Bug 567217 - Avoid incorrect cache hits during the instantiation of alias template instances

Change-Id: I2f21b0a097f9d279b6e32d28acd68091e3b9ad76

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/InstantiationContext.java

@@ -30,6 +30,7 @@ import org.eclipse.cdt.core.dom.ast.cpp.ICPPTypeSpecialization;
  */
 public final class InstantiationContext {
 	private CPPTemplateParameterMap parameterMap;
+	private boolean forDeduction = false;
 	private int packOffset;
 	private final ICPPSpecialization contextSpecialization;
 	private boolean expandPack;
@@ -78,6 +79,15 @@ public final class InstantiationContext {
 		this(parameterMap, -1, null);
 	}
 
+	/**
+	 * Create an InstantiationContext for a template parameter map, for use template argument deduction.
+	 */
+	public static InstantiationContext forDeduction(ICPPTemplateParameterMap parameterMap) {
+		InstantiationContext result = new InstantiationContext(parameterMap);
+		result.forDeduction = true;
+		return result;
+	}
+
 	/**
 	 * Returns the mapping of template parameters to arguments, possibly {@code null} if the context doesn't
 	 * contain it.
@@ -86,6 +96,13 @@ public final class InstantiationContext {
 		return parameterMap;
 	}
 
+	/**
+	 * Returns whether the InstantiationContext was created during template argument deduction.
+	 */
+	public boolean isForDeduction() {
+		return forDeduction;
+	}
+
 	/**
 	 * Adds a parameter mapping.
 	 */

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

@@ -135,7 +135,7 @@ public class TemplateArgumentDeduction {
 					break;
 				}
 
-				par = CPPTemplates.instantiateType(par, new InstantiationContext(map));
+				par = CPPTemplates.instantiateType(par, InstantiationContext.forDeduction(map));
 				if (!SemanticUtil.isValidType(par))
 					return false;
 
@@ -352,7 +352,7 @@ public class TemplateArgumentDeduction {
 			return null;
 
 		IType par = template.getType();
-		InstantiationContext context = new InstantiationContext(map);
+		InstantiationContext context = InstantiationContext.forDeduction(map);
 		par = CPPTemplates.instantiateType(par, context);
 		if (!SemanticUtil.isValidType(par))
 			return null;
@@ -399,7 +399,7 @@ public class TemplateArgumentDeduction {
 			return null;
 		}
 
-		InstantiationContext context = new InstantiationContext(map);
+		InstantiationContext context = InstantiationContext.forDeduction(map);
 		for (int i = 0; i < length; i++) {
 			if (result[i] == null) {
 				final ICPPTemplateParameter tpar = tmplParams[i];
@@ -427,7 +427,7 @@ public class TemplateArgumentDeduction {
 			return null;
 
 		IType a = SemanticUtil.getSimplifiedType(ftype);
-		InstantiationContext context = new InstantiationContext(map);
+		InstantiationContext context = InstantiationContext.forDeduction(map);
 		IType p = CPPTemplates.instantiateType(template.getType(), context);
 		if (!SemanticUtil.isValidType(p))
 			return null;
@@ -759,7 +759,7 @@ public class TemplateArgumentDeduction {
 
 	private static boolean verifyDeduction(ICPPTemplateParameter[] pars, CPPTemplateParameterMap tpMap,
 			boolean useDefaults) {
-		InstantiationContext context = new InstantiationContext(tpMap);
+		InstantiationContext context = InstantiationContext.forDeduction(tpMap);
 		for (ICPPTemplateParameter tpar : pars) {
 			if (tpar.isParameterPack()) {
 				ICPPTemplateArgument[] deducedArgs = tpMap.getPackExpansion(tpar);
@@ -1022,7 +1022,7 @@ public class TemplateArgumentDeduction {
 					return true; // An unknown type may match anything.
 
 				// Verify that the resolved binding matches the argument type.
-				InstantiationContext context = new InstantiationContext(fDeducedArgs);
+				InstantiationContext context = InstantiationContext.forDeduction(fDeducedArgs);
 				IBinding binding = CPPTemplates.resolveUnknown((ICPPUnknownBinding) p, context);
 				if (binding instanceof ICPPUnknownBinding)
 					return true; // An unknown type may match anything.

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

@@ -21,6 +21,7 @@ import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateArgument;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateParameterMap;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPTypeSpecialization;
 import org.eclipse.cdt.core.parser.util.CharArrayUtils;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPTemplateParameterMap;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.InstantiationContext;
 import org.eclipse.core.runtime.CoreException;
 
@@ -36,7 +37,15 @@ public class TypeInstantiationRequest {
 
 	public TypeInstantiationRequest(IType type, InstantiationContext context) {
 		this.type = type;
-		this.parameterMap = context.getParameterMap();
+		/*
+		 * If the InstantiationContext was created during template argument deduction, its parameter map
+		 * can be modified later in the deduction process. Since the TypeInstantiationRequest is used
+		 * as a key in various caches, we don't want the map changing after constructing this object,
+		 * so clone the map is such cases.
+		 */
+		this.parameterMap = context.isForDeduction()
+				? new CPPTemplateParameterMap((CPPTemplateParameterMap) context.getParameterMap())
+				: context.getParameterMap();
 		this.packOffset = context.getPackOffset();
 		this.contextTypeSpecialization = context.getContextTypeSpecialization();
 	}