Adding upstream version 1.20.14.upstream/1.20.14upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 99 insertions, 0 deletions

diff --git a/src/go/types/eval.go b/src/go/types/eval.go
new file mode 100644
index 0000000..084f746
--- /dev/null
+++ b/src/go/types/eval.go
@@ -0,0 +1,99 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package types
+
+import (
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+)
+
+// Eval returns the type and, if constant, the value for the
+// expression expr, evaluated at position pos of package pkg,
+// which must have been derived from type-checking an AST with
+// complete position information relative to the provided file
+// set.
+//
+// The meaning of the parameters fset, pkg, and pos is the
+// same as in CheckExpr. An error is returned if expr cannot
+// be parsed successfully, or the resulting expr AST cannot be
+// type-checked.
+func Eval(fset *token.FileSet, pkg *Package, pos token.Pos, expr string) (_ TypeAndValue, err error) {
+	// parse expressions
+	node, err := parser.ParseExprFrom(fset, "eval", expr, 0)
+	if err != nil {
+		return TypeAndValue{}, err
+	}
+
+	info := &Info{
+		Types: make(map[ast.Expr]TypeAndValue),
+	}
+	err = CheckExpr(fset, pkg, pos, node, info)
+	return info.Types[node], err
+}
+
+// CheckExpr type checks the expression expr as if it had appeared at position
+// pos of package pkg. Type information about the expression is recorded in
+// info. The expression may be an identifier denoting an uninstantiated generic
+// function or type.
+//
+// If pkg == nil, the Universe scope is used and the provided
+// position pos is ignored. If pkg != nil, and pos is invalid,
+// the package scope is used. Otherwise, pos must belong to the
+// package.
+//
+// An error is returned if pos is not within the package or
+// if the node cannot be type-checked.
+//
+// Note: Eval and CheckExpr should not be used instead of running Check
+// to compute types and values, but in addition to Check, as these
+// functions ignore the context in which an expression is used (e.g., an
+// assignment). Thus, top-level untyped constants will return an
+// untyped type rather then the respective context-specific type.
+func CheckExpr(fset *token.FileSet, pkg *Package, pos token.Pos, expr ast.Expr, info *Info) (err error) {
+	// determine scope
+	var scope *Scope
+	if pkg == nil {
+		scope = Universe
+		pos = token.NoPos
+	} else if !pos.IsValid() {
+		scope = pkg.scope
+	} else {
+		// The package scope extent (position information) may be
+		// incorrect (files spread across a wide range of fset
+		// positions) - ignore it and just consider its children
+		// (file scopes).
+		for _, fscope := range pkg.scope.children {
+			if scope = fscope.Innermost(pos); scope != nil {
+				break
+			}
+		}
+		if scope == nil || debug {
+			s := scope
+			for s != nil && s != pkg.scope {
+				s = s.parent
+			}
+			// s == nil || s == pkg.scope
+			if s == nil {
+				return fmt.Errorf("no position %s found in package %s", fset.Position(pos), pkg.name)
+			}
+		}
+	}
+
+	// initialize checker
+	check := NewChecker(nil, fset, pkg, info)
+	check.scope = scope
+	check.pos = pos
+	defer check.handleBailout(&err)
+
+	// evaluate node
+	var x operand
+	check.rawExpr(&x, expr, nil, true) // allow generic expressions
+	check.processDelayed(0)            // incl. all functions
+	check.recordUntyped()
+
+	return nil
+}