Make sure AST is available to C getExpressionType too

C++ parser methods already store current lookup point which makes AST available
via thread-local variable. Do the same for C parser to enable SizeofCalculator
accessing type size macros via AST while processing C code.

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/ArithmeticConversion.java

@@ -425,6 +425,10 @@ private static long getApproximateSize(IBasicType type) {
 
 	/**
 	 * Checks whether a target integral type can represent all values of a source integral type.
+	 * <br><br>
+	 * If CPPSemantics current lookup point is set, size and alignment information is derived
+	 * from predefined type size macros available through current AST. If there is no current
+	 * lookup point, {@link #getApproximateSize(IBasicType)} is used to guess size of integral types.
 	 *
 	 * @param target the target integral type
 	 * @param source the source integral type

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/c/CASTBinaryExpression.java

@@ -30,6 +30,7 @@
 import org.eclipse.cdt.core.dom.ast.c.ICArrayType;
 import org.eclipse.cdt.internal.core.dom.parser.ASTNode;
 import org.eclipse.cdt.internal.core.dom.parser.IASTAmbiguityParent;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.CPPSemantics;
 
 /**
  * Binary expression for c
@@ -213,6 +214,15 @@ public void replace(IASTNode child, IASTNode other) {
 
 	@Override
 	public IType getExpressionType() {
+		CPPSemantics.pushLookupPoint(this);
+		try {
+			return getExpressionTypeImpl();
+		} finally {
+			CPPSemantics.popLookupPoint();
+		}
+	}
+
+	private IType getExpressionTypeImpl() {
 		final int op = getOperator();
 		IType originalType1 = getOperand1().getExpressionType();
 		IType originalType2 = getOperand2().getExpressionType();

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/c/CASTConditionalExpression.java

@@ -28,6 +28,7 @@
 import org.eclipse.cdt.internal.core.dom.parser.ASTNode;
 import org.eclipse.cdt.internal.core.dom.parser.IASTAmbiguityParent;
 import org.eclipse.cdt.internal.core.dom.parser.ProblemType;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.CPPSemantics;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.ExpressionTypes;
 
 /**
@@ -163,6 +164,15 @@ public void replace(IASTNode child, IASTNode other) {
 
 	@Override
 	public IType getExpressionType() {
+		CPPSemantics.pushLookupPoint(this);
+		try {
+			return getExpressionTypeImpl();
+		} finally {
+			CPPSemantics.popLookupPoint();
+		}
+	}
+
+	private IType getExpressionTypeImpl() {
 		IASTExpression positiveExpression = getPositiveResultExpression();
 		if (positiveExpression == null) {
 			positiveExpression = getLogicalConditionExpression();

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPSemantics.java

@@ -212,6 +212,7 @@
 import org.eclipse.cdt.internal.core.dom.parser.ITypeContainer;
 import org.eclipse.cdt.internal.core.dom.parser.IntegralValue;
 import org.eclipse.cdt.internal.core.dom.parser.ProblemBinding;
+import org.eclipse.cdt.internal.core.dom.parser.SizeofCalculator;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPASTIdExpression;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPASTLiteralExpression;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPASTName;
@@ -323,12 +324,15 @@ public static void popLookupPoint() {
 
 	/**
 	 * Get the current point of instantiation / point of lookup for name lookups.
-	 *
+	 * <br><br>
 	 * NOTE: This is meant to be used primarily for "declaredBefore" purposes, that is,
 	 *       for determining whether something was declared before or after the point
 	 *       of lookup. It is NOT meant to be used as a general mechanism for accessing
 	 *       information about a call site without having to pass that information along
 	 *       the usual way (via function arguments).
+	 * <br><br>
+	 * NOTE: This is also used to provide {@link SizeofCalculator} with access to predefined
+	 *       type size macros of current translation unit via AST object.
 	 */
 	public static IASTNode getCurrentLookupPoint() {
 		Deque<IASTNode> lookupPoints = fLookupPoints.get();