Function mergeLexicalEnvironment

test/fixtures/snapshot/typescript.js:27083–27163

(statements, declarations)

            return i;
        }
        function mergeLexicalEnvironment(statements, declarations) {
            if (!ts.some(declarations)) {
                return statements;
            }
            // When we merge new lexical statements into an existing statement list, we merge them in the following manner:
            //
            // Given:
            //
            // | Left                               | Right                               |
            // |------------------------------------|-------------------------------------|
            // | [standard prologues (left)]        | [standard prologues (right)]        |
            // | [hoisted functions (left)]         | [hoisted functions (right)]         |
            // | [hoisted variables (left)]         | [hoisted variables (right)]         |
            // | [lexical init statements (left)]   | [lexical init statements (right)]   |
            // | [other statements (left)]          |                                     |
            //
            // The resulting statement list will be:
            //
            // | Result                              |
            // |-------------------------------------|
            // | [standard prologues (right)]        |
            // | [standard prologues (left)]         |
            // | [hoisted functions (right)]         |
            // | [hoisted functions (left)]          |
            // | [hoisted variables (right)]         |
            // | [hoisted variables (left)]          |
            // | [lexical init statements (right)]   |
            // | [lexical init statements (left)]    |
            // | [other statements (left)]           |
            //
            // NOTE: It is expected that new lexical init statements must be evaluated before existing lexical init statements,
            // as the prior transformation may depend on the evaluation of the lexical init statements to be in the correct state.
            // find standard prologues on left in the following order: standard directives, hoisted functions, hoisted variables, other custom
            var leftStandardPrologueEnd = findSpanEnd(statements, ts.isPrologueDirective, 0);
            var leftHoistedFunctionsEnd = findSpanEnd(statements, ts.isHoistedFunction, leftStandardPrologueEnd);
            var leftHoistedVariablesEnd = findSpanEnd(statements, ts.isHoistedVariableStatement, leftHoistedFunctionsEnd);
            // find standard prologues on right in the following order: standard directives, hoisted functions, hoisted variables, other custom
            var rightStandardPrologueEnd = findSpanEnd(declarations, ts.isPrologueDirective, 0);
            var rightHoistedFunctionsEnd = findSpanEnd(declarations, ts.isHoistedFunction, rightStandardPrologueEnd);
            var rightHoistedVariablesEnd = findSpanEnd(declarations, ts.isHoistedVariableStatement, rightHoistedFunctionsEnd);
            var rightCustomPrologueEnd = findSpanEnd(declarations, ts.isCustomPrologue, rightHoistedVariablesEnd);
            ts.Debug.assert(rightCustomPrologueEnd === declarations.length, "Expected declarations to be valid standard or custom prologues");
            // splice prologues from the right into the left. We do this in reverse order
            // so that we don't need to recompute the index on the left when we insert items.
            var left = ts.isNodeArray(statements) ? statements.slice() : statements;
            // splice other custom prologues from right into left
            if (rightCustomPrologueEnd > rightHoistedVariablesEnd) {
                left.splice.apply(left, __spreadArray([leftHoistedVariablesEnd, 0], declarations.slice(rightHoistedVariablesEnd, rightCustomPrologueEnd), false));
            }
            // splice hoisted variables from right into left
            if (rightHoistedVariablesEnd > rightHoistedFunctionsEnd) {
                left.splice.apply(left, __spreadArray([leftHoistedFunctionsEnd, 0], declarations.slice(rightHoistedFunctionsEnd, rightHoistedVariablesEnd), false));
            }
            // splice hoisted functions from right into left
            if (rightHoistedFunctionsEnd > rightStandardPrologueEnd) {
                left.splice.apply(left, __spreadArray([leftStandardPrologueEnd, 0], declarations.slice(rightStandardPrologueEnd, rightHoistedFunctionsEnd), false));
            }
            // splice standard prologues from right into left (that are not already in left)