C#: Improve various join orders

Author: hvitved

csharp/ql/src/semmle/code/csharp/Conversion.qll

@@ -601,11 +601,12 @@ private predicate convArrayTypeCovariance(ArrayType fromType, ArrayType toType)
   convArrayTypeCovarianceJoin(fromType, toType, toType.getDimension(), toType.getRank())
 }
 
-pragma[noinline]
+pragma[nomagic]
 private predicate convArrayTypeCovarianceJoin(ArrayType fromType, ArrayType toType, int dim, int rnk) {
   convArrayElementType(fromType, toType.getElementType(), dim, rnk)
 }
 
+pragma[nomagic]
 private predicate convArrayElementType(ArrayType at, ArrayElementType aet, int dim, int rnk) {
   convRefTypeNonNull(at.getElementType(), aet) and
   dim = at.getDimension() and

csharp/ql/src/semmle/code/csharp/controlflow/Guards.qll

@@ -261,6 +261,12 @@ module AbstractValues {
 
 private import AbstractValues
 
+pragma[nomagic]
+private predicate typePattern(PatternMatch pm, TypePatternExpr tpe, Type t) {
+  tpe = pm.getPattern() and
+  t = pm.getExpr().getType()
+}
+
 /**
  * An expression that evaluates to a value that can be dereferenced. That is,
  * an expression that may evaluate to `null`.
@@ -337,19 +343,23 @@ class DereferenceableExpr extends Expr {
       or
       result =
         any(PatternMatch pm |
-          pm.getExpr() = this and
-          if pm.getPattern() instanceof NullLiteral
-          then
+          this = pm.getExpr() and
+          (
             // E.g. `x is null`
+            pm.getPattern() instanceof NullLiteral and
             isNull = branch
-          else (
+            or
             // E.g. `x is string` or `x is ""`
-            branch = true and isNull = false
+            not pm.getPattern() instanceof NullLiteral and
+            branch = true and
+            isNull = false
             or
-            // E.g. `x is string` where `x` has type `string`
-            pm.getPattern().(TypePatternExpr).getCheckedType() = pm.getExpr().getType() and
-            branch = false and
-            isNull = true
+            exists(TypePatternExpr tpe |
+              // E.g. `x is string` where `x` has type `string`
+              typePattern(result, tpe, tpe.getCheckedType()) and
+              branch = false and
+              isNull = true
+            )
           )
         )
       or

csharp/ql/src/semmle/code/csharp/controlflow/internal/Completion.qll

@@ -388,9 +388,16 @@ private class TriedControlFlowElement extends ControlFlowElement {
   }
 }
 
-pragma[noinline]
+pragma[nomagic]
+private ValueOrRefType getACastExprBaseType(CastExpr ce) {
+  result = ce.getType().(ValueOrRefType).getABaseType()
+  or
+  result = getACastExprBaseType(ce).getABaseType()
+}
+
+pragma[nomagic]
 private predicate invalidCastCandidate(CastExpr ce) {
-  ce.getType() = ce.getExpr().getType().(ValueOrRefType).getASubType+()
+  ce.getExpr().getType() = getACastExprBaseType(ce)
 }
 
 private predicate assertion(Assertion a, int i, AssertMethod am, Expr e) {

csharp/ql/src/semmle/code/csharp/dataflow/SSA.qll

@@ -1820,11 +1820,12 @@ module Ssa {
       BasicBlock bb, int i, LocalScopeSourceVariable v, ImplicitEntryDefinition def,
       ControlFlow::Nodes::ElementNode c, boolean additionalCalls
     ) {
-      exists(Callable reader |
+      exists(Callable reader, SourceVariable sv |
         implicitReadCandidate(bb, i, c, v) and
         readsCapturedVariable(c, v, reader, additionalCalls) and
-        def.getCallable() = reader and
-        def.getSourceVariable().getAssignable() = v.getAssignable()
+        sv = def.getSourceVariable() and
+        reader = sv.getEnclosingCallable() and
+        v.getAssignable() = sv.getAssignable()
       )
     }