5:36:15 | type conversion | upcast | 0 |
 | guards.go:36:5:36:20 | ...==... | upcast | true |
 | guards.go:36:11:36:14 | wide | upcast | 0 |